Systems Operation

Usage:

Engine Design

Cylinder And Valve Location

Bore ... 120.7 mm (4.75 in)

Stroke ... 152.4 mm (6.00 in)

Number of Cylinders ... 6

Cylinder Arrangement ... in line

Valves per Cylinder ... 2

Combustion ... Direct Injection

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

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

NOTE: The No. 1 cylinder is opposite the flywheel end.

Fuel System

Fuel Flow

Fuel System Schematic
(1) Fuel tank. (2) Fuel return line. (3) Priming pump. (4) Fuel injection nozzle. (5) Fuel injection line. (6) Fuel injection pump. (7) Primary fuel filter. (8) Check valves. (9) Fuel transfer pump. (10) Secondary fuel filter. (11) Constant bleed valve. (12) Fuel injection pump housing.

Fuel is pulled from fuel tank (1) through primary fuel filter (7) and check valves (8) by fuel transfer pump (9). From the fuel transfer pump the fuel is pushed through secondary fuel filter (10) and to the fuel manifold in fuel injection pump housing (12). A bypass valve in the fuel transfer pump keeps the fuel pressure in the system at 25 to 40 psi (170 to 280 kPa). Constant bleed valve (11) lets a constant flow of fuel go through fuel return line (2) back to fuel tank (1). The constant bleed valve returns approximately 9 gal. (34 liters) per hour of fuel and air to the fuel tank. This helps keep the fuel cool and free of air. There is also a manual bleed valve that can be used when the fuel priming pump is used to remove air from the system. Fuel injection pump (6) gets fuel from the fuel manifold and pushes fuel at very high pressure through fuel line (5) to fuel injection nozzle (4). The 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.

The fuel injection pump is moved by cam (14) of the fuel pump camshaft. When the camshaft turns, the cam raises lifter (11) and pump plunger (6) to the top of the stroke. The pump plunger always makes a full stroke. As the camshaft turns farther, spring (8) returns the pump plunger and lifter to the bottom of the stroke.

When the pump plunger is at the bottom of the stroke, fuel at transfer pump pressure goes into inlet passage (2), around pump barrel (4) and to bypass closed port (5). Fuel fills the area above the pump plunger.

After the pump plunger begins the up stroke, fuel will be pushed out the bypass closed port 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 100 psi (690 kPa), check valve (1) opens and lets fuel flow into the fuel injection line to the fuel injection nozzle. When the pump plunger travels farther up, scroll (9) uncovers spill port (10). The fuel above the pump plunger goes through slot (7), along the edge of scroll (9) and out spill port (10) back to fuel manifold (3). 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.

Fuel Injection Pump
(1) Check valve. (2) Inlet passage. (3) Fuel manifold. (4) Pump barrel. (5) Bypass closed port. (6) Pump plunger. (7) Slot. (8) Spring. (9) Scroll. (10) Spill port. (11) Lifter. (12) Fuel rack. (13) Gear. (14) Cam.

When the pump plunger travels down and uncovers bypass closed port (5), 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 is changed by the rotation of the pump plunger. Gear (13) is attached to the pump plunger and is in mesh with fuel rack (12). The governor moves the fuel rack according to the fuel needs of the engine. When the governor moves the fuel rack, and the fuel rack turns the pump plunger, scroll (9) changes the distance the pump plunger pushes fuel between bypass closed port (5) and spill port (10) opening. The longer the distance from the top of the pump plunger to the point where scroll (9) uncovers spill port (10), the more fuel will be injected.

To stop the engine, the pump plunger is rotated so that slot (7) on the pump plunger is in line with spill port (10). The fuel will now go out the spill port and not to the injection nozzle.

Fuel Injection Nozzle

The fuel injection nozzle goes through the cylinder head 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) Orifice. (6) Valve. (7) Diameter. (8) Spring.

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

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

The injection of fuel continues until the pressure of fuel against diameter (7) becomes less than the force of spring (8). With less pressure against diameter (7), spring (8) pushes valve (6) against the nozzle seat and stops the flow of fuel to the combustion chamber.

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

Fuel Transfer Pump (7N6831)

Fuel Transfer Pump Schematic (Up Stroke)
(1) Bypass valve. (2) Pumping spring. (3) Small piston. (4) Outlet. (5) Inlet check valve. (6) Push plate. (7) Pumping check valve. (8) Outlet check valve. (9) Large piston. (10) Push rod.

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

When the camshaft turns, the cam lifts push rod (10) up. The push rod lifts large piston (9), push plate (6) and small piston (3). As the pistons move up, inlet check valve (5) and outlet check valve (8) close. Pumping check valve (7) in the large piston opens and fuel goes through the holes in the bottom of the large piston and fills the passages and chamber between the bottom of the large piston and outlet check valve (8). As small piston (3) moves up, the pressure of the fuel above the piston increases and flows out of the pump through outlet (4).

