Introduction

NOTE: For Specifications with illustrations, make reference to SPECIFICATIONS for D379B, D398B, D399 GENERATOR SET ENGINES, Form No. SENR2175. If the Specifications in Form SENR2175 are not the same as in the Systems Operation and the Testing and Adjusting, look at the printing date on the back cover of each book. Use the Specifications given in the book with the latest date.

Fuel System

SCHEMATIC OF FUEL SYSTEM
1. Fuel transfer pump inlet line. 2. Fuel priming pump. 3. Fuel passage. 4. Inlet from tank. 5. Fuel return line. 6. Fuel tank. 7. Fuel transfer pump outlet line. 8. Fuel transfer pump. 9. Fuel filter housing. 10. Fuel injection pump housing.

There is one fuel injection pump and one fuel injection valve for each cylinder. The fuel injection pumps are located in the fuel injection pump housing in the Vee of the engine. The fuel injection valves are located in the precombustion chambers in the cylinder heads.

Fuel transfer pump (8) is located on the front, right hand side of the accessory drive housing. The pump is driven from the front of the oil pump drive gear.

When the engine is running, fuel is pulled from fuel tank (6) through fuel transfer pump inlet line (1) by fuel transfer pump (8). The fuel is then pushed to fuel filter housing (9). Only the fuel needed goes through the fuel filters. The extra fuel goes to fuel control valve (14). The fuel from the fuel filters goes to the fuel injection pump housing (10). A passage in the housing gives fuel to each fuel injection pump. Individual fuel lines carry fuel from the fuel injection pumps to each cylinder.

FUEL FLOW THROUGH FUEL CONTROL VALVE (ENGINE RUNNING)
1. Fuel transfer pump inlet line. 2. Fuel priming pump. 4. Inlet from tank. 7. Fuel transfer pump outlet line. 9. Fuel filter housing. 11. Outlet passage. 12. Orifice. 13. Fuel passage. 14. Fuel control valve.

Fuel control valve (14) controls the pressure of the fuel in the fuel system. When the fuel system is at maximum pressure, fuel control valve (14) moves and the extra fuel not needed by the engine is bypassed back to the inlet side of the fuel transfer pump. Any air in the fuel filter housing escapes through orifice (12) and outlet passage (11) into the fuel return line to fuel tank.

Fuel priming pump (2) is located on the top of the fuel filter housing. The fuel priming pump is used to vent air from the fuel system and fill the fuel filter housing with fuel after the filters have been changed.

SUCTION STROKE OF PRIMING PUMP
1. Fuel transfer pump inlet line. 2. Fuel priming pump. 3. Fuel passage. 4. Inlet from tank. 7. Fuel transfer pump outlet line. 9. Fuel filter housing.

PRESSURE STROKE OF PRIMING PUMP
1. Fuel transfer pump inlet line. 2. Fuel priming pump. 4. Inlet from tank. 7. Fuel transfer pump outlet line. 9. Fuel filter housing. 11. Outlet passage. 12. Orifice. 13. Fuel passage. 14. Fuel control valve.

When the handle of the fuel priming pump is pulled out (suction stroke), fuel is pulled through fuel passage (3) past the check valve in the inlet side of the pump and into the fuel priming pump.

When the handle of the pump is pushed in (pressure stroke), the fuel in the pump is pushed through the check valve on the outlet side of the pump and into the fuel filter housing through fuel passage (13). Air in the filter housing and some fuel escapes through orifice (12) and outlet passage (11) back to fuel tank (6) through fuel return line (5). There is a sight gauge in return line (5) and when there are no air bubbles in the fuel returning to the fuel tank, all of the air has been removed from the system.

Duplex Fuel Filter System

The duplex fuel filter system makes it possible to change elements for the fuel filters while the engine is running at any speed.

During normal operation, the selector lever (1) should be in the "Main Filter Run-Aux. Off" position. The fuel then will be cleaned by the elements of the main filter which are located in the right side of the filter housing. The two elements of the auxiliary filter are located in the left side of the housing.

DUPLEX FUEL FILTER
1. Selector lever. 2. Priming pump.

When the gauge for fuel pressure shows indication of minimum pressure of 20 psi (140 kPa) the main elements must be changed. While the main elements are being changed, the fuel must be cleaned by the two elements of the auxiliary filter.

