Introduction

NOTE: For specifications with illustrations, make reference to Specifications For 3406 And 3406B Generator Set Engines, Form No. SENR2536. If the Specifications in Form SENR2536 are not the same as in the Systems Operation and the Testing And Adjusting, look at the printing date on the back cover of each book. Use the Specifications given in the book with the latest date.

Engine Design

Cylinder And Valve Location

Bore ... 137.2 mm (5.40 in.)

Stroke ... 165.1 mm (6.50 in.)

Displacement ... 14.6 liter (893 cu. in.)

Number and Arrangement of Cylinders ... 6, In Line

Firing Order (Injection Sequence) ... 1, 5, 3, 6, 2, 4

No. 1 Cylinder Location ... Front

Rotation of Crankshaft (when seen from flywheel end) ... counterclockwise

Rotation of Fuel Pump Camshaft (when seen from pump drive end) ... counterclockwise

Fuel System

3406B New Scroll Fuel System

Fuel Flow

Fuel System Schematic
(1) Fuel injection nozzle. (2) Fuel injection lines. (3) Fuel return line. (4) Constant bleed orifice (part of the elbow). (5) Fuel injection pump housing. (6) Fuel priming pump. (7) Check valves. (8) Fuel transfer pump. (9) Fuel tank. (10) Primary fuel filter. (11) Secondary fuel filter.

Fuel is pulled from fuel tank (9) through primary fuel filter (10) by fuel transfer pump (8). From the fuel transfer pump the fuel is pushed through secondary fuel filter (11) and to the fuel manifold in fuel injection pump housing (5). Fuel pressure in the fuel manifold is determined by the fuel transfer pump spring. A constant bleed orifice is in the fuel return line elbow. Constant bleed orifice (4) lets a constant flow of fuel go through fuel return line (3) back to fuel tank (9). This helps keep the fuel cool and free of air. The individual fuel injection pumps get fuel from the fuel manifold and push fuel at a very high pressure through fuel lines (2) to fuel injection nozzles (1). Each fuel injection nozzle has very small holes in the tip that change the flow of fuel to a very fine spray that gives good fuel combustion in the cylinder.

Fuel Injection Pump

The fuel injection pump increases the pressure of the fuel and sends an exact amount of fuel to the fuel injection nozzle. There is one fuel injection pump for each cylinder in the engine.

Fuel Injection Pump
(1) Spill port. (2) Check valve. (3) Pump barrel. (4) Bypass port. (5) Pump plunger. (6) Spring. (7) Fuel rack. (8) Gear. (9) Lifter. (10) Cam.

The fuel injection pump is moved by cam (10) of the fuel pump camshaft. When the camshaft turns, the cam raises lifter (9) and pump plunger (5). The pump plunger always makes a full stroke. As the camshaft turns farther, spring (6) returns the pump plunger and lifter to the bottom of the stroke.

Pump Barrel And Plunger Assembly
(1) Spill port. (2) Check valve. (3) Pump barrel. (4) Bypass port. (5) Pump plunger. (11) Orificed reverse flow check valve. (12) Spring. (13) Spring. (14) Scroll. (15) Slot.

When the pump plunger is at the bottom of the stroke, fuel at transfer pump pressure flows through spill port (1) and bypass port (4). Fuel fills pump barrel (3) in the area above pump plunger (5).

Pump Barrel And Plunger Assembly
(1) Spill port. (2) Check valve. (3) Pump barrel. (4) Bypass port. (5) Pump plunger. (11) Orificed reverse flow check valve. (12) Spring. (13) Spring. (14) Scroll. (15) Slot.

After pump plunger (5) begins the up stroke, fuel will be pushed out bypass port (4) until the top of the pump plunger closes the port. As the pump plunger travels farther up, the pressure of the fuel increases. At approximately 690 kPa (100 psi), check valve (2) opens and lets fuel flow into the fuel injection line to the fuel injection nozzle.

Pump Barrel And Plunger Assembly
(1) Spill port. (2) Check valve. (3) Pump barrel. (4) Bypass port. (5) Pump plunger. (11) Orificed reverse flow check valve. (12) Spring. (13) Spring. (14) Scroll. (15) Slot.

When the pump plunger travels farther up, scroll (14) uncovers spill port (1). The fuel above the pump plunger goes through slot (15), along the edge of scroll (14) and out spill port (1) back to the fuel manifold. This is the end of the injection stroke. The pump plunger can have more travel up, but no more fuel will be sent to the fuel injection nozzle.

Pump Barrel And Plunger Assembly
(1) Spill port. (2) Check valve. (4) Bypass port. (5) Pump plunger. (11) Orificed reverse flow check valve. (12) Spring. (13) Spring. (14) Scroll. (15) Slot.

When spill port (1) is opened by plunger (5) the fuel nozzle closes and spring (13) closes check valve (2) as the pressure above plunger (5) drops below 690 kPa (100 psi). At the same time orificed reverse flow check valve (11) opens.

Orificed reverse flow check valve (11) closes when the fuel pressure in the fuel injection lines is 6900 kPa (1000 psi). This keeps the fuel in the injection line and above the reverse flow check valve at 6900 kPa (1000 psi).

NOTE: Reverse flow check valve (11) prevents rough idle by stopping any secondary injection of fuel between injection strokes. This valve is only effective below 8250 kPa (1200 psi) and has no effect above that pressure. When the engine is shutdown, the pressure is gradually released through a small groove on the bottom face of reverse flow check valve (11).

When the pump plunger travels down and uncovers bypass port (4), fuel begins to fill the area above the pump plunger again, and the pump is ready to begin another stroke.

The amount of fuel the injection pump sends to the injection nozzle on each pump stroke can be changed by the rotation of the pump plunger. Gear (8) is attached to the pump plunger and is in mesh with fuel rack (7). The governor moves the fuel rack which turns the fuel pump plungers according to the fuel needs of the engine. When the governor turns the pump plunger, scroll (14) on the plunger changes the distance between the top of pump plunger and the point where scroll (14) uncovers spill port (1). The longer the distance from the top of the pump plunger to the point where scroll (14) uncovers spill port (1), the more fuel will be injected.

To stop the engine, the pump plunger is rotated so that slot (15) on the pump plunger is in line with spill port (1). The fuel will now go out the spill port and not to the injection nozzle.

Fuel Injection Nozzle

The fuel injection nozzle is installed in an adapter in the cylinder head and extended into the combustion chamber. The fuel injection pump sends fuel with high pressure to the fuel injection nozzle where the fuel is made into a fine spray for good combustion.

Fuel Injection Nozzle
(1) Carbon dam. (2) Seal. (3) Passage. (4) Filter screen. (5) Inlet passage. (6) Orifice. (7) Valve. (8) Diameter. (9) Spring.

Seal (2) goes against the nozzle adapter and prevents leakage of compression from the cylinder. Carbon dam (1) keeps carbon out of the bore of the nozzle adapter.

Fuel with high pressure from the fuel injection pump goes into inlet passage (5). Fuel then goes through screen (4) and into passage (3) to the area below diameter (8) of valve (7). When the pressure of the fuel that pushes against diameter (8) becomes greater than the force of spring (9), valve (7) lifts up. This occurs when the fuel pressure goes above the Valve Opening Pressure of the fuel injection nozzle. When valve (7) lifts, the tip of the valve comes off of the nozzle seat and the fuel will go through the six small orifices (6) into the combustion chamber.

The injection of fuel continues until the pressure of fuel against diameter (8) becomes less than the force of spring (9). With less pressure against diameter (8), spring (9) pushes valve (7) against the nozzle seat and stops the flow of fuel to the combustion chamber.

The fuel injection nozzle can not be disassembled and no adjustments can be made.

Fuel Transfer Pump

The fuel transfer pump is a piston pump that is moved by a cam (eccentric) on the camshaft for the fuel injection pump. The transfer pump is located on the bottom side of the fuel injection pump housing.

Fuel Transfer Pump (Start Of Down Stroke) (Arrows Indicate Fuel Flow Direction)
(1) Push rod. (2) Piston. (3) Outlet check valve. (4) Pumping check valve. (5) Pumping spring. (6) Pump inlet port. (7) Inlet check valve. (8) Pump outlet port.

When the fuel injection pump camshaft turns, the cam moves push rod (1) and piston (2) down. As the piston moves down, inlet check valve (7) and outlet check valve (3) close. Pumping check valve (4) opens and allows the fuel below the piston to move into the area above the piston. Pumping spring (5) is compressed as the piston is pushed down by push rod (1).

As the fuel injection pump camshaft continues to turn, the cam no longer puts force on push rod (1). Pumping spring (5) now moves piston (2) up. This causes pumping check valve (4) to close. Inlet check valve (7) and outlet check valve (3) will open. As the piston moves up, the fuel in the area above the piston is pushed through the outlet check valve (3) and out pump outlet port (8). Fuel also moves through pump inlet port (6) and inlet check valve (7) to fill the area below piston (2). The pump is now ready to start a new cycle.

