Systems Operation



NOTE: For Specifications with illustrations, make reference to the SPECIFICATIONS for D349 INDUSTRIAL AND MARINE ENGINES, Form No. SENR7108. If the Specifications in Form SENR7108 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 in the book with the latest date.

Fuel System

1. Fuel transfer pump inlet fuel line. 2. Fuel priming pump. 3. Fuel supply line from fuel tank. 4. Air-fuel bleed line from fuel control valve housing to fuel tank. 5. Fuel tank. 6. Fuel transfer pump outlet line to fuel filter housing. 7. Fuel transfer pump. 8. Fuel filters. 9. Fuel injection pump housing.

1. Fuel transfer pump inlet fuel line. 2. Fuel priming pump. 3. Fuel supply line from fuel supply tank. 6. Fuel transfer pump outlet line to fuel filter housing. 8. Fuel filters. 10. Air-fuel bleed line to fuel tank. 11. Fuel control valve. 12. Spring.

The position of valve (11) controls the flow of fuel in this fuel system. With the engine stopped, spring (12) holds valve (11) in the closed position.

1. Fuel transfer pump inlet fuel line. 2. Fuel priming pump. 3. Fuel supply line from fuel supply tank. 6. Fuel transfer pump outlet line to fuel filter housing. 8. Fuel filters. 10. Air-fuel bleed line to fuel tank. 11. Fuel control valve. 12 & 13. Springs.

As the priming pump handle is pulled out (suction stroke) springs (12 and 13) expand and valve (11) moves, allowing fuel from supply line (3) to be drawn into fuel priming pump (2).

When the priming pump handle is pushed in (pressure stroke), the combination of fuel pressure and spring (12) force causes valve (11) to move, compressing spring (13). This action allows the required amount of fuel to flow through fuel filters (8) and on to the injection pumps. At the same time, excess fuel and any air that may be in the system flows through air-fuel bleed line (10) to return to the fuel supply tank.

1. Fuel transfer pump inlet fuel line. 2. Fuel priming pump. 3. Fuel supply line from fuel supply tank. 6. Fuel transfer pump outlet line to fuel filter housing. 8. Fuel filters. 10. Air-fuel bleed line to fuel tank. 11. Fuel control valve. 12. Spring. 13. Spring.

With the engine running, only the fuel required to maintain the desired engine speed is directed through the fuel filters and then to the fuel injection pump. Fuel not required by the engine is directed through passages, opened by the position of fuel control valve (11), and returns to the fuel transfer pump. At the same time, some fuel and any air that may be in the system returns to the fuel supply tank through air-fuel bleed line (10).

1. Fuel transfer pump inlet fuel line. 2. Fuel priming pump. 3. Fuel supply line from fuel supply tank. 6. Fuel transfer pump outlet line to fuel filter housing. 8. Fuel filters. 10. Air-fuel bleed line to fuel tank. 11. Fuel control valve.

Fuel Injection Pump

Fuel enters the fuel injection pump housing through passage (6) and enters the fuel injection pump body through the inlet port (2). The injection pump plungers (5) and the lifters (11) are lifted by the cam lobes (12) on the camshaft and always make a full stroke. The lifters are held against the cam lobes by the springs (3). Each pump measures the amount of fuel to be injected into its respective cylinder and forces it out the fuel injection nozzle.

1. Check valve. 2. Inlet port. 3. Spring. 4. Lubrication passage (fuel). 5. Pump plunger. 6. Fuel passage. 7. Bleed passage. 8. Fuel rack. 9. Lubrication passage (oil). 10. Gear segment. 11. Pump Lifter. 12. Camshaft lobe.

The amount of fuel pumped each stroke is varied by turning the plunger in the barrel. The plunger is turned by the governor action through the fuel rack (8) which turns the gear segment (10) on the bottom of the pump plunger. Passage (4) provides fuel to lubricate the pump plunger and passage (7) allows air to be bled from the system through the valve on top of the fuel filter case.

Fuel Injection Valve

Fuel, under high pressure from the injection pumps, is transferred through the injection lines to the injection valves. As high pressure fuel enters the nozzle assembly, the check valve within the nozzle opens and permits the fuel to enter the precombustion chamber. The injection valve provides the proper spray pattern.

1. Fuel line assembly. 2. Seal. 3. Body. 4. Nut. 5. Seal. 6. Nozzle assembly. 7. Glow plug. 8. Precombustion chamber.

Speed Sensing, Variable Timing Unit

The variable timing unit, couples the fuel injection pump camshaft to the engine rear timing gears. The variable timing unit advances the timing as engine rpm increases.