Explanation of flow, with the engine running, for the selector lever positions is as follows:

Aux. Vent-Main Run

Any air in the auxiliary filter will go back to the fuel tank while the main filters will filter the diesel fuel.

Aux. Filter Run-Main Off

The auxiliary elements now filter the diesel fuel instead of the main elements.

Main Vent-Aux. Run

While the auxiliary elements filter the fuel, the main filter housing will fill with fuel.

Main Filter Run-Aux. Off

The main filters will now be filtering the fuel.

Both Filters Run

This will permit more running time when both filter systems are almost to a condition of restriction as shown by the fuel pressure gauge.

Fuel Injection Pumps

FUEL INJECTION PUMP
1. Pump. 2. Inlet port. 3. Pump plunger. 4. Gear segment. 5. Fuel rack. 6. Fuel passage. 7. Lifter. 8. Camshaft.

Fuel enters the fuel injection pump housing through fuel passage (6) and enters the fuel injection pump body through inlet port (2). Pump plunger (3) and lifter (7) are lifted by lobes on camshaft (8) and always make a full stroke. Each pump measures the amount of fuel to be injected into its respective cylinder and forces the fuel out the fuel injection valve.

The quantity of fuel sent to the fuel injection valve is changed by the rotation of the pump plunger in the barrel. The pump plunger is turned by the governor action through fuel rack (5). The fuel rack turns gear segment (4) on the bottom of the pump plunger.

Fuel Injection Valve

FUEL INJECTION VALVE CROSS SECTION
1. Fuel injection line. 2. Nut. 3. Body. 4. Nozzle assembly.

High pressure fuel from the fuel injection pumps is moved through the fuel injection lines to the fuel injection valves. As high pressure fuel enters the nozzle assembly, the check valve in the nozzle opens and permits the fuel to enter the precombustion chamber. The fuel injection valve gives the correct characteristics (spray pattern) for good fuel combustion.

Woodward UG8 Dial Governor

SCHEMATIC OF UG8 DIAL GOVERNOR

The UG8 Dial Governor is a mechanical-hydraulic governor. A hydraulic activated power piston is used to turn the output terminal shaft of the governor. A lever on the terminal shaft is connected to the fuel rack by a linkage rod. The governor has a separate oil supply and oil pump. The governor oil pump and ballhead are driven from a shaft in the governor drive housing. The shaft is driven by the fuel pump drive shaft.

The oil pump gives pressure oil to operate the power piston. The drive gear of the oil pump has a bushing in which the pilot valve plunger moves up and down. The driven gear of the oil pump is also the drive for the ballhead.

An accumulator is used to keep a constant oil pressure of approximately 120 psi (830 kPa) to the top of the power piston and to the pilot valve.

The power piston is connected by a lever to the output terminal shaft. There is oil pressure on both the top and bottom of the power piston. The bottom of the piston has a larger area than the top.

Less oil pressure is required on the bottom than on the top to keep the piston stationary. When the oil pressure is the same on the top and bottom of the piston, the piston will move up and cause the output terminal shaft to turn in the increase fuel direction. When oil pressure on the bottom of the piston is directed to the sump, the piston will move down and cause the output terminal shaft to turn in the decrease fuel direction. Oil to or from the bottom of the power piston is controlled by the pilot valve.

The pilot valve has a pilot valve plunger and a bushing. The bushing is turned by the governor drive shaft. The rotation of the bushing helps reduce friction between the bushing and the plunger. The pilot valve plunger has a land that controls oil flow through the ports in the bushing. When the pilot valve plunger is moved down, high pressure oil goes to the bottom of the power piston and the power piston will move up. When the pilot valve plunger is moved up, the oil on the bottom of the power piston is released to the sump and the power piston moves down. When the pilot valve plunger is in the center (balance) position, the oil port to the bottom of the power piston is closed and the power piston will not move. The pilot valve plunger is moved by the ballhead assembly.

The ballhead assembly has a ballhead, flyweights, speeder spring, thrust bearing, speeder plug, and speeder rod. The ballhead assembly is driven by a gear and shaft from the driven gear of the oil pump. The speeder rod is fastened to the thrust bearing which is on the toes of the flyweights. The speeder rod is connected to the pilot valve plunger with a lever. The speeder spring is held in position on the thrust bearing by the speeder plug.