Fuel Transfer Pump (Start Of Up Stroke) (Arrows Indicate Fuel Flow Direction)
(1) Push rod. (2) Piston. (3) Outlet check valve. (4) Pumping check valve. (5) Pumping spring. (6) Pump inlet port. (7) Inlet check valve. (8) Pump outlet port.

Oil Flow For Fuel Injection Pump And Governor

Fuel Injection Pump And Governor
(1) Servo. (2) Fuel injection pump housing. (3) Cover. (4) Oil supply from cylinder block. (5) Oil drain into cylinder block. (6) Dashpot. (7) Governor rear housing. (8) Governor center housing.

Lubrication oil from the side of the cylinder block goes into the side of the fuel injection pump housing at location (4). The oil then goes to a passage between fuel injection pump housing (2) and governor center housing (8) where it flows to three different locations.

A part of the oil goes back into the main oil passage in fuel injection pump housing (2). This oil gives a supply of lubrication for the three fuel injection pump camshaft bearings. At the camshaft bearing next to the governor, oil flows into drilled passages in the camshaft to give lubrication to the flyweight carrier thrust bearing. Oil drains from the camshaft bearings into the fuel injection pump housing. A drain hole in the housing keeps the level of oil in the housing even with the center of the camshaft. Oil drains from the housing, through drain port (5), back to the engine block.

Oil also flows through a different passage back to the fuel injection pump housing. This passage is connected to governor servo (1). The governor servo gives hydraulic assistance to move the fuel rack.

The remainder of the oil goes through a passage in the governor center housing (8) and governor rear housing (7) to cover (3) or the fuel ratio control. From the cover or the fuel ratio control, oil drains back into the governor housing. This oil lubricates the governor control components and supplies the oil for the dashpot (6). The internal parts of the governor are also lubricated by oil leakage from governor servo (1) and the oil thrown off by parts in rotation. An opening between the lower part of the governor and the fuel injection pump housing lets oil out of the governor. The fuel injection pump housing has an oil drain port (5) that is connected to the engine block.

Governor

Governor
(1) Governor spring. (2) Sleeve. (3) Valve. (4) Piston. (5) Governor servo. (6) Fuel rack. (7) Lever. (8) Flyweights. (9) Over fueling spring. (10) Load stop bar. (11) Stop bar. (12) Riser. (13) Spring seat. (14) Torque rise setting screw. (15) Stop bolt. (16) Torque spring. (17) Fuel setting screw. (18) Stop collar.

The governor controls the amount of fuel needed by the engine to maintain a desired rpm.

The governor flyweights (8) are driven directly by the fuel pump camshaft. Riser (12) is moved by flyweights (8) and governor spring (1). Lever (7) connects the riser with sleeve (2) which is fastened to valve (3). Valve (3) is a part of governor servo (5) and moves piston (4) and fuel rack (6). The fuel rack moves toward the front of the fuel pump housing (to the right in the illustration) when moved in the FUEL OFF direction.

The force of governor spring (1) always pushes to give more fuel to the engine. The centrifugal (rotating) force of flyweights (8) always push to get a reduction of fuel to the engine. When these two forces are in balance (equal), the engine runs at a constant rpm.

When the engine is cranked to start and the governor is at low idle position, over fueling spring (9) moves the riser forward and gives an extra amount of fuel to the engine. When the engine has started and begins to run, the flyweight force becomes greater than the force of the over fueling spring. The riser moves to the rear and reduces the amount of fuel to the low idle requirement of the engine.

When the governor control lever is moved to the high idle position, governor spring (1) is put in compression and pushes riser (12) toward the flyweights. When the riser moves forward, lever (7) moves sleeve (2) toward the rear. Sleeve (2) moves valve (3) through the broken link spring. Valve (3) stops oil flow through governor servo (5) and the oil pressure moves piston (4) and the fuel rack to the rear. This increases the amount of fuel to the engine. As engine speed increases, the flyweight force increases and moves the riser toward the governor spring. When the riser moves to the rear, lever (7) moves sleeve (2) and valve (3) forward. Valve (3) now directs oil pressure to the rear of piston (4) and moves the piston and fuel rack forward. This decreases the amount of fuel to the engine. When the flyweight force and the governor spring force become equal, the engine speed is constant and the engine runs at high idle rpm. High idle rpm is adjusted by the high idle adjustment screw. The adjustment screw limits the amount of compression of the governor spring.

With the engine at high idle, when the load is increased, engine speed will decrease. Flyweights (8) move in and governor spring (1) pushes riser (12) forward and increases the amount of fuel to the engine. As the load is increased more, governor spring (1) pushes riser (12) farther forward. Spring seat (13) also pushes on stop bolt (15). On the opposite end of stop bolt (15) is stop collar (18) which has fuel setting screw (17) and torque rise setting screw (14). Torque rise setting screw (14) controls the maximum amount of fuel rack travel. As stop bolt (15) moves forward fuel setting screw (17) moves forward to make full contact with torque spring (16) at the full load speed of the engine. The adjustment of fuel setting screw (17) controls the horsepower of the engine at full load speed. Torque spring (16) now acts to control the fuel rack movement.

If more load is added, the engine will run in a lug condition. This occurs when the load placed on the engine is greater than the horsepower output at the full load speed. When rpm decreases because of added load, the force of governor spring (1) moves riser (12) farther forward. As stop bolt (15) moves forward, fuel setting screw (17) bends torque spring (16) and fuel rack (6) can move farther in the FUEL ON direction.

This movement is stopped when torque rise setting screw (14) contacts stop bar (11). This is the maximum fuel setting position. The adjustment of torque rise setting screw (14) controls the additional amount of fuel rack travel below full load speed as the peak torque speed of the engine is reached.

Also, the engine can be shutdown if the mechanical action of governor spring (1) and flyweights (8) become bound (stuck) in the FUEL ON position. Shutdown can be done by use of the shutoff solenoid or by moving the manual shutoff lever (if so equipped) to the off position. Valve (3) will move independent of sleeve (2) to push fuel rack (6) to the FUEL OFF position. Note that the broken link spring is compressed as valve (3) slides in sleeve (2).

Governor Servo

The governor servo gives hydraulic assistance to the mechanical governor force to move the fuel rack. The governor servo has cylinder (3), cylinder sleeve (4), piston (2) and valve (1).

Governor Servo (Fuel on direction)
(1) Valve. (2) Piston. (3) Cylinder. (4) Cylinder sleeve. (5) Fuel rack. (A) Oil inlet. (B) Oil outlet. (C) Oil passage. (D) Oil passage.

When the governor moves in the FUEL ON direction, valve (1) moves to the left. The valve opens oil outlet (B) and closes oil passage (D). Pressure oil from oil inlet (A) pushes piston (2) and fuel rack (5) to the left. Oil behind the piston goes through oil passage (C), along valve (1) and out oil outlet (B).

Governor Servo (Balanced position)
(1) Valve. (2) Piston. (3) Cylinder. (4) Cylinder sleeve. (5) Fuel rack. (A) Oil inlet. (B) Oil outlet. (C) Oil passage. (D) Oil passage.

When the governor spring and flyweight forces are balanced and the engine speed is constant, valve (1) stops moving. Pressure oil from oil inlet (A) pushes piston (2) until oil passages (C and D) are opened. Oil now flows through oil passage (D) along valve (1) and out through oil outlet (B). With no oil pressure on the piston, the piston and fuel rack (5) stop moving.

Governor Servo (Fuel Off direction)
(1) Valve. (2) Piston. (3) Cylinder. (4) Cylinder sleeve. (5) Fuel rack. (A) Oil inlet. (B) Oil outlet. (C) Oil passage. (D) Oil passage.

When the governor moves in the FUEL OFF direction, valve (1) moves to the right. The valve closes oil outlet (B) and opens oil passage (D). Pressure oil from oil inlet (A) is now on both sides of piston (2). The area of the piston is greater on the left side than on the right side of the piston. The force of the oil is also greater on the left side of the piston and moves the piston and fuel rack (5) to the right.

Dashpot

Dashpot
(1) Needle valve. (2) Oil reservoir. (3) Cylinder. (4) Piston. (5) Dashpot spring. (6) Spring seat.

The dashpot helps give the governor better speed control when there are sudden speed and load changes. The dashpot has needle valve (1), oil reservoir (2), cylinder (3), piston (4), dashpot spring (5) and spring seat (6). Piston (4) and spring seat (6) are fastened to dashpot spring (5).

When spring seat (6) is moved, by a change in load or speed, dashpot spring (5) moves piston (4) in cylinder (3). The cylinder and oil reservoir (2) are full of oil. As piston (4) moves, it causes oil to be moved in or out of the cylinder through needle valve (1) and oil reservoir (2).

Needle valve (1) gives restriction to oil flow to and from cylinder (3). This causes a restriction to the movemnt of piston (4) and spring seat (6). The faster the governor tries to move spring seat (6), the greater the resistance the dashpot gives to the spring seat movement.

3406 Fuel System

Fuel System
(1) Injection valve. (2) Anti-siphon block. (3) Injection pump housing. (4) Priming pump. (5) Plug. (6) Secondary filter. (7) Fuel line. (8) Return line to tank. (9) Fuel tank. (10) Primary filter. (11) Transfer pump.