Fuel Transfer Pump Schematic (Down Stroke)
(1) Bypass valve. (2) Pumping spring. (3) Small piston. (4) Outlet. (5) Inlet check valve. (6) Push plate. (7) Pumping check valve. (8) Outlet check valve. (9) Large piston. (10) Push rod.

As the camshaft continues to turn, the cam lowers push rod (10) down. Pumping spring (2) pushes small piston (3), push plate (6) and large piston (9) down. When the piston moves down, inlet check valve (5) and outlet check valve (8) open. Pumping check valve (7) in the large piston closes and the pressure of the fuel below the check valve increases. Fuel now flows through the outlet check valve. A part of the fuel goes through outlet (4) and the remainder goes to the area above small piston (3).

As the large piston moves down, fuel from the fuel tank is pulled through inlet check valve (5) into the area between the large and small piston. The pump is now ready to start a new cycle.

Bypass valve (1) controls the outlet pressure of the fuel. If the fuel pressure goes beyond 170 to 280 kPa (25 to 40 psi), the bypass valve opens and fuel flows to the inlet of the pump.

Fuel Transfer Pump (1W1695)

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 Pump And Governor

Oil from the side of the cylinder block goes to support (9) and into the bottom of front governor housing (4). The flow of oil now goes in three different directions.

A part of the oil goes to the rear camshaft bearing in fuel pump housing (5). The bearing has a groove around the inside diameter. Oil goes through the groove and into the oil passage in the bearing surface (journal) of camshaft (7). A drilled passage through the center of the camshaft gives oil to the front camshaft bearing and to the thrust face of the camshaft drive gear. Drain hole (6) in the front of fuel pump housing (5) keeps the level of the oil in the housing even with the center of the camshaft. The oil returns to the oil pan through the timing gear housing.

Fuel Pump And Governor
(1) Fuel ratio control. (2) Servo. (3) Rear governor housing. (4) Front governor housing. (5) Fuel pump housing. (6) Drain hole. (7) Camshaft. (8) Drain hole. (9) Support.

Oil also goes from the bottom of the front governor housing through a passage to the fuel pump housing and to governor servo (2). The governor servo gives hydraulic assistance to move the fuel rack.

The remainder of the oil goes through passages to the rear of rear governor housing (3), through fuel ratio control (1) and back into another passage in the rear governor housing. Now the oil goes into the compartment for the governor controls. Drain hole (8) keeps the oil at the correct level. The oil in this compartment is used for lubrication of the governor control components and the oil is the supply for the dashpot.

The internal parts of the governor are lubricated by oil leakage from the servo and the oil is thrown by parts in rotation. The flyweight carrier thrust bearing gets oil from the passage at the rear of the camshaft.

Oil from the governor returns to the oil pan through a hole in the bottom of the front governor housing and through passages in the support and cylinder block.

Governor

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 (10) 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.

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) Riser. (11) Spring seat. (12) Stop bolt. (13) Load stop bar. (14) Power setting screw. (15) Stop collar. (16) Torque spring. (17) Torque rise setting screw. (18) Stop bar.

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 started and the governor is at the 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 (10) toward the flyweights. When the riser moves forward, lever (7) moves sleeve (2) and valve (3) toward the rear. 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.

Engines With Stop Bar

Engines With Torque 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 (10) forward and increases the amount of fuel to the engine. As the load is increased more, governor spring (1) pushes riser (10) farther forward. Spring seat (11) pulls on stop bolt (12). Stop collar (15) on the opposite end has power setting screw (14) and torque rise setting screw (17) that control the maximum amount of fuel rack travel. The power setting screw moves forward and makes contact with torque spring (16). This is the full load balance point. If more load is added to the engine, engine speed will decrease and push riser (10) forward more. This will cause fuel setting screw (14) to bend (deflect) torque spring (16) until torque rise setting screw makes contact with stop bar (18). This is the full load balance point.

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 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 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 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 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

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

Dashpot (Governor Moving to Fuel On)
(1) Cylinder. (2) Piston. (3) Dashpot spring. (4) Spring seat. (5) Needle valve. (6) Check valve. (7) Oil reservoir.

When the governor moves toward FUEL ON, spring seat (4) and piston (2) move to the right. This movement pulls oil from oil reservoir (7) through check valve (6) and into cylinder (1).

Dashpot (Governor Moving to Fuel Off)
(1) Cylinder. (2) Piston. (3) Dashpot spring. (4) Spring seat. (5) Needle valve. (6) Check valve. (7) Oil reservoir.

When the governor moves toward FUEL OFF, spring seat (4) and piston (2) move to the left. This movement pushes oil out of cylinder (1), through needle valve (5) and into oil reservoir (7).

If the governor movement is slow, the oil gives no restriction to the movement of the piston and spring seat. If the governor movement is fast in the FUEL OFF direction, the needle valve gives a restriction to the oil and the piston and spring seat will move slowly.

Automatic Timing Advance Unit

Automatic Timing Advance Unit
(1) Weights. (2) Springs. (3) Slides. (4) Dowels. (5) Automatic timing advance unit.