As the ballhead turns, the flyweights move out due to centrifugal force. This will make the flyweight toes move up and cause compression of the speeder spring. When the force of the speeder spring and the force of the flyweights are equal the engine speed is constant. The speeder plug can be moved up or down manually to change the compression of the speeder spring and will change the speed of the engine.

The compensation system gives stability to engine speed changes. The compensation system has a needle valve and two pistons - an actuating piston and a receiving piston. The actuating piston is connected to the output terminal shaft by the compensation adjusting lever. A fulcrum that is adjustable is on the lever. When the position of the fulcrum is changed, the amount of movement possible of the actuating piston is changed.

The receiving piston is connected to the pilot valve plunger and the speeder rod by a lever.

The needle valve makes a restriction to oil flow between the oil sump and the two pistons.

When the actuating piston moves down, the piston forces the oil under the receiving piston and moves it up. When the receiving piston moves up it raises the pilot valve plunger to stop the flow of oil to the bottom of the power piston.

When the engine is in operation at a steady speed the land on the pilot control valve is in the center of the control port of the bushing. A decrease in load will cause an increase in engine speed. With an increase in engine speed the flyweights move out and raise the speeder rod and floating lever. This raises the pilot valve plunger and releases oil from the bottom of the power piston. As the power piston moves down the output terminal shaft moves in the decrease fuel direction. When the output terminal shaft moves, the actuating compensation piston moves up and causes a suction on the receiving piston which moves down. The floating lever is pulled down by the receiving piston and the lever moves the pilot control valve down to close the control port. The output terminal shaft and power piston movement is stopped. As the engine speed returns to normal the flyweights move in and the speeder rod moves down. When the oil pressure in the compensation system and the sump oil become the same through the needle valve, the receiving compensation piston moves up at the same rate as the speeder rod moves down. This action keeps the pilot valve plunger in position to close the port.

An increase in load will cause a decrease in engine speed. When engine speed decreases, the flyweights move in and lower the speeder rod and floating lever. This lowers the pilot valve plunger and lets pressure oil go under the power piston. The power piston moves up and turns the output terminal shaft in the increase fuel direction. When the output terminal shaft moves, the actuating compensation piston moves down and causes a pressure on the receiving piston which moves up. The floating lever is pushed up by the receiving piston and the lever moves the pilot valve plunger up to close the control port. The output terminal shaft and power piston movement is stopped.

A change to the speed setting of the governor will give the same governor movements as an increase or decrease in load.

The synchronizer is used to change engine speed. The speed setting motor on the top of the governor can also be used to change engine speed. Either control turns the speeder plug which moves up or down and changes the force of the speeder spring. The synchronizer indicator gives an indication of the number of turns the synchronizer has moved.

The load limit control is used to control the amount of travel of the output terminal shaft. The control can be used to stop the engine if the knob is turned to zero.

The speed droop control is used to adjust the amount of speed droop from zero to one hundred percent. Speed droop is the difference between no load high idle rpm and full load rpm. This difference in rpm divided by the full load rpm and multiplied by 100 is the percent of speed droop.

UG8 DIAL GOVERNOR
1. Speed droop knob. 2. Synchronizer knob. 3. Load limit knob. 4. Synchronizer indicator.

Zero speed droop is used on a single system engine, such as a standby generator set. Speed droop higher than zero permits a load to be divided between two or more engines connected to the same load.

Air Inlet And Exhaust System

AIR INLET AND EXHAUST SYSTEM
1. Exhaust manifolds. 2. Right cylinders. 3. Diffuser plate. 4. Right turbocharger impeller. 5. Exhaust elbow. 6. Left cylinders. 7. Turbocharger turbine wheels. 8. Left turbocharger impeller. 9. Aftercooler.

The air inlet and exhaust system has two turbochargers and an aftercooler (9). The right turbocharger uses exhaust gas from the right side to drive the turbine (7), but gives air to the left cylinders (6). The left turbocharger uses exhaust gas from the left side to drive turbine (7) and gives air to the right cylinders (2).

When the engine load increases, the volume of exhaust gases increase and cause the turbine in the turbocharger to turn faster. This will cause the impeller (4 & 8) to turn faster and increase the inlet manifold air pressure. As the pressure of the air increases, the temperature of the air also increases. An aftercooler is installed between the turbochargers and the inlet manifold to help cool the inlet air.