This engine has a pressure type fuel system. There is one injection pump and one injection valve for each cylinder. The injection pumps are in injection pump housing (3) on the left side of the engine. The injection valves are in the injection adapters, under the valve covers.

The transfer pump (11) pulls fuel from the fuel tank (9) through the primary filter (10) and sends it through the base of the priming pump (4) and the secondary filter (6), through the anti-siphon block (2) and to the manifold of the injection pump housing. When priming pump (4) is not used, the position of fuel line (7) and plug (5) are reversed.

Some of the fuel in the manifold is constantly sent back through anti-siphon block (2) and through return line (8) to the fuel tank to remove air from the system. Orifices in the anti-siphon block control the pressure in the fuel manifold and the amount of fuel that goes back to the fuel tank.

Fuel in the manifold of the injection pump housing is the supply for the injection pumps. The injection pumps are in time with the engine and send fuel to the injection valves under high pressure. When the fuel pressure at the injection valves is high enough the valve opens and sends fuel into the combustion chamber.

Transfer pump (11) has a bypass valve and a pressure relief valve. The bypass valve makes it possible for the priming pump to send fuel through the transfer pump. The pressure relief valve controls the maximum pressure of the fuel. When the pressure gets too high the valve opens and some of the fuel goes back to the inlet side of the pump.

When there is air on the inlet side of the fuel system the priming pump (4) is used. Operation of the priming pump fills the system with fuel. This forces the air back into the tank.

An automatic timing advance unit is mounted on the front of the engine and is connected to the drive shaft for the fuel injection pump.

It is driven by the engine camshaft gear inside the front timing gear housing. The automatic timing advance unit gives easier starting and smooth low speed operation. It will also advance timing as engine speed increases to give correct engine operating efficiency.

Fuel Injection Pump Operation

Cross Section Of The Housing For The Fuel Injection Pumps
(1) Fuel manifold. (2) Inlet passage in pump barrel. (3) Check valve. (4) Pump plunger. (5) Spring. (6) Gear. (7) Fuel rack. (8) Lifter. (9) Camshaft.

The rotation of the cams on the camshaft (9) cause lifters (8) and pump plungers (4) to move up and down. The stroke of each pump plunger is always the same. The force of springs (5) hold lifters (8) against the cams of the camshaft.

When the pump plunger is down, fuel from fuel manifold (1) goes through inlet passage (2) and fills the chamber above pump plunger (4). As the plunger moves up it closes the inlet passage.

The pressure of the fuel in the chamber above the plunger increases until it is high enough to cause check valve (3) to open. Fuel under high pressure flows out of the check valve through the fuel line to the injection valve, until the inlet passage is opened by the plunger. The pressure in the chamber decreases and check valve (3) closes.

The longer inlet passage (2) is closed, the larger the amount of fuel which will be forced through check valve (3). The period for which the inlet passage is closed is controlled by the design of the plunger. When the governor moves fuel rack (7), it moves gear (6) that is fastened to plunger (4). This causes rotation of the plungers and controls the period that inlet passage (2) is closed.

Fuel Injection Valves (Nozzles)

The fuel injection valves fit into injection adapters that are installed in the cylinder head.

Fuel, under high pressure from the injection pumps, is sent through the injection lines to the injection valves. The injection valves change the fuel to the correct fuel characteristic (spray pattern) for good combustion in the cylinders. The injection valves will not open until the fuel in the injection lines reaches a very high pressure. The valves then open quickly to release the fuel directly into the engine cylinder through six orifices in the tip of each nozzle.

Hydra-mechanical Governor With Dashpot

The governor controls the amount of fuel needed to keep a desired engine rpm over the complete engine speed range. The governor automatically makes up for variable engine loads to maintain a constant engine rpm.

When the engine is operating, the balance between the centrifugal force of governor weights and the force of the governor control on the governor spring, controls the movement of a valve and indirectly, the fuel rack. The valve directs pressure oil to either side of a rack positioning piston. Depending on the position of the valve, the rack is moved to increase and decrease the fuel to the engine to compensate for load variation.

Hydra-Mechanical Governor With Dashpot
(1) Cover for idle adjustment screws. (2) Collar bolt. (3) Dashpot chamber. (4) Dashpot piston. (5) Lever assembly. (6) Spring seat. (7) Governor weights. (8) Piston. (9) Cylinder. (10) Sleeve. (11) Oil passage. (12) Dashpot spring. (13) Governor spring. (14) Valve.

The governor has governor weights (7) driven by the engine through an accessory drive and the fuel injection pump camshaft. The governor has a governor spring (13), valve (14) and piston (8). The valve and piston are connected to the fuel rack.

The governor control is connected to the governor control lever and controls only the compression of governor spring (13). Compression of the spring always pushes to give more fuel to the engine. The centrifugal force (rotation) of governor weights (7) always pulls to get a reduction of fuel to the engine. When these two forces are in balance, the engine runs at the desired rpm (governed rpm).

The engine oil pump supplies engine oil under pressure to the governor through passages in the fuel injection pump housing. The oil under pressure goes to governor cylinder (9) through passage (11) around sleeve (10).

Governor In Increased Load Position
(7) Weights. (8) Piston. (9) Cylinder. (13) Governor spring. (14) Valve. (15) Oil drain passage for piston. (16) Upper oil passage in piston. (17) Low oil passage in piston. (18) Rack.

When the load on the engine increases, the engine rpm decreases and the rotation of governor weights (7) will get slower. The governor weights will move toward each other. Governor spring (13) moves valve (14) to open the oil passages in piston (8) and close oil drain passage (15). This lets the oil flow from passage (17), around valve (14), and through passage (16) to fill the chamber above piston (8). This pressure oil pushes piston (8) and rack (18) to give more fuel to the engine. Engine rpm increases until the rotation of the governor weights is fast enough to be in balance with the force of the governor spring.

Governor In Decreased Load Position
(7) Weights. (8) Piston. (9) Cylinder. (13) Governor spring. (14) Valve. (15) Oil drain passage for piston. (16) Upper oil passage in piston. (17) Low oil passage in piston. (18) Rack.

When there is a reduction in load on the engine, there will be an increase in engine rpm and the rotation of governor weights (7) will get faster. This will move valve (14). This stops oil flow from passage (17) and oil pressure above piston (8) goes out around valve (14) through the top of piston (8). Now, the pressure between sleeve (10) and piston (8) pushes the piston and rack (18). This causes a reduction in the amount of fuel to the engine. Engine rpm decreases until the centrifugal force (rotation) of the governor weights is in balance with the force of the governor spring. When these two forces are in balance, the engine will run at the desired rpm (governed rpm).

When the engine rpm is at LOW IDLE, a spring-loaded plunger in lever assembly (5) is in contact with a shoulder on the adjustment screw for low idle. To stop the engine, move the switch to the "OFF" position. This will cause the shutoff solenoid to move the spring-loaded plunger over the shoulder on the low idle adjustment screw and move the fuel rack to the fuel shutoff position. With no fuel to the engine cylinders, the engine will stop. To stop the engine manually, turn the shutoff lever on the governor housing to the shutoff position.

Oil from the engine gives lubrication to the governor weight bearing. The other parts of the governor get lubrication from "splash-lubrication" (oil thrown by other parts). Oil from the governor runs back into the housing for the fuel injection pumps.

Electric set engines need a governor that has better control over the engine speed range than a standard hydra-mechanical governor gives. A piston (4) and spring (12) around bolt (2), plus an oil reservoir (19), and two adjustment screws (21 and 22) are added to the basic hydra-mechanical governor. These parts control the flow of oil into and out of dashpot chamber (3) above piston (4), through internal oil passages. With correct oil flow into and out of dashpot chamber (3), lower spring seat (6) moves with more precision and the governor gives better control of the engine speed.

Top View Of Dashpot Governor
(1) Cover for idle adjustment screws. (2) Collar bolt. (19) Dashpot reservoir. (20) Governor control shaft. (21) Adjustment screw for dashpot. (22) Adjustment screw for supply oil to reservoir. (23) Governor shutoff shaft.

The oil for the dashpot action comes from the engine lubrication system. Adjustment screw (22) controls the oil flow from the lubrication system into reservoir (19), which has an overflow outlet back to the mechanical area of the governor. Too much oil flow to the reservoir will fill the governor with oil and decrease engine performance. Too little oil flow does not give enough oil to reservoir (19). Now the governor will hunt (increase and decrease engine speed constantly) as air gets into dashpot chamber (3) and lets piston (4) and lower spring seat (6) move faster.

Dashpot adjustment screw (21) causes a restriction to oil flow into and out of dashpot chamber (3). Too much oil flow lets lower spring seat (6) move faster, and the governor will hunt. Too little oil flow will cause slow governor action.