On earlier engines the timing advances from 11° BTC at low idle to 19° BTC at high idle. On later engines the timing advances from 8° BTC at low idle to 19° BTC at high idle.

During engine low rpm operation, the flyweight (8) force is not sufficient to overcome the force of control valve spring (3) and move control valve (7) to the closed position. Oil merely flows through the power piston cavity (2).

1. Power piston. 2. Power piston cavity. 3. Control valve spring. 4. Power piston return spring. 5. Oil inlet passage. 6. Drain port. 7. Control valve. 8. Flyweights. 9. Shaft assembly.

As the engine rpm increases, flyweights (8) overcome the force of control valve spring (3) and move control valve (7) to the closed position, blocking the oil drain port (6). Pressurized oil, trapped in power piston cavity (2), overcomes the force of spring (4) and moves power piston (1) outward. This causes the fuel injection pump camshaft to index slightly ahead of the shaft portion (9) of the variable timing unit. Any outward movement of the power piston increases the force on the control valve spring. This tends to reopen the control valve, letting oil escape from the power piston cavity. As oil begins flowing from the cavity again, return spring (4) moves the power piston inward.

1. Power piston. 2. Power piston cavity. 3. Control valve spring. 4. Power piston return spring. 5. Oil inlet passage. 6. Drain port. 7. Control valve. 8. Flyweights. 9. Shaft assembly.

At any given rpm, a balance is reached between the flyweight force and the control valve spring force. The resultant position of control valve (7) will tend to maintain proper pressure behind the power piston. The greater the rpm, the smaller the drain port opening, and the further outward the power piston is forced.

As the power piston is moved outward, the angular relationship of the ends of the drive unit change. As the power piston moves forward in the internal helical spline, the fuel injection pump timing advances.

The gear teeth on shaft assembly (9) drive the governor drive pinion.

Hydra-Mechanical Governor

The governor controls engine speed by balancing governor spring force with governor weight centrifugal force. The compressed governor spring force is applied to increase the supply of fuel to the engine, while the centrifugal force of the engine driven governor weights is applied to decrease fuel to the engine.

1. Shutoff shaft. 2. Collar. 3. Adjusting screw. 4. Stop bar. 5. Lever assembly. 6. Seat assembly. 7. Governor spring. 8. Valve. 9. Weight assembly. 10. Seat. 11. Oil passage. 12. Cylinder. 13. Piston. 14. Sleeve. 15. Oil pump gear. 16. Governor drive housing. 17. Oil pump cover. 18. Pin assembly. 19. Shaft assembly. 20. Lever. 21. Fuel rack. 22. Drive pinion.

Oil pump gear (15), driven by shaft (19), provides immediate pressure oil for the servo portion of the governor. A sump in governor drive housing (16) provides an immediate oil supply for governor operation. A bypass valve in the governor drive housing maintains correct oil pressure.

When the engine is operating, the balance between the centrifugal force of revolving weights (9) and the force of spring (7) controls valve (8). The valve directs pressure oil to either side of rack-positioning piston (13). Depending on the position of the valve (8), piston (13) will move the rack to increase or decrease fuel to the engine to compensate for load variation.

Pressurized lubrication oil, directed through passages in governor drive housing (16) and oil pump cover (17) enters a passage in governor cylinder (12). The oil encircles sleeve (14) within the cylinder. Oil is then directed through passage (11) in piston (13) where it contacts valve (8).

When engine load increases, engine rpm decreases and revolving weights (9) slow down. The weights move toward each other and allow governor spring (7) to move valve (8) down. As valve (8) moves, an oil passage around valve (8) opens to pressure oil. Oil then flows through passage (11) and fills the chamber behind piston (13). The pressure forces the piston and rack down, increasing the amount of fuel to the engine. Engine rpm increases until the revolving weights rotate fast enough to balance the force of the governor spring.

When engine load decreases, engine rpm increases, revolving weights (9) speed-up, and the toes on the weights move valve (8) up, allowing the oil behind piston (13) to flow through a drain passage opened at the rear of the piston. At the same time, the pressure oil between sleeve (14) and piston (13) forces the piston and rack up, decreasing the amount of fuel to the engine. Engine rpm decreases until the revolving weights balance the force of the governor spring.

When the engine is started, a speed limiter plunger located in the governor housing, restricts the movement of the governor control linkage. When operating oil pressure is reached, the plunger in the speed limiter retracts and the governor control can be moved to the HIGH IDLE position.