A diffuser plate (3) in the center of exhaust elbow (5) keeps the exhaust gases from the turbocharger outlets apart to reduce exhaust back pressure.

Aftercooler

The aftercooler is installed on the top of the flywheel housing. The aftercooler has two separate cores, one for each inlet manifold. Air is pushed by the turbocharger into the aftercooler and the air goes around the fins of the aftercooler core. Coolant constantly flows through the tubes in the aftercooler core to remove the heat from the air. The cooler air, which is heavier (more dense), will permit more fuel to burn and give an increase in power.

Valves And Valve Mechanism

The valves and valve mechanism control the flow of inlet air and exhaust gases into and out of the cylinder.

The intake and exhaust valves are opened and closed by movement of these components; crankshaft, camshaft, lifters, push rods, rocker arms, and valve springs.

The gear on the crankshaft is timed to and drives the camshaft gear attached to the camshaft. When the camshaft turns, the lobes on the camshaft cause the valve lifters to move up and down. The valve lifters move the push rods, which move the rocker arms. Movement of the rocker arms causes the intake and exhaust valves to open and close in the firing order (injection sequence) of the engine. Valve springs for each valve close the valve and holds them in the closed position.

VALVE AND VALVE MECHANISM (Cross Section, Single Spring Type)
1. Rocker arm. 2. Locks. 3. Spring. 4. Retainer. 5. Guide. 6. Valve rotator. 7. Push rod. 8. Valve. 9. Bracket assembly. 10. Connector. 11. Valve lifter.

Each valve has a valve rotator under the valve spring. The valve rotator causes the valve to turn approximately three degrees each time the valve opens and closes. This action of the valve keeps carbon deposits off of the valve face and valve seat.

Turbocharger

The turbochargers are installed at the rear of the exhaust manifolds. All of the exhaust gases from the engine go through the turbochargers.

The exhaust gases enter turbine housing (5) and go through the blades of turbine wheel (6), causing the turbine wheel and compressor wheel (1) 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.

CROSS SECTION OF TURBOCHARGER
1. Compressor wheel. 2. Compressor housing. 3. Thrust bearing. 4. Lubrication inlet port. 5. Turbine housing. 6. Turbine wheel. 7. Air inlet. 8. Exhaust outlet. 9. Sleeve. 10. Shaft journal bearings. 11. Sleeve. 12. Exhaust inlet.

When the 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.

The bearings for the turbocharger use engine oil for lubrication. The oil comes in through lubrication inlet passage (4) and goes through passages in the center section for lubrication of the bearings. Oil from the turbocharger goes out through the lubrication outlet passage in the bottom of the center section and goes back to the engine lubrication system.

Lubrication System

SCHEMATIC FLOW DIAGRAM OF THE LUBRICATION SYSTEM (Pressure oil flow is shown in light grey, suction oil, return oil or splash-lubricated points are shown in dark grey)
1. Oil return line for turbocharger. 2. Oil supply line for turbocharger. 3. Oil manifold. 4. Booster oil pump for governor. 5. Valve mechanism. 6. Oil manifold. 7. Oil cooler. 8. Filter housing. 9. Camshaft bearings. 10. Main bearings of crankshaft. 11. Connecting rod bearings. 12. Piston cooling jets. 13. Pump of prelube system. 14. Pressure regulating valve. 15. Suction bell. 16. Single section oil pump. 17. Oil pan base.

The lubrication system uses a single section oil pump to send lubrication oil to the engine components. The 16 cylinder engines have a prelubrication pump in addition to the main oil pump. The prelubrication pump is used to give lubrication to the engine components before the engine is started.

Oil from the oil pan base (17) is pulled through suction bell (15) and pipe to oil pump (16). The oil pump then pushes the oil to oil cooler (7). The pressure regulating valve (14) between the oil pump and the oil cooler controls the maximum pressure of the oil to the engine. Oil from the oil cooler goes to oil filter housing (8). An oil filter relief valve in the oil filter housing controls the flow of oil in the housing. When the oil is cold or the oil filters have a restriction, the relief valve opens and oil flows around the oil filter elements to oil manifold (6). When the oil gets warm, and there is no restriction to the oil filters, the relief valve is closed and oil flows through the oil filters to the oil manifold.