Automatic Timing Advance Unit

The automatic timing advance unit is installed on the front of the drive shaft (6) for the fuel injection pump and is gear driven through the timing gears. The drive gear (5) for the fuel injection pump is connected to the drive shaft for the fuel injection pump through a system of weights (2), springs (3), slides (4) and a flange (1). Two slides that are fastened to the flange fit into notches made on an angle in the weights. As centrifugal force (rotation) moves the weights outward against spring pressure, the movement of the notches in the weights causes the slides to make the flange turn through a small angle in relation to the gear. Since the flange is connected to the drive shaft for the fuel injection pump, the fuel injection timing is also changed. The unit advances the fuel injection pump camshaft 2 1/4° between approximately low idle and 1100 rpm. No adjustment can be made to these automatic timing advance units.

Automatic Timing Advance Unit
(1) Flange. (2) Weight. (3) Springs. (4) Slide. (5) Drive gear. (6) Drive shaft.

Woodward PSG Governors

Schematic Of PSG Governor
(1) Return spring. (2) Output shaft. (3) Output shaft lever. (4) Strut assembly. (5) Speeder spring. (6) Power piston. (7) Flyweights. (8) Needle valve. (9) Thrust bearing. (10) Pilot valve compensating land. (11) Buffer piston. (12) Pilot valve. (13) Pilot valve bushing. (14) Control ports. (A) Chamber. (B) Chamber.

Introduction

The Woodward PSG (Pressure Compensated Simple Governor) can operate as an isochronous or a speed droop type governor. It uses engine lubrication oil, increased to a pressure of 1200 kPa (175 psi) by a gear type pump inside the governor, to give hydramechanical speed control.

Pilot Valve Operation

The fuel injection pump camshaft drives a governor drive unit. This unit turns pilot valve bushing (13) clockwise as seen from the drive unit end of the governor. The pilot valve bushing is connected to a spring driven ballhead. Flyweights (7) are fastened to the ballhead by pivot pins. The centrifugal force caused by the rotation of the pilot valve bushing causes the flyweights to pivot out. This action of the flyweights changes the centrifugal force to axial force against speeder spring (5). There is a thrust bearing (9) between the toes of the flyweights and the seat for the speeder spring. Pilot valve (12) is fastened to the seat for the speeder spring. Movement of the pilot valve is controlled by the action of the flyweights against the force of the speeder spring.

The engine is at the governed (desired) rpm when the axial force of the flyweights is the same as the force of compression in the speeder spring. The flyweights will be in the position shown. Control ports (14) will be closed by the pilot valve.

Fuel Increase

When the force of compression in the speeder spring increases (operator increases desired rpm) or the axial force of the flyweights decreases (load on the engine increases) the pilot valve will move in the direction of the drive unit. This opens control ports (14). Pressure oil flows through a passage in the base to chamber (B). The increased pressure in chamber (B) causes power piston (6) to move. The power piston pushes strut assembly (4), that is connected to output shaft lever (3). The action of the output shaft lever causes counterclockwise rotation of output shaft (2). This moves fuel control linkage (15) in the FUEL ON direction.

PSG Governor Installed (Typical Illustration)
(2) Output shaft. (15) Fuel control linkage.

As the power piston moves in the direction of return spring (1) the volume of chamber (A) increases. The pressure in chamber (A) decreases. This pulls the oil from the chamber inside the power piston, above buffer piston (11) into chamber (A). As the oil moves out from above buffer piston (11) to fill chamber (A) the buffer piston moves up in the bore of the power piston. Chambers (A and B) are connected respectively to the chambers above and below the pilot valve compensating land (10). The pressure difference felt by the pilot valve compensating land adds to the axial force of the flyweights to move the pilot valve up and close the control ports. When the flow of pressure oil to chamber (B) stops so does the movement of the fuel control linkage.

Fuel Decrease

When the force of compression in the speeder spring decreases (operator decreases desired rpm) or the axial force of the flyweights increases (load on the engine decreases) the pilot valve will move in the direction of speeder spring (5). This opens control ports (14). Oil from chamber (B) and pressure oil from the pump will dump through the end of the pilot valve bushing. The decreased pressure in chamber (B) will let the power piston move in the direction of the drive unit. Return spring (1) pushes against strut assembly (4). This moves output shaft lever (3). The action of the output shaft lever causes clockwise rotation of output shaft (2). This moves fuel control linkage (15) in the FUEL OFF direction.

Earlier PSG Governor
(6) Power piston. (8) Needle valve. (10) Pilot valve compensating land. (11). Buffer piston. (14) Control ports. (A) Chamber. (B) Chamber.

As power piston (6) moves in the direction of the drive unit the volume of chamber (A) decreases. This pushes the oil in chamber (A) into the chamber above buffer piston (11). As the oil from chamber (A) flows into the power piston, it moves the buffer piston down in the bore of the power piston. The pressure at chamber (A) is more than the pressure at chamber (B). Chambers (A and B) are connected respectively to chambers above and below the pilot valve compensating land (10). The pressure difference felt by the pilot valve compensating land adds to the force of the speeder spring to move the pilot valve down and close the control ports. When the flow of oil from chamber (B) stops so does the movement of the fuel control linkage.

Hunting

There is a moment between the time the fuel control linkage stops its movement and the time the engine actually stops its increase or decrease of rpm. During this moment there is a change in two forces on the pilot valve, the pressure difference at the pilot valve compensating land and the axial force of the flyweights.

The axial force of the flyweights changes until the engine stops its increase or decrease of rpm. The pressure difference at the pilot valve compensating land changes until the buffer piston returns to its original position. A needle valve (8) in a passage between space (A) and (B) controls the rate at which the pressure difference changes. The pressure difference makes compensation for the axial force of the flyweights until the engine stops its increase or decrease of rpm. If the force on the pilot valve compensating land plus the axial force of the flyweights is not equal to the force of the speeder spring, the pilot valve will move. This movement is known as hunting (movement of the pilot valve that is not the result of a change in load or desired rpm of the engine).

PSG Governor Installed (Typical Illustration)
(8) Needle valve.

The governor will hunt each time the engine actually stops its increase or decrease of rpm at any other rpm than that desired. The governor will hunt more after a rapid or large change of load or desired rpm than after a gradual or small change.

Speed Adjustment

Later PSG governors use a clutch assembly (2) driven by a 110V AC/DC or 24V DC reversible synchronizing motor (1) to move link assembly (3) up or down. The clutch assembly protects the motor if the adjustment is run against the stops. The motor is controlled by a switch that is remotely mounted. The clutch assembly can be turned manually if necessary.

PSG Governor
(1) Synchronizing motor. (2) Clutch assembly. (3) Link assembly.

Speed Droop

PSG Governor
(1) Bracket. (2) Pivot pin. (3) Output shafts.

Speed droop is the difference between no load rpm and full load rpm. This difference in rpm divided by the full load rpm and multiplied by 100 is the percent of speed droop.

The speed droop of the PSG governor can be adjusted by movement of an adjustment lever on the outside of the governor that is connected to pivot pin (2) by link (4). The governor is isochronous when it is adjusted so that the no load and full load rpm is the same. Speed droop permits load division between two or more engines that drive generators connected in parallel or generators connected to a single shaft.

PSG Governor
(2) Pivot pin. (4) Link.

Speed droop adjustment on PSG governors is made by movement of pivot pin (2). When the pivot pin is put in alignment with the output shafts, movement of the output shaft lever will not change the force of the speeder spring. When the force of the speeder spring is kept constant the desired rpm will be kept constant. See PILOT VALVE OPERATION. When the pivot pin is moved out of alignment with the output shafts, movement of the output shaft lever will change the force of the speeder spring proportional to the load on the engine. When the force of the speeder spring is changed the desired rpm of the engine will change.

Air Inlet And Exhaust System

Air Inlet And Exhaust System
(1) Exhaust manifold. (2) Inlet manifold. (3) Engine cylinder. (4) Turbocharger compressor wheel. (5) Turbocharger turbine wheel. (6) Air inlet. (7) Exhaust outlet.

Air Inlet And Exhaust System
(1) Exhaust manifold. (8). Turbocharger.

The components of the air inlet and exhaust system control the quality and amount of air available for combustion. The air inlet and exhaust system components are: air cleaner, inlet manifold, cylinder head, valves and valve system components, exhaust manifold, and turbocharger.

Clean inlet air from the air cleaner is pulled through air inlet (6) by compressor wheel (4). The rotation of the compressor wheel causes compression of the air and forces it through inlet manifold (2) to the intake valves in the engine cylinder head. The intake valves control the air flow into each engine cylinder.

There are two intake and two exhaust valves for each cylinder. Make reference to Valve System Components. The intake valves open when the piston moves down on the inlet stroke. Cooled compressed air from the inlet manifold is pulled into the cylinder. The intake valves close and the piston starts to move up on the compression stroke. When the piston is near the top of the compression stroke fuel is injected into the cylinder.

The fuel mixes with the air and combustion starts. The force of combustion pushes the piston down on the power stroke. When the piston moves up again it is on the exhaust stroke. The exhaust valves open and the exhaust gases are pushed through the exhaust port into exhaust manifold (1). After the piston makes the exhaust stroke the exhaust valves close and the cycle (inlet, compression, power, exhaust) starts again.