Fuel Ratio Control

The fuel ratio control coordinates the movement of the fuel rack with the amount of air available in the inlet manifold. The control keeps the fuel to air ratio more efficient, thus minimizing exhaust smoke.

A manually operated override lever (1) is provided to allow unrestricted rack movement during cold starts. After the engine starts, the override automatically resets in the RUN position.

Bolt and collar (8) mechanically connect to the fuel rack. The head of bolt assembly (7) latches through a slot in hook (6) attached to bolt and collar (8). An air line joins the chamber above diaphragm (5), with the air in the engine inlet manifold.

1. Lever. 2. Housing. 3. Spring. 4. Spring. 5. Diaphragm. 6. Hook. 7. Bolt assembly. 8. Bolt and collar.

When the operator moves the governor control to increase engine rpm, the fuel rack moves bolt and collar (8) down until hook (6) contacts the head of bolt assembly (7). The bolt assembly restricts the movement of the bolt and collar until spring (3) and a boost of air pressure in housing (2) forces diaphragm (5), spring (4) and bolt assembly (7) to relieve the restriction to bolt and collar (8). This allows the fuel rack to move to increase the fuel as turbocharger air pressure (boost) increases with the increase in engine rpm.

Fuel Ratio Control (Hydraulic Activated)

The hydraulic activated fuel ratio control automatically causes a restriction to the amount of travel of the rack in the "fuel on" direction, until the air pressure in the inlet manifold is high enough to give complete combustion. The fuel ratio control keeps engine performance high so that black exhaust gases are not seen.

1. Valve. 2. Oil inlet passage. 3. Passage for inlet air pressure. 4. Oil outlet passage. 5. Large oil passage. 6. Oil drain. 7. Spring. 8. Diaphragm. 9. Valve.

The hydraulic activated fuel ratio control has two valves (1) and (9). Engine oil pressure works against valve (1) to control the movement of the fuel rack. Air pressure from the inlet manifold works against diaphragm (8) to move valve (9) to control oil pressure against valve (1).

When the engine is stopped, there is no pressure on either valve. Spring (7) moves both valves to the ends of their travel. In this position, the fuel rack travel is not restricted. Also in this position, an oil outlet passage (4) is open to let oil away from valve (1).

When the engine is started, the open oil outlet passage (4) prevents oil pressure against valve (1) until air pressure from the inlet manifold is high enough to move valve (9) to close the large oil passage (5). Engine oil pressure then works against valve (1) to move this valve into its operating position. The control will operate until the engine is stopped.

When the governor control is moved toward the full load position with the engine running, the head on the stem of valve (1) will cause a restriction to the travel of the fuel rack, until the air pressure in the inlet manifold has an increase. As there is an increase in the air pressure in the inlet manifold, this pressure works against diaphragm (8) to cause valve (9) to move to the left. The large oil passage (5) becomes open to let oil pressure away from valve (1), toward spring (7), and out to drain (6). As there is a decrease in oil pressure, valve (1) moves to the left to let the fuel rack open at a rate equal to (the same as) the air available for combustion.

Air Induction And Exhaust

1. Left side exhaust manifold. 2. Aftercoolers. 3. Right side exhaust manifold. 4. Equalizer tube. 5. Left side air cleaner. 6. Turbocharger. 7. Exhaust outlet. 8. Turbocharger. 9. Right side air cleaner.

The air induction and exhaust system includes two turbochargers (6 and 8) located at the rear of the engine.

Each turbocharger is driven from, and charges, its own cylinder bank. Balanced inlet manifold pressures between banks are assured through an equalizer tube (4) connecting the two aftercooler housings.

Exhaust manifolds (1 and 3) for the Industrial Engine have one section to a cylinder. These are interchangeable between banks. High-temperature studs and nuts are used to secure the manifold sections to the cylinder heads.

Exhaust manifolds (1 and 3) on the Marine Engine are one piece and water-cooled. The water-cooled, one piece manifold, for each cylinder bank helps to insure exhaust gas sealing.

The aftercooler housings (2) are located directly on top of the "V" side of the cylinder heads. The aftercooler housings contain the aftercooler cores, with provision for either engine coolant water or sea water as a cooling medium for the inlet air. The air inlet section of the aftercooler housing is connected to the turbochargers (6 and 8).

Inlet air for the engine is drawn through air cleaners (5 and 9) and directed to the turbochargers. From turbochargers (6 and 8), air is forced directly through the cores of aftercoolers (2) and into the combustion area.

There are four in-head valves (two intake and two exhaust) for each cylinder. The valves are actuated by overhead camshafts and forked rocker arm assemblies, located in the housing on top of the cylinder heads.