A service indicator for the oil filters is on top of the oil filter housing. When the red indicator button goes up approximately to the center of the clear indicator with the oil warm the oil filter elements must be changed.

Oil from the oil manifold flows through oil passages and lines to the inside and outside components of the engine.

The oil in oil manifold (6) goes to camshaft bearings (9), crankshaft main bearings (10), connecting rod bearings (11), valve mechanism (5), piston cooling jets (12), and to oil manifold (3).

The oil in oil manifold (3) goes to the turbocharger, governor, and fuel injection pump housing. When the engine is equipped with an oil pressure shutoff or reversal protection control, they also get oil from oil manifold (3). On 8 and 12 cylinder engines there is a turbocharger quick lubrication valve that gives immediate pressure oil to the turbochargers at engine start up. Unfiltered oil from the oil cooler goes through an oil line to the turbocharger quick lubrication valve at engine start up. When the oil in oil manifold (3) gets pressure, the lubrication valve shuts off the unfiltered oil and the turbochargers now get filtered oil from oil manifold (3).

The rear timing gear bearings get pressure oil through passages from the rear camshaft and crankshaft bearings. The gears get lubrication from the return oil from the turbochargers.

SCHEMATIC FLOW DIAGRAM OF THE FRONT ACCESSORY DRIVE
6. Oil manifold. 18. Water pump gear. 19. Oil pump gear. 20. Main idler gear. 21. Balancer gear. 22. Crankshaft gear. 23. Idler gear. 24. Idler gear.

The front accessory drive gets pressure oil from oil manifold (6) through a passage from the front crankshaft main bearing. Steel tubes in the front accessory drive housing give oil to all of the bearings for the gears.

Duplex Oil Filter System

The duplex oil filters permit the main oil filters to be changed while the engine is in operation.

The duplex oil filter system has two auxiliary oil filters (5), a filter vent valve (2) and selector valve (1).

The selector valve (1) is used to change the flow of engine oil from the main oil filters (3) to the auxiliary oil filters (5). The filter vent valve (2) permits air to be vented from the oil filters before the selector valve is moved.

DUPLEX LUBE FILTER SYSTEM
1. Selector (diverter) valve. 2. Filter vent valve. 3. Main filter. 4. Filter pressure gauges. 5. Auxiliary filter. 6. Adapting oil lines.

When the selector valve handle is parallel with the engine crankshaft, the flow of oil is to the main oil filters. When the handle is turned 90° away from the engine, the oil flow is to the auxiliary oil filters.

SCHEMATIC FLOW DIAGRAM OF DUPLEX LUBRICATION FILTER SYSTEM
1. Selector (diverter) valve. 2. Filter vent valve. 3. Main filter. 4. Filter pressure gauges. 5. Auxiliary filter. 7. Check valves. 8. Vent lines to engine crankcase from filters. 9. Pump for engine oil. 10. Oil cooler.

Prelubrication System - (16 Cylinder Engines Only)

The prelubrication system has an oil pump (1) that is turned by a motor (3). The motors used are: a 115/230 VAC, 24 VDC, 32 VDC, and an air motor. The motor and pump are mounted on the right side of the engine. The pump pulls oil from the oil pan base and then pushes the oil through a tube that connects to the engine oil line at tee (2). Check valve (4) is used to prevent the flow of engine oil backwards through the prelubrication pump to the oil pan base.

COMPONENT LOCATION
1. Oil pump. 2. Tee. 3. Electric motor. 4. Check valve.

When you start the engine, the prelubrication pump will give lubrication to the engine before the starting motors turn. When oil pressure at the oil lines to the turbochargers is 1 to 3 psi (7 to 20 kPa), a pressure switch will close and activate the starting motors. When the engine starts and the start switch or air valve is released the prelubrication pump stops.

Cooling System

FLOW OF COOLANT IN RADIATOR COOLING SYSTEM
1. Aftercooler. 2. Exhaust manifold. 3. Tubes. 4. Water manifold. 5. Regulator housing. 6. Radiator. 7. Bypass line. 8. Water pump. 9. Cylinder head. 10. Engine oil cooler. 11. Junction housing. 12. Bottom passage. 13. Flywheel housing. 14. Top passage.