Exhaust gases from the exhaust manifold go into the turbine side of the turbocharger (8) and cause turbine wheel (5) to turn. The turbine wheel is connected to the shaft that drives compressor wheel (4). The exhaust gases then go out the exhaust outlet (7) and through exhaust system.

Aftercooler

Some engines have an aftercooler installed in place of the inlet manifold.

Air Inlet System
(1) Aftercooler housing.

The aftercooler has a coolant charged core assembly. Coolant from the water pump flows through the front bonnet on the oil cooler to the aftercooler. It then flows through the core assembly and out of the aftercooler through a different pipe into the rear of the cylinder block.

Inlet air from the compressor side of the turbochargers flows into the aftercooler through a pipe. The air passes through the core assembly which lowers the temperature as much as 38 to 93°C (100 to 200°F). The cooler air goes out the bottom of the aftercooler into the air chamber then through the inlet ports (passages) in the cylinder heads.

Turbocharger

The turbocharger (3) is installed on the center section or at the rear of the exhaust manifold (2). All the exhaust gases from the engine go through the turbine side of the turbocharger. The compressor side of the turbocharger is connected to the inlet manifold or an aftercooler (if so equipped).

The exhaust gases go into turbine housing (12) and push the blades of turbine wheel (6). This causes the turbine wheel and compressor wheel to turn at up to 70,000 rpm.

Turbocharger
(1) Inlet manifold. (2) Exhaust manifold. (3) Turbocharger.

Turbocharger (Typical Example)
(4) Air inlet. (5) Compressor wheel. (6) Turbine wheel. (7) Exhaust outlet. (8) Compressor housing. (9) Thrust bearing. (10) Sleeve. (11) Lubrication inlet port. (12) Turbine housing. (13) Sleeve. (14) Sleeve. (15) Oil deflector. (16) Bearing. (17) Oil outlet port. (18) Bearing. (19) Exhaust inlet. (20) Air outlet.

Clean air from the air cleaners is pulled through the compressor housing air inlet (4) by rotation of compressor wheel (5). The action of the compressor wheel blades causes a compression of the inlet air. This compression gives the engine more power because it makes it possible for the engine to burn additional fuel with greater efficiency.

Maximum rpm of the turbocharger is controlled by the fuel setting, the set point rpm and the height above sea level at which the engine is operated.

The bearings (16 and 18) in the turbocharger use engine oil under pressure for lubrication. The oil comes in through oil inlet port (11) and goes through passages in the center section for lubrication of the bearings. Then the oil goes out oil outlet port (17) and back to the engine lubrication system.

Valves And Valve System Components

The valves and valve system components control the flow of inlet air and exhaust gases into and out of the cylinder during engine operation.

Valve System Components
(1) Intake bridge. (2) Intake rocker arm. (3) Push rod. (4) Rotocoil. (5) Valve spring. (6) Valve guide. (7) Intake valves. (8) Lifter. (9) Camshaft.

The intake and exhaust valves are opened and closed by movement of these components: crankshaft, camshaft, lifters, push rods, rocker arms, bridges, and valve springs. Rotation of the crankshaft causes rotation of the camshaft. The camshaft gear is timed to, and driven by, a gear on the front of the crankshaft. As camshaft (9) turns, the lobes of the camshaft also turn and cause lifters (8) to go up and down. This movement makes push rods (3) move rocker arms (2). Movement of the rocker arms will make intake and exhaust bridges (1 and 11) move up and down on dowels mounted in the cylinder head.

These bridges let one rocker arm operate two valves (intake or exhaust) for each cylinder. There are two intake and two exhaust valves in each cylinder. Movement of the bridges will make the intake and exhaust valves in the cylinder head open and close according to the firing order (injection sequence) of the engine. One valve spring (5) for each valve holds the valves in the closed position.

Valve System Components
(1) Intake bridge. (2) Intake rocker arm. (7) Intake valves. (10) Exhaust rocker arm. (11) Exhaust bridge. (12) Exhaust valves.

Rotocoil assemblies (4) cause the valves to have rotation while the engine is running. This rotation of the valves keeps the deposit of carbon on the valves to a minimum and gives the valves longer service life.

Lubrication System

Lubrication System Components
(1) Oil return line from turbocharger. (2) Oil supply line to turbocharger. (3) Oil cooler. (4) Oil manifold in cylinder block. (5) Oil filter. (6) Oil pan.

The lubrication system has the following components: oil pan, oil pump, oil cooler, oil filter, oil lines to and from the turbocharger and oil passages in the cylinder block.

Oil Flow Through The Oil Filter And Oil Cooler

With the engine warm (normal operation), oil comes from the oil pan (6) through the suction bell (9) to the oil pump (7). The oil pump sends warm oil to the oil cooler (10) and then to the oil filter (4). From the oil filter, oil is sent to the oil manifold (1) in the cylinder block and to the oil supply line (2) for the turbocharger. Oil from the turbocharger goes back through the oil return line (3) to the oil pan.

With the engine cold (starting conditions), oil comes from the oil pan (6) through the suction bell (9) to the oil pump (7). When the oil is cold, an oil pressure difference in bypass valves (5 and 8) will cause the bypass valves to open. These bypass valves give immediate lubrication to all components when cold oil with high viscosity causes a restriction to the oil flow through the oil cooler (10) and oil filter (4). The oil pump then sends the cold oil through the bypass valve (8) for the oil cooler and through the bypass valve (5) for the oil filter, to the oil manifold (1) in the cylinder block and to the supply line (2) for the turbocharger. Oil from the turbocharger goes back through the oil return line (3) to the oil pan.

When the oil gets warm, the pressure difference in the bypass valves decrease and the bypass valves close. Now there is a normal oil flow through the oil cooler and oil filter.

Flow Of Oil (Engine Warm)
(1) Oil manifold in cylinder block. (2) Oil supply line to turbocharger. (3) Oil return line from turbocharger. (4) Oil filter. (5) Bypass valve for the oil filter. (6) Oil pan. (7) Oil pump. (8) Bypass valve for the oil cooler. (9) Suction bell. (10) Oil cooler.

Flow Of Oil (Engine Cold)
(1) Oil manifold in cylinder block. (2) Oil supply line to turbocharger. (3) Oil return line from turbocharger. (4) Oil filter. (5) Bypass valve for the oil filter. (6) Oil pan. (7) Oil pump. (8) Bypass valve for the oil cooler. (9) Suction bell. (10) Oil cooler.

The bypass valves will also open when there is a restriction in the oil cooler or oil filter. This action does not let an oil cooler or oil filter with a restriction prevent the lubrication of the engine.

Oil Flow In The Engine

Oil Flow In The Engine
(1) Bracket for the rocker arm shaft. (2) Rocker arm shaft. (3) Oil passage to the fuel injection pump and governor. (4) Valve lifter bore. (5) Oil passage to turbocharger. (6) Oil passage to cylinder head. (7) Oil passage to idler gear and gear housing. (8) Oil passage to valve lifters. (9) Oil jet tubes. (10) Camshaft bearing bores. (11) Oil manifold. (12) Main bearing bores. (13) Oil cooler. (14) Oil pump. (15) Oil passage to oil cooler. (16) Oil filter.

From the oil manifold (11) in the cylinder block, oil is sent through drilled passages in the cylinder block that connect the main bearings (12) and the camshaft bearings (10). Oil goes through drilled holes in the crankshaft to give lubrication to the connecting rod bearings. A small amount of oil is sent through oil jet tubes (9) to make the pistons cooler. Oil goes through grooves in the bores for the front and rear camshaft bearings and then into passages (8) that connects the valve lifter bores (4). These passages give oil under pressure for the lubrication of the valve lifters.

Oil is sent through passages (6) to the mounting hole for brackets (1) for the rocker arm shaft. Then oil goes up the mounting holes for the front and rear brackets for the rocker arm shaft and into the rocker arm shafts (2). Holes in the rocker arm shafts lets the oil give lubrication to the valve system components in the cylinder head.

The idler gear and accessory drive gets oil from passage (7) in the cylinder block through a passage in the shaft for the idler gear installed on the front of the cylinder block.

The fuel injection pump and governor gets oil from passage (3) in the cylinder block. The automatic timing advance unit gets oil from the fuel injection pump through the drive shaft for the fuel injection pump. The 3406B does not have an automatic timing advance.

There is a pressure control valve in the oil pump. This valve controls the pressure of the oil coming from the oil pump. The oil pump can put more oil into the system than is needed. When there is more oil than needed, the oil pressure goes up and the valve will open. This allows the oil that is not needed to go back to the inlet oil passage of the oil pump.

After the lubricating oil has done its work, it goes back to the engine oil pan.

Cooling System

This engine has a pressure type cooling system. A pressure type cooling system gives two advantages. The first advantage is that the cooling system can have safe operation at a temperature that is higher than the normal boiling (steam) point of water. The second advantage is that this type system prevents cavitation (the sudden making of low pressure bubbles in liquids by mechanical forces) in the water pump. With this type system, it is more difficult for an air or steam pocket to be made in the cooling system.