Exhaust gases leave each cylinder through two exhaust valve ports. After passing through the turbine side of the turbochargers, the exhaust exits through exhaust outlet (7) located between the turbochargers.


The turbochargers are supported by brackets mounted to the engine cylinder block. All the exhaust gases from the diesel engine pass through the turbochargers.

TURBOCHARGER (Typical Illustration)
1. Air inlet. 2. Compressor housing. 3. Nut. 4. Compressor wheel. 5. Thrust plate. 6. Center housing. 7. Lubrication inlet port. 8. Shroud. 9. Turbine wheel and shaft. 10. Turbine housing. 11. Exhaust outlet. 12. Spacer. 13. Ring. 14. Seal. 15. Collar. 16. Lubrication outlet port. 17. Ring. 18. Bearing. 19. Ring.

The exhaust gases enter the turbine housing (10) and are directed through the blades of a turbine wheel (9), causing the turbine wheel and a compressor wheel (4) to rotate.

Filtered air from the air cleaners is drawn through the compressor housing air inlet (1) by the rotating compressor wheel. The air is compressed by action of the compressor wheel and forced 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 causing the turbocharger turbine wheel and compressor impeller to rotate 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; hence more horsepower derived 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.

------ WARNING! ------

If the high idle rpm or the rack setting is higher than given in the book RACK SETTING INFORMATION (for the height above sea level at which the engine is operated), there can be damage to engine or turbocharger parts.


The bearings for the turbocharger use engine oil under pressure for lubrication. The oil comes in through the oil inlet port (7) and goes through passages in the center section for lubrication of the bearings. Oil from the turbocharger goes out through the oil outlet port (16) in the bottom of the center section and goes back to the engine lubricating system.

The fuel rack adjustment is done at the factory for a specific engine application. The governor housing and turbocharger are sealed to prevent changes in the adjustment of the rack and the high idle speed setting.

Cylinder Heads, Valves And Camshafts

Cylinder Heads and Valves

This is a four stroke cycle engine; i.e., four separate piston strokes are required to complete the firing of one cylinder.

There are four in-head valves for each cylinder; two intake valves and two exhaust valves.

The in-head valves are perpendicular to the bottom face of the cylinder head. The exhaust valves and ports are located toward the outside of the engine. The intake valves are on the inside, toward the vee.

A primary feature of the cylinder head is parallel porting. This provides individual porting for each of the two exhaust valves and the two intake valves. This permits unrestricted flow of air and exhaust gasses; resulting in maximum breathing capability and efficiency.

Valves, valve seats, seating springs and rotators are all part of the cylinder head assembly. The valve seats are pressed into the cylinder head and are replaceable.

Valve rotators add much to valve life. Each valve is rotated three degrees on every lift; thus minimizing pitting of the valve faces and valve seats. The rotation also causes a wiping action to remove carbon deposits from the valve seat.

Rocker Arms

Valve action is accomplished through a roller-rocker arm arrangement. The forked rocker arm (2), located in the camshaft housing, pivots on a shaft (4) at one end and depresses two valves at the other end through adjusting screws. A roller (5), supported by a pin near the center of the rocker arm, rides on the camshaft (1) lobe. Thus, one camshaft lobe actuates the forked rocker arm and opens two valves simultaneously.

1. Camshaft. 2. Rocker arm. 3. Adjusting screw. 4. Pivot shaft. 5. Roller. 6. Spring. 7. Valve.

Valve adjustment can be quickly and accurately accomplished with a screwdriver. No thickness gauge is required. Turn the adjusting screw (3) down to remove all clearance, then back off to the required setting.


This engine uses two overhead camshafts in each cylinder bank. The inner camshaft in each bank actuates all the intake valves and the other camshaft actuates all the exhaust valves.

The camshafts are driven from both ends of the engine. The right bank camshafts are driven by the rear gear train. On the left bank, the inlet camshaft drives the exhaust camshaft. On the right bank, the exhaust camshaft (F) drives the inlet camshaft (E).

A. Flywheel end. B. Left side. C. Front end. D. Right side. E. Inlet camshaft. F. Exhaust camshaft.

The camshaft journals are supported in integrally cast webs of the camshaft housings. Pressure lubrication to the camshaft journals is supplied from the cylinder block through the cylinder head, and into drilled passages in the camshaft housing.

A crankcase breather is mounted on the front of the right bank camshaft cover. The element is removable for cleaning. A fumes disposal tube carries the crankcase fumes to a level below the engine.