The automatic timing advance unit (5) is installed on the front of the fuel pump drive shaft.

The weights (1) in the timing advance are driven by two slides (3) that fit into notches made on an angle in the weights (1). The slides (3) are driven by two dowels (4) in the hub assembly of the gear assembly in the automatic timing advance unit (5). As centrifugal force (rotation) moves weights (1) outward against the force of springs (2), the movement of the notches in the weights (1) will cause the slides (3) to make a change in the angle between the timing advance gear and the two drive dowels (4) in the hub assembly. Since the automatic timing advance unit (5) drives the fuel pump drive shaft, which is connected to the fuel injection pump camshaft, the fuel injection timing is also changed.

Governor Control-Low Speed Regulation

There are applications where the engine is used to power the truck and also used as a stationery engine. Engines used in this application will have a control group installed on the rear of the standard governor. The control group is not used when the truck is operating, but can be engaged by air pressure for use with a stationary application. The function of the control group is to set the engine rpm at 1600 with no load and through a lever assembly connection with the standard governor spring, control engine speed within 5% regulation.

Operation

During normal operation, spring (1) holds piston assembly (2) forward far enough so that lever (3) does not touch low speed governor spring (4). This allows for normal governor operation.

Governor Control-Not Engaged (normal operation)
(1) Spring. (2) Piston assembly. (3) Lever. (4) Low speed governor spring.

When the engine is used as a stationary engine, air pressure is used to engage the governor control (5). The air pressure moves piston assembly (2) to the rear and holds the piston assembly against adjusting screw (6). Movement of the piston to the rear causes low speed governor spring (4) to contact lever (3) which moves governor spring (7) in maximum fuel direction. When the engine speed reaches 1600 rpm the force of the governor springs are in balance to hold the engine at that speed.

Governor Control-Engaged (stationary operation)
(2) Piston assembly. (3) Lever. (4) Low speed governor spring. (5) Governor control. (6) Adjusting screw. (7) Governor spring.

When a load is applied to the engine the engine speed reduces to 1500 rpm to supply the required horsepower to operate the load. When the load is removed the low speed governor spring reacts against the governor spring to hold engine overspeed to 1600 rpm where the engine will remain until the load is applied again or the governor control is disengaged.

Fuel Ratio Control

Fuel Ratio Control (Engine Started)
(1) Inlet air chamber. (2) Diaphragm assembly. (3) Internal valve. (4) Oil drain passage. (5) Oil inlet. (6) Stem. (7) Spring. (8) Piston. (9) Oil passage. (10) Oil chamber. (11) Lever.

The fuel ratio control limits the amount of fuel to the cylinders during an increase of engine speed (acceleration) to reduce exhaust smoke. Properly adjusted it also minimizes the amount of soot in the engine.

Stem (6) moves lever (11) which will restrict the movement of the fuel rack in the FUEL ON direction only.

With the engine stopped, there is no oil pressure and stem (6) is in the fully extended position as in the (Engine Started) illustration. The movement of the fuel rack and lever (11) is not restricted by stem (6). This gives maximum fuel to the engine for easier starts.

After the engine is started, engine oil flows through oil inlet (5) into pressure oil chamber (10). From oil chamber (10) oil flows through oil passage (9) into internal valve (3) and out oil drain passages in stem (6).

Stem (6) will not move until inlet manifold pressure increases enough to move internal valve (3). A line connects the inlet manifold with inlet air chamber (1) of the fuel ratio control.

Fuel Ratio Control (Control Activated)
(1) Inlet air chamber. (2) Diaphragm assembly. (3) Internal valve. (4) Oil drain passage. (5) Oil inlet. (6) Stem. (7) Spring. (8) Piston. (9) Oil passage. (10) Oil chamber. (11) Lever.

When the manifold pressure increases, it causes diaphragm assembly (2) to move towards the right. This also causes internal valve (3) to move to the right. When internal valve (3) moves to the right, it closes oil passage (9).

When oil passage (9) is closed, oil pressure increases in oil chamber (10). Oil pressure moves piston (8) and stem (6) to the left and into the operating position. The fuel ratio control will remain in the operating position until the engine is shut off or the inlet manifold pressure increases with the addition of more load on the engine.

Fuel Ratio Control (Engine Acceleration)
(1) Inlet air chamber. (2) Diaphragm assembly. (3) Internal valve. (4) Oil drain passage. (5) Oil inlet. (6) Stem. (7) Spring. (8) Piston. (9) Oil passage. (10) Oil chamber. (11) Lever.

When the governor control is moved to increase fuel to the engine, stem (6) limits the movement of lever (11) in the FUEL ON direction. The oil in oil chamber (10) acts as a restriction to the movement of stem (6) until inlet air pressure increases.