Radiator Cooled System

Radiator Cooled System (Engine Warm)
(1) Aftercooler. (2) Water temperature regulator. (3) Outlet hose. (4) Radiator cap. (5) Cylinder head. (6) Tube to aftercooler. (7) Elbow from aftercooler. (8) Water elbow. (9) Water pump. (10) Radiator. (11) Cylinder block. (12) Oil cooler. (13) Inlet hose.

In normal operation (engine warm) the water pump (9) sends coolant through the oil cooler (12) and into the cylinder block (11). Coolant moves through the cylinder block into the cylinder head (5) and then goes to the housing for the temperature regulator (2). The temperature regulator is open and the coolant goes through the outlet hose (3) to the radiator (10). The coolant is made cooler as it moves through the radiator. When the coolant gets to the bottom of the radiator, it goes through the inlet hose (13) and into the water pump.

When the engine is cold, the water temperature regulator (2) is closed, and the coolant is stopped from going to the radiator. The coolant goes from the housing for the temperature regulator back to the water pump (9) through water elbow (8).

NOTE: The water temperature regulator (2) is an important part of the cooling system. If the water temperature regulator is not installed in the system, the coolant will not go through the radiator and overheating (engine runs too hot) will be the result.

On an engine with an aftercooler, a small amount of coolant comes out of the bonnet for the oil cooler and goes through tube (6) to the aftercooler (1). This coolant goes through the aftercooler and out elbow (7) and back into the cylinder block.

Keel Cooled System

Keel Cooled System (Engine Warm)
(1) Water cooled turbocharger. (2) Tube. (3) Elbow. (4) Aftercooler. (5) Water cooled exhaust manifold. (6) Cylinder head. (7) Outlet pipe. (8) Pipe. (9) Temperature regulator housing. (10) Pressure cap. (11) Expansion tank. (12) Tube. (13) Water pump. (14) Elbow. (15) Tube. (16) Inlet line. (17) Tube. (18) Outlet line. (19) Cylinder block. (20) Engine oil cooler. (21) Keel cooler.

In normal operation (engine warm) water pump (13) sends coolant through engine oil cooler (20) into cylinder block (19). Coolant moves through the cylinder block into cylinder head (6) and then goes through outlet pipe (7) and into outlet line (18). The coolant then goes through the outlet line to keel cooler (21) where the coolant is made cooler. From the keel cooler, the coolant goes through inlet line (16) through temperature regulator housing (9) and into expansion tank (11). The coolant from the expansion tank goes through tube (15) and back into the water pump.

When the engine is cold, water temperature regulator (9) lets the coolant from cylinder head (6) go through pipe (8) and into expansion tank (11). From the expansion tank, the coolant goes through tube (15) and back into the water pump. The coolant is not sent through the keel cooler until the engine is warm.

NOTE: Water temperature regulator (9) is an important part of the cooling system. If the water temperature regulator is not installed in the system, the coolant will not go through the keel cooler and overheating (engine runs too hot) will be the result.

Pressure cap (10) is used to keep the correct pressure in the cooling system. This pressure keeps a constant supply of coolant to the water pump. If this pressure goes too high, a valve in the pressure cap moves (opens) to get a reduction of pressure. When the correct pressure is in the cooling system, the valve in the pressure cap moves down (to the closed position).

On an engine with an aftercooler, a small amount of coolant comes out of the bonnet for the oil cooler and goes through tube (12) to aftercooler (4). This coolant goes through the aftercooler and out elbow (14) and back into the cylinder block.

Some engines are equipped with a water cooled exhaust manifold (5) and a water cooled turbocharger (1). The coolant for the exhaust manifold comes from the back of cylinder head (6) through elbow (3) and goes out of the manifold through outlet pipe (7). The coolant for the turbocharger comes from the bonnet for engine oil cooler (20) through tube (17) to the turbocharger. The coolant goes out of the turbocharger through tube (2) and into the water cooled exhaust manifold.

Heat Exchanger Cooled System

Heat Exchanger Cooled System (Engine Warm)
(1) Water cooled turbocharger. (2) Tube. (3) Elbow. (4) Water cooled exhaust manifold. (5) Cylinder head. (6) Outlet pipe. (7) Pipe. (8) Outlet line. (9) Temperature regulator housing. (10) Pressure cap. (11) Expansion tank. (12) Inlet pipe. (13) Water pump. (14) Tube. (15) Heat exchanger. (16) Cylinder block. (17) Engine oil cooler. (18) Tube. (19) Pump.

In normal operation (engine warm) water pump (13) sends coolant through engine oil cooler (17) and into cylinder block (16). Coolant moves through the cylinder block into cylinder head (5) and then goes through outlet pipe (6) and into outlet line (8). The coolant then goes through the outlet line to heat exchanger (15) where the coolant is made cooler. From the heat exchanger, the coolant goes through inlet line (12) through temperature regulator housing (9) and into expansion tank (11). The coolant from the expansion tank goes through tube (19) and back into the water pump.

When the engine is cold, water temperature regulator (9) lets the coolant from cylinder head (5) go through pipe (7) and into expansion tank (11). From the expansion tank, the coolant goes through tube (18) and back into water pump (13). The coolant is not sent through the heat exchanger until the engine is warm.

NOTE: Water temperature regulator (9) is an important part of the cooling system. If the water temperature regulator is not installed in the system, the coolant will not go through the heat exchanger and overheating (engine runs too hot) will be the result.

Pressure cap (10) is used to keep the correct pressure in the cooling system. This pressure keeps a constant supply of coolant to the water pump. If this pressure goes too high, a valve in the pressure cap moves (opens) to get a reduction of pressure. When the correct pressure is in the cooling system, the valve in the pressure cap moves down (to the closed position).

Water from an external source is sent through heat exchanger (15) by pump (19). This water makes the heat exchanger cooler.

Some engines are equipped with a water cooled exhaust manifold (4) and a water cooled turbocharger (1). The coolant for the exhaust manifold comes from the back of cylinder head (5) through elbow (3) and goes out of the manifold through outlet pipe (6). The coolant for the turbocharger comes from the bonnet for engine oil cooler (17) through tube (14) to the turbocharger. The coolant goes out of the turbocharger through tube (2) and into the water cooled exhaust manifold.

Coolant Conditioner (An Attachment)

Cooling System With Coolant Conditioner
(1) Cylinder liner. (2) Coolant bypass line. (3) Coolant outlet (to radiator). (4) Radiator. (5) Temperature regulator. (6) Water pump. (7) Coolant conditioner element. (8) Engine oil cooler. (9) Coolant inlet (from radiator).

Some conditions of operation have been found to cause pitting (small holes in the metal surface) from corrosion or cavitation erosion (wear caused by air bubbles in the coolant) on the outer surface of the cylinder liners and the inner surface of the cylinder block next to the liners. The addition of a corrosion inhibitor (a chemical that gives a reduction of pitting) can keep this type of damage to a minimum.

The "spin-on" coolant conditioner elements, similar to the fuel filter and oil filter elements, fasten to a base that is mounted on the engine or is remote mounted. Coolant flows through lines from the water pump to the base and back to the block or to the air compressor (if so equipped). There is a constant flow of coolant through the element.

The element has a specific amount of inhibitor for acceptable cooling system protection. As coolant flows through the element, the corrosion inhibitor, which is a dry material, dissolves (goes into solution) and mixes to the correct concentration. Two basic types of elements are used for the cooling system, and they are called the "PRECHARGE" and the "MAINTENANCE" elements. Each type of element has a specific use and must be used correctly to get the necessary concentration for cooling system protection.

The "PRECHARGE" element has more than the normal amount of inhibitor, and is used when a system is first filled with new coolant (unless Dowtherm 209 Antifreeze is used). This element has to add enough inhibitor to bring the complete cooling system up to the correct concentration.

The "MAINTENANCE" elements have a normal amount of inhibitor and are installed at the first change interval and provide enough inhibitor to keep the corrosion protection at an acceptable level. After the first change period, only "MAINTENANCE" elements are installed at specified intervals to give protection to the cooling system.

Basic Block

Vibration Damper

The twisting of the crankshaft, due to the regular power impacts along its length, is called twisting (torsional) vibration. The vibration damper is installed on the front end of the crankshaft. It is used for reduction of torsional vibrations and stops the vibration from building up to amounts that cause damage.

Vibration Damper
(1) Flywheel ring. (2) Rubber ring. (3) Inner hub.

The damper is made of a flywheel ring (1) connected to an inner hub (3) by a rubber ring (2). The rubber makes a flexible coupling between the flywheel ring and the inner hub.

Crankshaft

The crankshaft changes the combustion forces in the cylinder into usable rotating torque which powers the machine. There is a gear at the front of the crankshaft to drive the timing gears and the oil pump.

The crankshaft is supported by seven main bearings. Pressure oil is supplied to all bearing surfaces through drilled holes in the crankshaft.

Lip seals and wear sleeves are used at both ends of the crankshaft for easy replacement and a reduction of maintenance cost.