Lubrication System

1. Strainer. 2. Prelube pump. 3. Check valve. 4. Oil filter housing. 5. Oil supply to left rear valve train. 6. Oil supply to piston cooling jets. 7. Oil supply to left front valve train. 8. Turbocharger oil supply line. 9. Oil supply to front timing gears. 10. Oil supply to governor. 11. Oil supply to oil pressure switch. 12. Oil supply to rear timing gears. 13. Oil supply to right rear valve train. 14. Oil supply to right front valve train. 15. Turbocharger oil supply line. 16. Oil filter bypass valve. 17. Oil supply to piston cooling jets. 18. Engine oil pump. 19. Oil pump bypass valve. 20. Oil cooler. 21. Oil cooler bypass valve.

When the start switch is turned to the START position, prelube pump (2) ensures that adequate oil pressure is available for the engine components and turbocharger bearings before the starting motors are activated. An oil passage leads from the prelube pump directly to the oil filters. When oil pressure in the engine is adequate, a pressure sensitive switch closes, thus energizing the starting motor circuit. The prelube pump shuts off when the start switch is released.

The lubrication system has a gear driven oil pump (18) located at the bottom of the cylinder block within the oil pan. A bypass valve (19) located in the oil pump body limits the maximum oil pressure from the pump. This pump is gear driven through an idler off the rear timing gears. The drive gear is baffled to reduce aeration of the oil in the oil pan.

Oil from the pump is directed through a passage in the cylinder block and then through an external oil line to oil cooler (20). An oil cooler bypass valve (21) and line is provided to bypass cool oil around the cooler. The increased pressure of cool oil causes the bypass valve to open and permit oil flow directly from the pump to the filters. When the oil temperature increases, the pressure returns to normal and the bypass valve closes, allowing the oil to flow through the cooler before going to the filters.

An external line directs the flow from oil cooler (20) to the oil filter housing (4), located at the front of the engine, just below the fuel filter housing. A bypass valve (16), located in the inlet of the oil filter housing, allows oil to bypass the oil filter elements in the event they become restricted.

From the oil filters, oil is directed to the main oil manifold. This manifold is a passage extending the entire length of the cylinder block just below the "V". From this manifold, branch passages supply lubricating oil to the front and rear timing gears, right and left bank valve mechanisms, main and connecting rod bearings, piston cooling jets, and the governor and fuel injection pump housing.

The governor and fuel injection pump lubrication system includes an oil pump within the governor. Oil that drains from the speed limiter collects in the governor housing. This reservoir supplies oil to the governor oil pump located in the governor drive housing. The governor oil pump also supplies pressure oil to the servo to obtain immediate governor response during starting.

The fuel injection pump housing contains an oil manifold that supplies oil to the camshaft bearings and the lifter rollers. The lifter rollers and camshaft lobes are lubricated each time the individual lifters move up and uncover an oil hole. Lubricant drains from the fuel pump housing back to the cylinder block.

Cooling System

Engine Coolant

1. Left bank cylinder heads. 2. Left bank cylinders aftercooler. 3. Water temperature regulator housing. 4. Heat shield. 5. Right bank cylinders aftercooler. 6. Water pump. 7. Oil cooler. 8. Right bank cylinder heads. 9. Coolant bypass line. 10. Radiator.

Coolant is circulated by a water pump (6) located on the right front side of the flywheel housing. This pump is driven from the rear timing gear train.

Coolant from the radiator (10) or heat exchanger flows to the water pump. The entire pump flow is directed through the engine oil cooler (7) and the bypass tube on the right side of the engine. At the outlet of the oil cooler, part of the coolant is directed to the right bank cylinders (8), while the remaining flow continues to a lower chamber in the regulator housing (3), located at the front of the engine.

The lower portion of the regulator housing divides the flow equally between the left bank cylinders (1) and the aftercoolers (2 and 5) incorporated in the inlet manifolds. Flow exits from the rear of the aftercoolers into a heat shield (4). From here, the flow is divided to enter the cylinder block at the bottom rear of each cylinder bank. Coolant circulates up to the cylinder heads and exits to the regulator housing. Four water temperature regulators control the division of flow to the cooling unit (radiator, heat exchanger, or cooling tower) or back to the water pump inlet.

Until the coolant reaches operating temperature, the regulators will remain closed and bypass the coolant flow through line (9) to the water pump inlet. When the operating temperature reaches 175° F (79.4° C) the regulators begin to open and allow some coolant to flow to the cooling unit. The regulators are at full open position at the normal operating temperature of 197° F (92° C). This modulating bypass arrangement provides full coolant flow during engine warm-up, resulting in more uniform temperatures throughout the engine.