Engine Jacket Water Cooling System

The two most used methods to remove heat from the engine jacket water are the radiator and the heat exchanger. The heat exchanger method must have an expansion tank to give room for the expansion of the coolant. The radiator has a top tank to give room for the expansion of the coolant.

A gear driven centrifugal-type water pump is used to move the coolant through the engine jacket water cooling system. The water pump is on the right side of the engine on the rear of the accessory drive housing.

The flow of coolant through the engine is as follows: Coolant from radiator (6) or expansion tank (16) is pulled through the inlet line by water pump (8). The water pump then pushes the coolant to engine oil cooler (10). From the oil cooler the coolant goes to top passage (14) in flywheel housing (13).

Coolant goes through the top passage in the flywheel housing to junction housing (11) on the left side. The coolant turns 180 degrees in the junction housing cover and goes into bottom passage (12) in the flywheel housing.

FLOW OF COOLANT IN HEAT EXCHANGER COOLING SYSTEM
1. Aftercooler. 2. Exhaust manifold. 3. Tubes. 4. Water manifold. 5. Regulator housing. 8. Water pump. 9. Cylinder head. 10. Engine oil cooler. 11. Junction housing. 12. Bottom s passage. 13. Flywheel housing. 14. Top passage. 15. Water cooled turbocharger shield. 16. Expansion tank. 17. Engine jacket water heat exchanger.

NOTE: On engines equipped with a jacket water aftercooler, part of the coolant goes to the aftercooler through a pipe from the top passage of the junction housing. The coolant goes through the front core of the aftercooler, and through a pipe to the rear core. From the rear aftercooler core the coolant goes through a pipe to the bottom passage of the junction housing. A plate with an orifice is installed between the junction housing and the junction housing cover, to cause the coolant to flow through the aftercooler.

In the bottom passage of the flywheel housing part of the coolant goes to the left side of the cylinder block. The remainder of the coolant goes across the flywheel housing into the right side of the cylinder block. The coolant then flows through the cylinder block, around the cylinder liners and into cylinder heads (9). Lines from the rear of the cylinder block let coolant go to water cooled turbocharger shield (15). Coolant goes from the shield through lines to either water cooled or water shielded exhaust manifolds (2).

Coolant from the cylinder heads goes through tubes (3) to the exhaust manifold shields or the water cooled exhaust manifolds and then to the front of the engine to water manifold (4).

Coolant goes from the water manifold to regulator housing (5). The regulators in the housing control the flow of coolant to the radiator or heat exchanger to control the temperature in the cooling system.

When the system has a radiator, there is a bypass line (7) from the inlet side of the regulator housing to the inlet pipe for the water pump. When the system has a heat exchanger and expansion tank, there is a bypass passage from the inlet side of the regulator housing to the expansion tank. In either system when the temperature of the coolant is not high enough to open the regulators, coolant will bypass the radiator or heat exchanger to permit quick warm-up of the engine.

Coolant Level Switch

Some systems with expansion tanks have a coolant level switch for the purpose of checking coolant level in the system. The coolant level is shown by the operating arm (2).

When the coolant level gets too low, the switch (1) can be used to sound an alarm, light a warning light or operate a device to stop the engine. A high coolant level alarm also can be connected to the switch.

COOLANT LEVEL SWITCH
1. Switch. 2. Operating arm.

Sea Water And Separate Circuit Aftercooler Water Systems

FLOW OF COOLANT IN SEA WATER COOLING SYSTEM
17. Engine jacket water heat exchanger. 18. Sea water pump. 19. Aftercooler inlet elbow. 20. Outlet elbow. 21. Marine gear oil cooler. 22. Flange. 23. Water outlet connection. 24. Flange.

Sea Water System

The sea water aftercooler system uses sea water (water that is not treated) to remove heat from the aftercooler cores and other cooling system components. A gear driven, centrifugal-type water pump is used to move the sea water through the system. The pump is on the left side of the engine on the accessory drive housing. Zinc rods are installed in the sea water system to help prevent corrosion of the system components. These rods must be replaced from time to time to keep the resistance of corrosion high. The plugs for the zinc rods have red paint for easy identification.