The 3406B has special design seals and wear sleeves at both ends of the crankshaft. The seal for the front is different than the seal for the rear. SPECIAL INSTRUCTION Form No. SMHS8008 gives the procedure that must be used to install these seals.

Camshaft

This engine uses a single, forged camshaft that is driven at the front end and is supported by seven bearings. Each lobe on the camshaft moves a roller follower, which in turn moves a push rod and two valves (either exhaust or intake) for each cylinder.

Cylinder Block And Liners

A steel spacer plate is used between the cylinder heads and the block to eliminate liner counterbore and to provide maximum liner flange support area (the liner flange sits directly on the cylinder block).

Engine coolant flows around the liners to cool them. Three O-ring seals at the bottom and a filler band at the top of each cylinder liner form a seal between the liner and the cylinder block.

Pistons, Rings And Connecting Rods

The cast aluminum piston has three rings; two compression rings and one oil ring. All rings are located above the piston pin bore. The two compression rings are of the KEYSTONE type and seat in an iron band that is cast into the piston. KEYSTONE rings have a tapered shape and the movement of the rings in the piston groove (also of tapered shape) results in a constantly changing clearance (scrubbing action) between the ring and the groove. This action results in a reduction of carbon deposit and possible sticking of rings.

The oil ring is a standard (conventional) type and is spring loaded. Holes in the oil ring groove provide for the return of oil to the crankcase.

The piston has a full skirt and uses a special shape (cardioid design) of the top surface to help combustion efficiency.

The full floating piston pin is retained by two snap rings which fit in grooves in the pin bore.

Oil spray tubes, located on the cylinder block main webs, direct oil to cool and lubricate the piston components and cylinder walls.

Electrical System

The electrical system has three separate circuits; the charging circuit, the starting circuit and the low amperage circuit. Some of the electrical system components are used in more than one circuit. The battery (batteries), circuit breaker, ammeter, cables and wires from the battery are all common in each of the circuits.

The charging circuit is in operation when the engine is running. An alternator makes electricity for the charging circuit. A voltage regulator in the circuit controls the electrical output to keep the battery at full charge.

If the machine has a disconnect switch, the starting circuit can operate only after the disconnect switch is put in the ON position.

The starting circuit is in operation only when the start switch is activated.

The low amperage circuit and the charging circuit are both connected to the same side of the ammeter. The starting circuit connects to the opposite side of the ammeter.

Charging System Components

Alternator (Delco-Remy)

The alternator is driven by V-belts from the crankshaft pulley. This alternator is a three phase, self-rectifying charging unit, and the regulator is part of the alternator.

This alternator design has no need for slip rings or brushes, and the only part that has movement is the rotor assembly. All conductors that carry current are stationary. The conductors are: the field winding, stator windings, six rectifying diodes and the regulator circuit components.

The rotor assembly has many magnetic poles like fingers with air space between each opposite pole. The poles have residual magnetism (like permanent magnets) that produce a small amount of magnet-like lines of force (magnetic field) between the poles. As the rotor assembly begins to turn between the field winding and the stator windings, a small amount of alternating current (AC) is produced in the stator windings from the small magnetic lines of force made by the residual magnetism of the poles. This AC current is changed to direct current (DC) when it passes through the diodes of the rectifier bridge. Most of this current goes to charge the battery and to supply the low amperage circuit, and the remainder is sent on to the field windings. The DC current flow through the field windings (wires around an iron core) now increases the strength of the magnetic lines of force. These stronger lines of force now increase the amount of AC current produced in the stator windings. The increased speed of the rotor assembly also increases the current and voltage output of the alternator.

The voltage regulator is a solid state (transistor, stationary parts) electronic switch. It feels the voltage in the system and switches on and off many times a second to control the field current (DC current to the field windings) for the alternator to make the needed voltage output.

Delco-Remy Alternator
(1) Regulator. (2) Roller bearing. (3) Stator winding. (4) Ball bearing. (5) Rectifier bridge. (6) Field winding. (7) Rotor assembly. (8) Fan.

Alternator (Bosch)

The alternator is driven by V-belts from the crankshaft pulley. This alternator is a three phase, self-rectifying charging unit, and the regulator is part of the alternator.

Bosch Alternator
(1) Fan. (2) Stator winding. (3) Field winding. (4) Regulator. (5) Ball bearing. (6) Roller bearing. (7) Rotor. (8) Rectifier assembly.

This alternator design has no need for slip rings or brushes, and the only part that has movement is the rotor assembly. All conductors that carry current are stationary. The conductors are: the field winding, stator windings, six rectifying diodes, and the regulator circuit components.

The rotor assembly has many magnetic poles like fingers with air space between each opposite pole. The poles have residual magnetism (like permanent magnets) that produce a small amount of magnet-like lines of force (magnetic field) between the poles. As the rotor assembly begins to turn between the field winding and the stator windings, a small amount of alternating current (AC) is produced in the stator windings from the small magnetic lines of force made by the residual magnetism of the poles. This AC current is changed to direct current (DC) when it passes through the diodes of the rectifier bridge. Most of this current goes to charge the battery and to supply the low amperage circuit, and the remainder is sent to the field windings. The DC current flow through the field windings (wires around an iron core) now increases the strength of the magnetic lines of force. These stronger lines of force now increase the amount of AC current produced in the stator windings. The increased speed of the rotor assembly also increases the current and voltage output of the alternator.

The voltage regulator is a solid state (transistor, stationary parts) electronic switch. It feels the voltage in the system and switches on and off many times a second to control the field current (DC current to the field windings) for the alternator to make the needed voltage output.

Alternator (Motorola)

The alternator is a three phase, self-rectifying charging unit that is driven by V-belts. The only part of the alternator that has movement is the rotor assembly. Rotor assembly (4) is held in position by a ball bearing at each end of the rotor shaft.

The alternator is made up of a front frame at the drive end, rotor assembly (4), stator assembly (3), rectifier assembly, brushes and holder assembly (5), slip rings (1) and rear end frame. Fan (2) provides heat removal by the movement of air through the alternator.

Rotor assembly (4) has field windings (wires around an iron core) that make magnetic lines of force when direct current (DC) flows through them. As the rotor assembly turns, the magnetic lines of force are broken by stator assembly (3). This makes alternating current (AC) in the stator. The rectifier assembly diodes that change the alternating current (AC) from the stator to direct current (DC). Most of the DC current goes to charge the battery and make a supply for the low amperage circuit. The remainder of the DC current is sent to the field windings through the brushes.

Motorola Alternator
(1) Slip rings. (2) Fan. (3) Stator assembly. (4) Rotor assembly. (5) Brush and holder assembly.

Alternator (Nippondenso)

The alternator is driven by V-belts from the crankshaft pulley. There is a 35 amp and a 50 amp, 24 volt alternator available. The alternators are brushless and contain an internally mounted, solid state voltage regulator.

Nippondenso Alternator Components
(1) Fan. (2) Front frame assembly. (3) Stator assembly. (4) Rotor assembly. (5) Field winding (coil) assembly. (6) Regulator assembly. (7) Condenser (suppression capacitor). (8) Rectifier assembly. (9) Rear frame assembly.

The major components of the alternator are stator assembly (3), rectifier assembly (8), field winding (5), rotor assembly (4), regulator assembly (6) and condenser (suppression capacitor) (7).

Stator assembly (3) consists of a stator core and coils. As the rotor turns, its varying magnetic field causes the stator coil to produce three-phase alternating current (AC).

Rectifier assembly (8) contains three positive diodes and three negative diodes to form the full wave rectifier which is connected to the stator assembly. The 50A alternator has four positive and four negative diodes. Rectifier assembly (8) changes three-phase AC to DC and provides excitation current through three exciter diodes.

Field winding (5) is a stationary coil assembly that provides the magnetic field for the rotor assembly. Rotor assembly (4) provides the north and south poles which cut the magnetic field between the rotor field winding and the stator assembly. The north and south poles are separated by non-magnetic ring (12). Regulator assembly (6) controls alternator output. It is mounted inside the rear frame assembly.

Condenser (7) serves as a suppression capacitor. It protects the alternator diodes from voltage spikes. It also suppresses radio and electronic interference.

Condenser (7) also contains a resistor which is in series with the condenser. The condenser is mounted in the rear frame assembly on top of the regulator assembly.

Alternator Regulator (Bosch)

The voltage regulator is an electronic switch. It feels the voltage in the system and gives the necessary field current (current to the field windings of the alternator) for the alternator to make the needed voltage. The voltage regulator controls the field current to the alternator by switching on and off many times a second.

Regulator (Bosch)

Alternator Regulator (Nippondenso)

The voltage regulator is a solid state (transistor, no moving parts) electronic switch. It feels the voltage in the system and gives the necessary field current (current to the field windings of the alternator) for the alternator to make the needed voltage. The voltage regulator controls the field current to the alternator by switching on and off many times a second. There is no voltage adjustment for this regulator.