Marine Engine Equipped For Auxiliary Water Aftercooling

1. Turbocharger heat shield. 2. Left bank cylinder head. 3. Left bank cylinders aftercooler. 4. Water cooled exhaust manifold. 5. Heat exchanger. 6. Expansion tank. 7. Right bank cylinders aftercooler. 8. Marine gear oil cooler. 9. Auxiliary water pump. 10. Diesel engine water pump. 11. Right bank cylinder head. 12. Engine oil cooler. 13. Water cooled exhaust manifold.

Auxiliary water, from its source, is supplied to the auxiliary water pump (9). The auxiliary water pump is located at the right rear of the flywheel housing and is driven by the same gear that drives the diesel engine water pump (10). From the auxiliary water pump, part of the coolant flows to the marine gear oil cooler (8) (if so equipped), and then to the rear of the aftercoolers (3 and 7). Coolant flow through the aftercoolers is rear-to-front and then to a heat exchanger or to waste.

If an engine is equipped with water-cooled exhaust manifolds (4 and 13) and a turbocharger heat shield (1), these items are connected to the engine cooling system as illustrated.

Engine coolant temperature is controlled by the use of water temperature regulators. On cold starts, the regulators are closed, causing cold water from the engine to be circulated through the expansion tank (6) to the engine water pump inlet. Water from the heat exchanger (5) cannot enter the system because the regulators block the return flow.

As coolant temperature rises, the regulators open slightly to allow heat exchanger water to flow to the expansion tank where it mixes with heated water from the engine.

Basic Engine Components

Cylinder Block

A. Flywheel end. B. Left side. C. Front end. D. Right side.

The cylinder block is a 60° vee. One bank of cylinders is offset from the other bank of cylinders. This offset provides space at each end of the cylinder block for the camshaft drives. The offset also allows two connecting rods to be secured to each connecting rod journal of the crankshaft.

Cylinder Liners

On earlier engines a steel spacer plate is used between the cylinder heads and the cylinder block. The cylinder liners are supported in counterbores in the spacer plate.

On later engines the cylinder liner 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 cylinder liner and the cylinder block.

Pistons, Rings And Connecting Rods

The piston has three rings; two compression rings 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 integrally in the piston. The oil ring is spring loaded. Holes in the oil ring groove provide for the return of oil to the crankcase.

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

A steel heat plug, in the crater of the piston, protects the top of the piston from erosion and burning at the point of highest heat concentration.

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

The connecting rods have diagonally cut serrated joints which allow removal of the piston and connecting rod assembly upward through the cylinder liner. Earlier engines use the same part number connecting rod for both odd and even numbered cylinders. This connecting rod uses a locating tab to position the connecting rod bearing.

Connecting rod bearings in later engines do not have locating tabs but are positioned by dowels in the connecting rods. The rods with dowel located bearings are marked " Even Cyl Only..." or " Odd Cyl Only...". These rods must be installed in the correct bank. They may be installed in earlier engines if the correct piston cooling jets are installed. Refer to Special Instruction (GEG02495) for complete instructions.


The crankshaft transforms the combustion forces in the cylinders into usable rotating torque which powers the machine. There is a timing gear at each end of the crankshaft which drives the respective timing gears.

Interconnecting drilled passages supply pressurized lubricating oil to all bearing surfaces on the crankshaft.

Electrical System

The electrical system is a combination of two separate electric circuits: the charging circuit and starting circuit. Each circuit is dependent on some of the same components. The battery (batteries), disconnect switch, circuit breaker, cables and wires from the battery are, usually common in each of the circuits.


The disconnect switch must be ON to allow the electrical system to function. Some charging circuit components will be damaged if the engine is operated with the disconnect switch OFF.

The charging circuit is in operation when the diesel engine is operating. The electricity producing (charging) unit is an alternator. A regulator in the circuit senses the state of charge in the battery and regulates the charging unit output to keep the battery fully charged.

The starting circuit operates only when the disconnect switch is ON and the start switch is actuated.

The diesel engine starting circuit includes a glow plug for each diesel engine cylinder. Glow plugs are small heating elements in the precombustion chamber which promote fuel ignition when the engine is started in low temperatures.

The load and charging circuits are both connected on the same side of the ammeter while the starting circuit connects to the other side of the ammeter.

System Components

Starter Solenoid

A solenoid is a magnetic switch that utilizes low current to close a high current circuit. The solenoid has an electromagnet with a movable core (6). There are contacts (4) on the end of the core. The contacts are held open by a spring (5) that pushes the core away from the magnetic center of the coil. Low current will energize the coil and form a magnetic field. The magnetic field draws the core to the center of the coil and the contacts close.