As the inlet air pressure increases, diaphragm assembly (2) and internal valve (3) move to the right. The internal valve opens oil passage (9), and oil in oil chamber (10) goes to oil drain passage (4). With the oil pressure reduced behind piston (8), spring (7) moves the piston and stem (6) to the right. Piston (8) and stem (6) will move until oil passage (9) is closed by internal valve (3). Lever (11) can now move to let the fuel rack go to the full fuel position. The fuel ratio control is designed to restrict the fuel until the air pressure in the inlet manifold is high enough for complete combustion. It prevents large amounts of exhaust smoke caused by an air-fuel mixture with too much fuel.

Torque Limiter

The 9N6232 Torque Limiter Control Group serves as a pressure control valve between the inlet manifold and the fuel ratio control. It regulates the pressure signal to the fuel ratio depending on boost and engine speed. Without this device, the fuel ratio control is able to limit rack movement according to engine speed. By also controlling rack movement according to engine speed, it is possible to restrict the fuel supply to the engine at low engine speed, thus avoiding excessive smoke from unburnt fuel.

Torque Limiter
(1) Air inlet. (2) Screw. (3) Spring. (4) Passage. (5) Outlet. (6) Spool. (7) Passage. (8) Flyweights.

Air from the inlet manifold enters the torque limiter at inlet (1) and is permitted to pass to the outlet (5) to the fuel ratio control only if the land on spool (6) opens passage (7) to the outlet in the valve assembly. The position of the spool depends on the balance of forced from the rotating flyweights (8) and opposed by spring (3) (adjustable by screw (2)) and outlet air pressure exerted on the spool through passage (4).

Air Inlet And Exhaust System

Jacket Water Aftercooler System

Air Inlet And Exhaust System - Jacket Water Aftercooler System
(1) Jacket water aftercooler housing. (2) Exhaust outlet. (3) Turbine wheel housing. (4) Air outlet. (5) Compressor wheel housing. (6) Air inlet. (7) Cylinder head. (8) Exhaust manifold. (9) Exhaust inlet. (10) Cylinder bore.

Turbocharger
(1) Jacket water aftercooler housing. (2) Exhaust outlet. (3) Turbine wheel housing. (4) Air outlet. (5) Compressor wheel housing. (6) Air inlet. (8) Exhaust manifold. (9) Exhaust inlet.

Jacket Water Aftercooler
(1) Jacket water aftercooler housing. (3) Turbine wheel housing. (4) Air outlet. (7) Cylinder head.

The air inlet and exhaust system components are: air cleaner, aftercooler (if so equipped), inlet manifold, cylinder head, valves and valve system components, exhaust manifold and turbocharger. Clean inlet air from the air filter is pulled through air inlet (6) of the turbocharger by the turning compressor wheel. The compression wheel compresses the inlet air. On engines with a jacket water aftercooler system, the air goes to the aftercooler housing (1). The aftercooler cools the air to approximately 93°C (200°F). The air is then routed to the inlet manifold which is part of cylinder head (7).

Air To Air Aftercooled System

Air To Air Aftercooled Schematic

Air Inlet And Exhaust System Schematic
(1) Exhaust manifold. (2) Aftercooler/Inlet manifold. (5) Exhaust outlet. (6) Turbine side of turbocharger. (7) Compressor side of turbocharger. (8) Air inlet. (9) Exhaust valve. (10) Intake valve.

In the air to air aftercooler system, compressed turbocharger air is directed to a chassis mounted cooler in front of the radiator. Ambient temperature air is moved across the aftercooler to lower the inler air temperature to approximately 43°C (110°F). The air then goes to inlet manifold (2) which is part of the cylinder head. Cooling of the inlet air increases combustion efficiency, which helps to lower fuel consumption and increase horsepower output.

When intake valves (10) open, the air goes into the engine cylinder and is mixed with the fuel for combustion. When exhaust valves (9) open, the exhaust gases go out of the engine cylinder and into exhaust manifold (1). From the exhaust manifold, the exhaust gases go through the blades of the turbine wheel. This causes the turbine wheel and compressor wheel to turn. The exhaust gases then go out exhaust outlet (3) of the turbocharger.

Turbocharger

The turbocharger is installed on the exhaust manifold. All the exhaust gases from the engine go through the turbocharger.

Turbocharger (Typical Example)
(1) Air inlet. (2) Compressor housing. (3) Nut. (4) Compressor wheel. (5) Thrust bearing. (6) Center housing. (7) Lubrication inlet passage. (8) Turbine housing. (9) Sleeve. (10) Turbine wheel. (11) Exhaust outlet. (12) Sleeve. (13) Oil deflector. (14) Bearing. (15) Lubrication outlet passage. (16) Bearing. (17) Exhaust inlet.

The exhaust gases enter the turbine housing (8) and go through the blades of turbine wheel (10), causing the turbine wheel and compressor wheel (4) to turn.

When the compressor wheel turns, it pulls filtered air from the air cleaners through the compressor housing air inlet. The air is put in compression by action of the compressor wheel and is pushed to the inlet manifold of the engine.