Regulator (Nippondenso)

Alternator Regulator (Motorola)

The voltage regulator is not fastened to the alternator, but is mounted separately and is connected to the alternator with wires. The regulator is a solid state (transistor, stationary parts) electronic switch. It feels the voltage in the system and switches on and off many times a second to control the field current (DC current to the field windings) for the alternator to make the needed voltage output. There is a voltage adjustment for this regulator to change the alternator output.

Regulator (Motorola)

Starting System Components

Solenoid

A solenoid is a magnetic switch that does two basic operations:

a. Closes the high current starter motor circuit with a low current start switch circuit.

b. Engages the starter motor pinion with the ring gear.

Typical Solenoid Schematic

The solenoid switch is made of an electromagnet (one or two sets of windings) around a hollow cylinder. There is a plunger (core) with a spring load inside the cylinder that can move forward and backward. When the start switch is closed and electricity is sent through the windings, a magnetic field is made that pulls the plunger forward in the cylinder. This moves the shift lever (connected to the rear of the plunger) to engage the pinion drive gear with the ring gear. The front end of the plunger then makes contact across the battery and motor terminals of the solenoid, and the starter motor begins to turn the flywheel of the engine.

When the start switch is opened, current no longer flows through the windings. The spring now pushes the plunger back to the original position, and, at the same time, moves the pinion gear away from the flywheel.

When two sets of windings in the solenoid are used, they are called the hold-in winding and the pull-in winding. Both have the same number of turns around the cylinder, but the pull-in winding uses a larger diameter wire to produce a greater magnetic field. When the start switch is closed, part of the current flows from the battery through the hold-in windings, and the rest flows through the pull-in windings to motor terminal, then through the motor to ground. When the solenoid is fully activated (connection across battery and motor terminal is complete), current is shut off through the pull-in windings. Now only the smaller hold-in windings are in operation for the extended period of time it takes to start the engine. The solenoid will now take less current from the battery, and heat made by the solenoid will be kept at an acceptable level.

Starter Motor

The starter motor is used to turn the engine flywheel fast enough to get the engine to start running.

The starter motor has a solenoid. When the start switch is activated, the solenoid will move the starter pinion to engage it with the ring gear on the flywheel of the engine. The starter pinion will engage with the ring gear before the electric contacts in the solenoid close the circuit between the battery and the starter motor. When the circuit between the battery and the starter motor is complete, the pinion will turn the engine flywheel. A clutch gives protection for the starter motor so that the engine can not turn the starter motor too fast. When the start switch is released, the starter pinion will move away from the ring gear.

Starter Motor Cross Section
(1) Field. (2) Solenoid. (3) Clutch. (4) Pinion. (5) Commutator. (6) Brush assembly. (7) Armature.

Other Components

Circuit Breaker

Circuit Breaker Schematic
(1) Reset button. (2) Disc in open position. (3) Contacts. (4) Disc. (5) Battery circuit terminals.

The circuit breaker is a switch that opens the battery circuit if the current in the electrical system goes higher than the rating of the circuit breaker.

A heat activated metal disc with a contact point makes complete the electric current through the circuit breaker. If the current in the electrical system gets too high, it cause the metal disc to get hot. This heat causes a distortion of the metal disc which opens the contacts and breaks the circuit. A circuit breaker that is open can be reset (an adjustment to make the circuit complete again) after it becomes cool. Push the reset button to close the contacts and reset the circuit breaker.

Shutoff Solenoid

The rack shutoff solenoid, when activated, moves the shutoff lever in the governor housing which in turn moves the fuel rack to the fuel closed position. The solenoid is activated by a manual control switch.

Wiring Diagrams

Many types of electrical systems are available for these engines. Some charging systems use an alternator and a regulator in the wiring circuit. Others have the regulator inside the alternator. Some starting systems have one starting motor. Engines which must operate in bad starting conditions can have two starting motors. Other starting systems use air or hydraulic motors.

A fuel pressure switch is used in all systems with an external regulator. The switch prevents current discharge (field excitation) to alternator from the battery when the engine is not in operation. In systems where the regulator is part of the alternator, the transistor circuit prevents current discharge to the alternator and the fuel pressure switch is not required.

All wiring schematics are usable with 12, 24, 30 or 32 volts unless the title gives a specific description.

NOTE: Automatic Start-Stop systems use different wiring diagrams. Make reference to the ENGINE ATTACHMENTS section of the Service Manual.

The chart that follows gives the correct wire sizes and color codes.

Grounded Electrical Systems

These systems are used in applications when it is not necessary to prevent radio distortion and/or chemical changes (electrolysis) of grounded components.

(Regulator Inside Alternator)

Charging System
(1) Ammeter. (2) Alternator. (3) Battery.

Charging System With Electric Starter Motor
(1) Start switch. (2) Ammeter. (3) Alternator. (4) Battery. (5) Starter motor.

(Regulator Separate From Alternator)

Charging System
(1) Ammeter. (2) Regulator. (3) Battery. (4) Pressure switch. (5) Alternator.

Charging System With Electric Starter Motor
(1) Start switch. (2) Ammeter. (3) Regulator. (4) Starter motor. (5) Battery. (6) Pressure switch. (7) Alternator.

Insulated Electrical Systems

These systems are most often used in applications where radio interference is not desired or where conditions are such that grounded components will have corrosion from chemical change (electrolysis).

(Regulator Inside Alternator)

Charging System
(1) Ammeter. (2) Alternator. (3) Battery.

Charging System With Electric Starter Motor
(1) Start switch. (2) Ammeter. (3) Alternator. (4) Battery. (5) Starter motor.

(Regulator Separate From Alternator)

Charging System
(1) Ammeter. (2) Regulator. (3) Battery. (4) Pressure switch. (5) Alternator.

Charging System With Electric Starter Motor
(1) Start switch. (2) Ammeter. (3) Regulator. (4) Starter motor. (5) Battery. (6) Pressure switch. (7) Alternator.

Air Starting System

The air starting motor is used to turn the engine flywheel fast enough to get the engine running.

Air Starting System (L.H. Illustrated)
(1) Lubricator. (2) Relay valve. (3) Line. (4) Tee. (5) Starter control valve. (6) Hose. (7) Starting motor. (8) Deflector. (9) Line. (10) Drive housing. (11) Line.

The air starting motor can be mounted on either side of the engine. Air is normally contained in a storage tank and the volume of the tank will determine the length of time the engine flywheel can be turned. The storage tank must hold this volume of air at 1720 kPa (250 psi) when filled.

For engines which do not have heavy loads when starting, the regulator setting is approximately 690 kPa (100 psi). This setting gives a good relationship between cranking speeds fast enough for easy starting and the length of time the air starting motor can turn the engine flywheel before the air supply is gone.

If the engine has a heavy load which can not be disconnected during starting, the setting of the air pressure regulating valve needs to be higher in order to get high enough speed for easy starting.

The air consumption is directly related to speed; the air pressure is related to the effort necessary to turn the engine flywheel. The setting of the air pressure regulator can be up to 1030 kPa (150 psi), if necessary, to get the correct cranking speed for a heavily loaded engine. With the correct setting, the air starting motor can turn the heavily loaded engine as fast and as long as it can turn a lightly loaded engine.

Other air supplies can be used if they have the correct pressure and volume. For good life of the air starting motor, the supply should be free of dirt and water. A lubricator with SAE 10 nondetergent oil [for temperatures above 0°C (32°F)], or diesel fuel [for temperatures below 0°C (32°F)] should be used with the starting system. The maximum pressure for use in the air starting motor is 1030 kPa (150 psi). Higher pressures can cause problems.

Air Starting Motor (6N4147 Illustrated)
(12) Vanes. (13) Rotor. (14) Pinion. (15) Gears. (16) Piston. (17) Spring.

Air for the starting motor comes from a separate air compressor system and is sent through a pressure regulator. From the pressure regulator, air goes through hose (6) to tee (4). The flow of air is then stopped by relay valve (2) until starter control valve (5) is activated. The starter control valve (5) is connected to the air supply line before relay valve (2) by line (3). When starter control valve (5) is activated, air is sent from the starter control valve through line (11) to drive housing (10) then to piston (16) for pinion (14). The air pressure on piston (16) puts spring (17) in compression and puts pinion (14) in engagement with the flywheel gear. When the pinion is in engagement, air then goes from drive housing (10), through line (9) to relay valve (2). This air activates relay valve (2) and lets the main air supply go from tee (4) through lubricator (1) and into starting motor (7).

Flow Of Air Through Starting Motor (Seen from the pinion end of the motor) (Typical Example)

The air with lubrication oil goes into the air motor. The pressure of the air pushes against vanes (12) in rotor (13). This turns the rotor which is connected by gears (15) to starter pinion (14) which turns the engine flywheel. The air then goes out of the starting motor through deflector (8) or an air silencer.

When the engine starts running the flywheel will start to turn faster than starter pinion (14). The pinion (14) retracts under this condition. This prevents damage to the motor, pinion (14) or flywheel gear.

When starter control valve (5) is released, the air pressure and flow to piston (16) behind starter pinion (14) is stopped, piston spring (17) retracts pinion (14). The relay valve (2) stops the flow of air to the air starting motor.