1. Coil. 2. Switch terminal. 3. Battery terminal. 4. Contacts. 5. Spring. 6. Core. 7. Component terminal.

Starting Motor

1. Field. 2. Solenoid. 3. Clutch. 4. Pinion. 5. Commutator. 6. Brush assembly. 7. Armature.

Two starting motors are used to turn the engine flywheel fast enough to get the engine running.

When the heat start switch is in the Start position a low current from the switch actuates two magnetic switches (relays) which are wired in parallel. Each relay completes a higher current circuit to a solenoid on a starter motor. This current causes the solenoid to move the pinion into engagement with the ring gear on the flywheel of the engine. After the pinion is engaged the electrical contacts in the solenoid close the circuit between the battery and the starting motor. When the switch is disengaged the relay opens the circuit to the solenoid. The starting motor stops and the pinion moves away from the flywheel.

When the heat start switch is in the Heat position, a low current from the switch actuates the magnetic switch (relay). The relay completes a higher current circuit to the glow plugs. When the switch is disengaged, the relay opens the higher current circuit.

Alternator (Delco-Remy) 1N9406

This alternator is a belt driven, three phase, self-rectifying, brushless charging unit with a built in voltage regulator.

The only moving part in the alternator is the rotor (4) which is mounted on a ball bearing (6) at the drive end, and a roller bearing (3) at the rectifier end.

1. Regulator. 2. Fan. 3. Roller bearing. 4. Rotor. 5. Stator windings. 6. Ball bearing.

The regulator is enclosed in a sealed compartment. It senses the charge condition of the battery, the electrical system power demands and controls the alternator output accordingly.

Wiring Diagrams

The following diagrams illustrate an electrical system with glow plugs and a system without glow plugs. Glow plugs are an aid to starting in low temperature. A HEAT-START switch is included in the glow plug circuit. Starting systems without glow plugs use a push button switch with two post connections to energize the starting circuit.

Both electrical systems incorporate a prelube pump within the system. The oil pressure switch will activate the starting circuit after the prelube pump has provided sufficient oil pressure to the engine components and turbocharger bearings.

Negative Ground System

This system is most often used in applications where no special precautions are necessary to prevent local radio interference and/or electrolysis of grounded components.



Insulated Ground Systems

This system is most often used in applications where radio interference is undesirable or where conditions are such that grounded components would corrode from electrolysis.


Safety Shutoff Control

A combined overspeed and low oil pressure safety shutoff is provided for industrial engines. Marine engines are equipped with reversal protection in addition to overspeed. The overspeed and reversal protection controls do not have protection for low oil pressure.

Safety shutoff (1) is mounted in the V of the engine at the front of the fuel pump housing. The overspeed portion is driven by the fuel injection pump camshaft.

NOTE: In cold weather operation, it may be necessary to push the reset button (4) while cranking the diesel engine to prevent activating the shutoff control. This is necessary as the oil pressure will not increase to the operating range fast enough because of the longer cranking period needed under these conditions.

Under conditions of normal operation, pressure of lubricating oil will increase to the operating range before the follower has moved to the limit of travel and activates the release latch and rod.

Engine lubricating oil pressure is used to actuate the shutoff control. Line (3) provides for a connection of oil pressure to a water temperature shutoff control valve. Line (2) supplies oil pressure to the shutoff control.

1. Safety shutoff control. 2. Pressure oil line to shutoff control. 3. Pressure oil connection to water temperature shutoff. 4. Reset button. 5. Emergency manual shutoff button. 6. Fuel rack shutoff cable.

Emergency manual shutoff button (5) works in conjunction with the overspeed shutoff and provides the operator with an emergency shutoff.

Reset button (4) is used to reset the control after the engine has been stopped by the control.

NOTE: It is usually not necessary to reset the control after a normal shutdown.

Overspeed Shutoff

Should an overspeeding condition occur, the overspeed shutoff control, located in the shutoff control housing, will actuate the release rod and then the fuel rack shutoff.

Overspeed carrier assembly (1) is driven by the fuel pump camshaft. Within the carrier flange is rotating weight (2), held toward the center of the carrier shaft by an adjusting screw, spring and nut.

As engine rpm increases, the centrifugal force acting on the weight increases, and the weight moves out of the carrier flange. This movement of the weight continues until the spring force (tending to hold the weight in) is equal to the centrifugal force (tending to throw the weight out).