When engine load increases, more fuel is injected into the engine cylinders. The volume of exhaust gas increases which causes the turbocharger turbine wheel and compressor impeller to turn faster. The increased rpm of the impeller increases the quantity of inlet air. As the turbocharger provides additional inlet air, more fuel can be burned. This results in more horsepower from the engine.

Maximum rpm of the turbocharger is controlled by the rack setting, the high idle speed setting and the height above sea level at which the engine is operated.

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NOTICE

If the high idle rpm or the fuel setting is higher than given in the Fuel Setting And Related Information Fiche (for the height above sea level at and which the engine is operated), there can be damage to engine or turbocharger parts. Damage will result when increased heat and/or friction, due to the higher engine output, goes beyond the engine cooling and lubrication systems abilities.

The bearings for the turbocharger use engine oil for lubrication. The oil comes in through the lubrication inlet passage (7) and goes through passages in the center section for lubrication of the bearings. Oil from the turbocharger goes out through the lubrication outlet passage (15) in the bottom of the center section and goes back to the engine lubrication system.

Cylinder Head And Valves

There is one cylinder head for all cylinders. Each cylinder has one intake and one exhaust valve. Each intake and exhaust valve has a valve rotator. The valve rotator causes the valve to turn a small amount each time the valve opens and closes. This action helps keep carbon deposits off of the valve face and valve seat.

The cylinder head has valve seats installed and they can be replaced.

The valve guides can be replaced. There are threads on the inside diameter of the valve guides to hold oil that lubricates the valve stem.

Valve Mechanism

The valve mechanism controls the flow of inlet air and exhaust gases in and out of the cylinders. The valve mechanism consists of rocker arms, push rods, valve lifters and camshaft.

The camshaft is driven by and timed to the crankshaft. When the camshaft turns, the camshaft lobes move the valve lifters up and down. The valve lifters move the push rods which move the rocker arms. Movement of the rocker arms make the intake and exhaust valves open according to the firing order (injection sequence) of the engine. A valve spring for each valve makes the valve go back to the closed position and holds it there.

Lubrication System

System Oil Flow

Lubrication System Schematic (Engine Warm)
(1) Oil passage (to front idler gear). (2) Oil passage (to turbocharger and fuel injection pump). (3) Rocker arm shaft. (4) Oil pressure connection. (5) Oil manifold. (6) Piston cooling orifices. (7) Camshaft bearing bore. (8) Oil cooler bypass valve. (9) Oil filter bypass valve. (10) Engine oil cooler. (11) Oil filter. (12) Turbocharger. (13) Oil pump. (14) Oil pan.

Oil pump (13) pulls oil from oil pan (14) and then pushes the oil to oil cooler (10). From the oil cooler the oil goes to oil filter (11) and then to oil manifold (5). From the oil manifold, oil goes to all main bearings, and piston cooling orifices (6). Oil passages in the crankshaft send oil to the connecting rod bearings. Oil from the front main bearing goes through oil passage (1) to the bearing for the fuel injection pump idler gear.

Oil from the front main bearing also goes to camshaft bearing bore (7). The front camshaft bearing is the only bearing to get pressure lubrication.

Oil passage (2) from No. 4 main bearing sends oil to turbocharger (12) and the fuel injection pump housing on the right side of the engine.

An oil passage from the rear of the cylinder block goes below the head bolt hole and connects with a drilled passage that goes up next to the head bolt hole. A hollow dowel connects the vertical oil passage in the cylinder block to the oil passage in the head. The spacer plate has a hole with a counterbore on each side that the hollow dowel goes through. An O-ring is in each counterbore to prevent oil leakage around the hollow dowel. Oil flows through the hollow dowel into a vertical passage in the cylinder head to the rocker arm shaft bracket. The rocker arm shaft has an orifice to restrict the oil flow to the rocker arms. The rear rocker arm bracket also has an O-ring that seals against the head bolt. This seal prevents oil from going down around the head bolt and leaking past the head gasket or spacer plate gasket. The O-ring must be replaced each time the head bolt is removed from the rear rocker arm bracket.

Rocker Arm Oil Supply

Holes in the rocker arm shafts let the oil give lubrication to the valve system components in the cylinder head.

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

There is a bypass valve in the oil pump. This bypass 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 increases and the bypass valve will open. This allows the oil that is not needed to go back to the engine oil pan.

With the engine cold (starting conditions), bypass valves (8 and 9) will open and give immediate lubrication to all components when cold oil with high viscosity causes a restriction to the oil flow through oil cooler (10) and oil filter (11). Oil pump (13) sends the cold oil through the bypass valves around the oil cooler and oil filter to oil manifold (5) in the cylinder block.

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

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 lubrication of the engine.

Flow Of Oil (Engine Cold)
(8) Oil cooler bypass. (9) Oil filter bypass. (10) Engine oil cooler. (11) Oil filter. (12) Turbocharger. (13) Oil pump. (14) Oil pan.

Cooling System

Cooling System Schematic
(1) Radiator top tank. (2) Shunt line. (3) Coolant outlet. (4) Regulator to aftercooler vent line. (5) Water temperature regulator. (6) Inlet line to aftercooler. (7) Aftercooler to radiator vent line. (8) Jacket water aftercooler. (9) Cylinder head. (10) Radiator. (11) Water pump. (12) Return line from aftercooler. (13) Cylinder block. (14) Cylinder liner. (15) Coolant inlet. (16) Oil cooler. (17) Bonnet.

Coolant Flow
(3) Coolant outlet. (5) Water temperature regulator. (6) Inlet line to aftercooler. (8) Jacket water aftercooler. (9) Cylinder head. (11) Water pump. (12) Return line from aftercooler. (13) Cylinder block. (15) Coolant inlet. (16) Oil cooler. (17) Bonnet. (18) Internal bypass. (19) Air compressor. (20) Outlet hose from air compressor. (21) Inlet hose to air compressor.

All Caterpillar Truck engines must have shunt type cooling systems. This type cooling system helps prevent pump cavitation (air bubbles caused by low pressure). It keeps a positive pressure of coolant at the inlet of the pump at all times.

Water pump (11) is on the left front side of the engine. It is gear driven by the timing gears. Coolant from the bottom of the radiator (10) goes to the water pump inlet. The rotation of the impeller in water pump (11) pushes the coolant through the system.

If the engine is equipped with a jacket water aftercooler (8), some of the coolant flow goes through inlet line (6) for the aftercooler and into jacket water aftercooler (8). As the coolant goes through jacket water aftercooler (8), it cools the inlet air for the engine. The coolant comes out of jacket water aftercooler (8) through return line (12) and into bonnet (17). In bonnet (17) the coolant flow from the aftercooler mixes with the rest of the coolant flow from water pump (11). This other flow came through engine oil cooler (16). Bonnet (17) sends the coolant into block (13).

NOTE: If the engine is equipped with and air to air aftercooler system, a coolant mixture with a minimum of 30% ethylene glycol base antifreeze must be used for efficient water pump performance. This mixture keeps the cavitation temperature range of the coolant high enough for efficient performance. Dowtherm 209 antifreeze can not be used because it does not raise the water pump cavitation temperature of the coolant high enough.

Inside cylinder block (13) the coolant goes around cylinders (14) and up through the water directors into cylinder head (9). The water directors send the flow of coolant around the valves and passages for exhaust gases in cylinder head (9). Here the water temperature regulator (5) controls the direction of the flow. If the coolant temperature is less than normal for engine operation, water temperature regulator (5) is closed. The only way for the coolant to get out of cylinder head (9) is through the internal bypass. The coolant goes through the internal bypass into water pump (11). Water pump (11) pushes the coolant through the cooling system again. When the coolant gets to the correct temperature, water temperature regulator (5) opens and coolant flow is divided. Most of the coolant goes to the lower chamber of radiator top tank (1) and through the radiator. The remainder goes through the internal bypass to water pump (11). The amount of the two flows is controlled by water temperature regulator (5).

NOTE: The water temperature regulator (5) is an important part of the cooling system. It divides coolant flow between the radiator and internal bypass as necessary to maintain the correct temperature. If the water temperature regulator is not installed in the system, there is no mechanical control, and most of the coolant will take the path of least resistance through the bypass. This will cause the engine to overheat in hot weather. In cold weather, even the small amount of coolant that goes through the radiator is too much, and the engine will not get to normal operating temperatures.

Radiator top tank (1) is divided into two chambers (upper and lower) by a baffle. A small air and coolant vent tube connects them. Shunt line (2) is located as low as possible in the upper chamber. As coolant comes into the lower chamber of radiator top tank (1), the coolant which has air in it flows through the vent tube to the top chamber. The air makes a separation from the coolant in the top chamber. The coolant flows down shunt line (2) to the pump inlet. The air stops in the upper chamber until there is enough pressure for it to leak out the radiator cap.

Earlier engines have vent lines inside to let the air out when the cooling system is filled. Later engines have the vent lines on the outside. The standard 3306B Truck Engine must have a vent line from the regulator housing to the top of the radiator. The 3306B Truck engine with aftercooler (8) must have vent line (4) from the regulator housing to jacket water aftercooler housing (8). It also must have vent line (7) from jacket water aftercooler housing (8) to the top of radiator (10).

Coolant For Air Compressor

Coolant Flow In Air Compressor
(19) Air compressor. (20) Outlet hose. (21) Inlet hose.

The coolant for the air compressor (19) comes from the cylinder block through hose (21) and into the air compressor. The coolant goes from the air compressor through hose (20) back into the front of the cylinder head.

Cooling System Components

Water Pump

The centrifugal-type water pump has two seals, one prevents leakage of water and the other prevents leakage of lubricant.