1. Carrier assembly. 2. Rotating weight. 3. Release lever. 4. Release rod.

When the engine overspeeds, the increased centrifugal force of the weight moves the weight out of the rotating carrier flange. The weight now unlatches lever (3) and spring force moves rod (4) to actuate the shutoff linkage which stops the engine.

Water Temperature Shutoff Control Valve Operation

The water temperature shutoff in itself is a control valve for the oil pressure shutoff. It is actually the oil pressure shutoff that functions to stop the engine.

1. Spring. 2. Inlet port. 3. Stem. 4. Thermostat assembly. 5. Ball. 6. Outlet port.

Thermostat assembly (4) is immersed in engine coolant. When the water temperature is normal, spring (1) holds ball (5) on its seat which blocks the oil flow. This allows oil pressure to build up in the safety shutoff system. Abnormally high engine water temperature causes the thermostat assembly to expand against the stem (3) which unseats the ball (5). This allows oil held under pressure in the safety shutoff control system to return to the engine crankcase through the outlet port (6). The resultant drop in pressure causes the oil pressure shutoff to shut down the engine.

Low Oil Pressure Shutoff And Water Temperature Shutoff

The oil pressure control will stop the engine should lubricating oil pressure drop below the safe operating range, or if an overheating condition occurs. Excessively hot water opens a shutoff control valve, simulating low oil pressure.

Under normal operating conditions, engine lubricating oil is directed through the pressure oil line to cover (4). The oil is then directed against control piston (6).

One end of worm follower (2) is piloted into guide (5). The follower is free to pivot on shaft (3) in the housing, and is actuated by the movement of guide (5).

Worm shaft (1) is driven by the fuel pump camshaft and rotates at one-half engine speed.

When engine oil pressure is within the safe operating range, piston (6) is held against guide (5), compressing spring (7) and pivoting follower (2) out of mesh with worm shaft (1).

1. Worm shaft. 2. Follower. 3. Follower shaft. 4. Cover. 5. Guide. 6. Piston. 7. Spring. 8. Release rod.

1. Worm shaft. 2. Follower. 3. Follower shaft. 5. Guide. 8. Release rod. 9. Pin. 10. Release lever. 11. Spring.

Should lubricating oil pressure drop below normal operating range, oil pressure actuating piston (6) will also drop. Spring (7) will force guide (5) back, moving piston (6) to the rear of its chamber, causing follower (2) to pivot on shaft (3) and mesh with worm shaft (1).

1. Worm shaft. 2. Follower. 8. Release rod. 9. Pin. 10. Release lever. 11. Spring.

12. Fuel rack shutoff cable. 13. Lever assembly. 14. Fuel rack.

With follower (2) meshed with worm shaft (1), the follower will travel the length of worm shaft (1) which is turning at one-half engine speed. As the follower reaches the end of its travel, pin (9) on the follower makes contact with release lever (10). The release lever is then tripped and rod (8) is forced to shutoff position by the force of spring (11).

Release rod (8) moves cable (12) and lever (13), forcing fuel rack (14) to shutoff position.

Emergency Manual Shutoff Button

Emergency shutoff button (5) is never used for normal shutdown. Under normal conditions, all load would be first removed from the engine and engine rpm lowered to low idle before the engine is shut down.

If an emergency situation is encountered where the engine must be shut down immediately, push and hold button (5) in until the release lever rod has been released.

Pushing on button (5) moves plunger (4) against pin (3). The pin forces spring loaded weight (1) out of carrier assembly (2), creating the same condition as overspeeding.

1. Weight. 2. Carrier assembly. 3. Pin. 4. Plunger. 5. Button.

Resetting The Control

Whenever the engine has been shut down by the safety shutoff control, the reason for the shutdown must be found and corrected. The control must be reset before the engine can be started.

Overspeed or Emergency Shutdown Control Reset

Move lever (1) to reset the shutoff control after either an overspeed shutdown or an emergency manual shutdown. The engine can now be started.

1. Lever.

Low Oil Pressure, Water Temperature Shutdown Control Reset

Depress reset button (4), located on the top of the shutoff control housing, to manually move piston (3) against follower guide (1). The movement of the guide pivots worm follower (2) away from the worm shaft to allow the spring to return the follower to the start of the worm shaft thread.

Latch the spring loaded release rod (5) by pulling on the overspeed shutdown reset lever.

1. Follower guide. 2. Follower. 3. Piston. 4. Reset button. 5. Release rod.

The engine can now be started.

NOTE: In cold weather operation it may be necessary to push the reset button, while cranking the diesel engine, before the engine starts.

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