An opening in the bottom of the pump housing allows any leakage at the water seal or the rear bearing oil seal to escape.

Fan

The fan is driven by two V-belts, from a pulley on the crankshaft and the fan drive. Belt tension is adjusted by moving the alternator.

Basic Block

Cylinder Block And Liners

A steel spacer plate is used between the cylinder head 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 piston has three rings; two compression and one oil ring. All rings are located above the piston pin bore. The two compression rings seat in an iron band which is cast into the piston. The pistons use compression rings which are of the KEYSTONE type. 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 pin bore in the piston is offset (moved away) from the center of the piston 0.76 mm (.030 in). The full floating piston pin is held in the piston by two snap rings which fit into grooves in the piston pin bore.

The piston pin end of the connecting rod is tapered to give more bearing surface at the area of highest load. The connecting rod is installed on the piston with the bearing tab slots on the same side as the "V" mark on the piston.

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 that drives the timing gears and the engine oil pump. The connecting rod bearing surfaces get oil for lubrication through passages drilled in the crankshaft. A lip type seal and wear sleeve is used to control oil leakage in the front crankshaft seal. A hydrodynamic grooved seal assembly is used to control rear crankshaft oil leakage. The hydrodynamic grooves in the seal lip move lubrication oil back into the crankcase as the crankshaft turns.

Vibration Damper

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

Cross Section Of A Vibration Damper
(1) Weight. (2) Case.

The vibration damper is installed on the front of the crankshaft. The damper has a weight in a metal housing. The space between the weight and the housing is filled with a thick fluid. The weight moves in the housing to limit the torsional vibration.

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NOTICE

Inspect the viscous damper for signs of leakage or a dented (damaged) case (2). Either condition can cause weight (1) to make contact with the case and affect damper operation.

Electrical System

The engine 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), disconnect switch, 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.

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NOTICE

The disconnect switch, if so equipped, must be in the ON position to let the electrical system function. There will be damage to some of the charging circuit components if the engine is running with the disconnect switch in the OFF position.

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

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NOTICE

Never operate the alternator without the battery in the circuit. Making or breaking an alternator connection with heavy load on the circuit can cause damage to the regulator.

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 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. 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.

Alternator (Nippondenso)

The alternator is driven by V-belts from the crankshaft pulley. The Nippondenso alternator has three-phase, full-wave rectified output. It is brushless. The rotor and bearings are the only moving parts. The regulator is part of the alternator.

Nippondenso Alternator
(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.

When the engine is started and the rotor turns inside the stator windings, three-phase alternating current (AC) and rapidly rising voltage is generated.

A small amount of alternating current (AC) is changed (rectified) to pulsating direct current (DC) by the exciter diodes on the rectifier assembly. Output current from these diodes adds to the initial current which flows through the rotor field windings from residual magnetism. This will make the rotor a stronger magnet and cause the alternator to become activated automatically. As rotor speed, current and voltages increase, the rotor field current increases enough until the alternator becomes fully activated.

The main battery charging current is charged (rectified) from AC to DC by the other positive and negative diodes in the rectifier and pack (main output diodes) which operate in a full wave linkage rectifier circuit.

Alternator output is controlled by a regulator, which is inside the alternator rear frame.

Alternator Regulator (Delco-Remy)

Regulator (Delco-Remy)

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.

Alternator Regulator (Bosch)

Regulator (Bosch)

Alternator Regulator (Nippondenso)

Regulator (Nippondenso)

The regulator is fastened to the alternator by two different methods. One method fastens the regulator to the top, rear of alternator. With the other method the regulator is fastened separately by use of a wire and a connector that goes into the alternator.

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.

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 windings and the pull-in windings. Both have the same number of turns around the cylinder, but the pull-in windings 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 cannot 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 circuit through the circuit breaker. If the current in the electrical system gets too high, it causes 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.

Jake Brake

The JAKE BRAKE permits the operator to control the speed of the vehicle on grades, curves, or anytime when speed reduction is necessary, but long applications of the service brakes are not desired. In downhill operation, or any slow down condition, the engine crankshaft is turned by the rear wheels (through the differential, driveshaft, transmission and clutch). To reduce the speed of the vehicle, an application of a braking force can be made to the pistons of the engine.

The JAKE BRAKE, when activated, does this through the conversion of the engine from a source of power to an air compressor that absorbs (takes) power. This conversion is made possible by a master to slave piston arrangement, where movement of the rocker arm for the exhaust valve of one cylinder is transferred hydraulically to open the exhaust valve of another cylinder near the top of its normal compression stroke cycle. The compressed cylinder charge is now released into the exhaust manifold.

The release of the compressed air pressure to the atmosphere prevents the return of energy to the engine piston on the expansion (power) stroke. The result is an energy loss, since the work done by the compression of the cylinder charge is not returned by the expansion process. This energy loss is taken from the rear wheels, which provides the braking action for the vehicle.

Jake Brake Components

Jake Brake Installed (Typical Example)
(1) Rear housing. (2) Front housing. (3) Stud. (4) Support bracket.

The JAKE BRAKE consists of two different housings installed in the valve mechanism compartment above the rocker arms and rocker arm shaft. Each housing is positioned over three cylinders, and is mounted on a support bracket (4) at the end rocker shaft brackets. Special exhaust rocker arm adjusting screws and exhaust valve bridges are necessary.

NOTE: Only the engine valves and valve mechanism for the exhaust side of the cylinders are used in the operation of the JAKE BRAKE.

A spacer is used between cylinder head and the valve cover to permit installation of the valve cover. The increase in height with the JAKE BRAKE installed is 90 mm (3.5 in).

Both the front and rear JAKE BRAKE housing consist of the parts that follow: three master pistons, three slave pistons, three control valves, and one solenoid valve.

Jake Brake Operation

The JAKE BRAKE operates with engine oil which is supplied from the rocker arm shafts. Solenoid valve (1) controls the oil flow in the housing.

When the solenoid is activated, solenoid valve (1) moves down and closes the oil drain passage to the oil pan. At the same time, it opens low pressure oil passage (15) to three control valves (3). As low pressure passage (15) is filled with engine oil, control valves (3) are pushed up in their chamber against force of spring (2). At this position, a groove in control valve (3) is in alignment with high pressure oil passage (4) that supplies slave piston (10) and master piston (6). Engine oil pressure will now lift ball check valve (13) and fill high pressure oil passage (4) and the chambers behind the slave and master pistons. This pressure moves the pistons down to a position where they will now make contact with the engine valve mechanism. When the oil pressure is the same through all the oil passages, the small spring will force ball check valve (13) back against its seat. The system is now completely charged and ready for operation with engine valve mechanism. When the solenoid is activated, the JAKE BRAKE is ready to operate in approximately 1/5 of a second.

Master-Slave Circuit Schematic
(1) Solenoid valve. (2) Spring. (3) Control valve. (4) High pressure oil passage. (5) Slave piston adjustment screw. (6) Master piston. (7) Spring. (8) Rocker arm adjustment screw. (9) Rocker arm. (10) Slave piston. (11) Exhaust push rod. (12) Exhaust valves. (13) Ball check valve. (14) From manually operated control switch. (15) Low pressure oil passage.

Oil Passage Schematic (Front Housing Shown)
(1) Solenoid valve. (3) Control valves. (4) High pressure oil passage. (6) Master pistons. (10) Slave pistons. (15) Low pressure oil passage.

When engine push rod (11) for the exhaust valve begins to move up on its normal exhaust cycle, rocker arm (9) and rocker adjustment screw (8) move up to make contact with master piston (6). As master piston (6) begins to move up, the oil pressure increases in passage (4) because ball check valve (13) will not let the oil out. Since there is a constant increase in pressure with the rocker arm movement, slave piston (10) is forced down with enough force to open exhaust valves (12).

This master-slave circuit is designed so that master piston (6) is only moved by an engine cylinder on the exhaust stroke, while slave piston (10) opens only the exhaust valves of an engine cylinder on the compression stroke (just before top center). The braking force is constant, and the sequence is the same as the firing order of the engine, as shown in the chart that follows:

When solenoid valve (1) is in the off position, the engine oil supply passage is closed, and the oil drain passage to the oil pan is opened. This lets the oil drain from beneath control valve (3), and spring (2) pushes control valve (3) to bottom of chamber. This position lets the oil from high pressure oil passage (4) to drain into chamber above the control piston. Spring (7) now moves master piston (6) up to its neutral position, away from rocker arm adjustment screw (8). The time necessary for the system to stop operation is approximately 1/10 of a second. The JAKE BRAKE will not be able to operate now until the solenoid is activated again.

Jake Brake Controls

The JAKE BRAKE is activated electrically with three different switches connected in series in the circuit. A manually operated control switch (2) is located on the dash of the vehicle. This is a three position switch that permits an operator a selection of 100 %, 50 %, or no retardation (braking force).

The fuel pump switch (6), permits JAKE BRAKE operation only when throttle is at idle position. Any application of more throttle (fuel increase) will stop current flow and the JAKE BRAKE will not operate.

The next switch in series is clutch switch (4). Clutch switch (4) is set to permit brake operation only when the clutch is engaged. This prevents engine stall by the JAKE BRAKE when the drive line is not engaged with the engine.

Fuel pump (6) and clutch switch (4) work automatically after the operator control switch (2) is manually positioned. This control circuit permits any one of the three switches to prevent operation of the brake, but requires all three of the switches to be closed before operation can begin.

A small diode (6) is connected between the load side of switch terminal and ground to protect the switch contacts from arcing.

Control Circuit Schematic
(1) To solenoid valve. (2) Control switch (on dash). (3) Diode. (4) Clutch switch. (5) Circuit breaker. (6) Fuel pump switch. (7) Battery.