Sea water pump (18) pulls water through the inlet pipe and then pushes it through a pipe to aftercooler inlet elbow (19). A part of the water at the elbow goes to the front aftercooler core and through a pipe to the rear aftercooler core, and the remainder of the water goes through a pipe to outlet elbow (20). The restriction of the pipe to the outlet elbow will cause most of the water to go through the aftercooler. Water from the rear aftercooler core goes to the outlet elbow and mixes with the water from the inlet elbow.

NOTE: There is a plate with an orifice installed between the rear aftercooler core and the outlet elbow to help keep the aftercooler cores full of water.

FLOW OF COOLANT IN SEPARATE CIRCUIT COOLING SYSTEM
19. Aftercooler inlet elbow. 20. Outlet elbow. 21. Marine gear oil cooler. 22. Flange. 23. Water outlet connection. 24. Flange. 25. Fresh water pump. 26. Keel cooler. 27. Expansion tank.

Part of the water at the outlet elbow goes to marine gear oil cooler (21), and the remainder goes through flange (22) to water outlet connection (23). Water from the marine gear oil cooler goes to flange (24). There is a plate with an orifice installed between the aftercooler outlet elbow and flange (22) to make the water go through the marine gear oil cooler.

Water from the water outlet connection goes to the tube side of the engine jacket water heat exchanger (17). The water goes through the heat exchanger and then to the sea water outlet (overboard discharge).

Separate Circuit System

The separate circuit aftercooler system uses fresh water (water that is treated) to remove heat from the aftercooler cores and other cooling system components. A gear-driven centrifugal-type water pump is used to move the fresh water through the system. The pump is on the left side of the engine on the accessory drive housing.

Fresh water pump (25) pulls coolant through the inlet pipe and then pushes it through a pipe to the front aftercooler core. The coolant flows through the front aftercooler core and then through the rear aftercooler core to outlet elbow (20). Part of the coolant at the outlet elbow goes to marine gear oil cooler (21) and the remainder goes through flange (22) to water outlet connection (23). Coolant from the marine gear oil cooler goes to flange (24). There is a plate with an orifice installed between the aftercooler outlet elbow and flange (22) to make the coolant go through the marine gear oil cooler.

Coolant from the water outlet connection goes to keel cooler (26) or a fresh water heat exchanger which will remove the heat from the coolant. The coolant then returns to the water pump inlet pipe. An expansion tank (27) is installed in the inlet pipe to give room for expansion of the coolant.

Basic Block

Cylinder Block, Heads And Liners

The cylinder block is a 60° vee. There is a counterbore in the top of the block for each cylinder liner. The bottom of the counterbore is the support for each liner. Covers on the side of the cylinder block permit inspection or replacement of the connecting rod and main bearings without removal of the oil pan base.

The engine has one cylinder head for each two cylinders. The earlier block has studs to fasten the cylinder heads. The later block has bolts to fasten the cylinder heads.

Coolant in the engine flows around the liners to remove heat from them. Three o-ring seals at the bottom and a filler band at the top of each cylinder liner make 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 in the piston. The oil ring is spring loaded. Holes in the oil ring groove return oil to the crankcase.

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

A steel heat plug in the top of the piston prevents erosion (wearing away) of the top of the piston at the point of highest heat.

Piston cooling jets, located on the bottom of the valve lifter brackets, throw oil to cool and give lubrication to the piston components and cylinder walls.

The connecting rods and caps are cut at an angle which let the piston and connecting rod assembly be removed up through the cylinder liner. The connecting rod bearings are held in location with a tab that fits in a groove in the connecting rod and cap. The connecting rods must be installed with the part number toward the radius in the crankshaft journal.

Crankshaft

Combustion forces in the cylinder are changed into usable rotating power by the crankshaft. The crankshaft has a gear on each end. The gear at the front drives the gears in the accessory drive. The gear at the back drives the engine camshaft and the fuel injection pump camshaft. The crankshaft end play is controlled by thrust bearings on the rear main bearing cap. For an opposite rotation engine the crankshaft is turned end for end.

Timing Gears

The timing gears are in a compartment at the rear of the cylinder block. Their cover is the front face of the flywheel housing. The timing gears keep the rotation of the crankshaft, camshaft, balancers (8 cylinder engine), fuel pump and governor drive in the correct relation to each other. The timing gears are driven by a gear in front of the rear flange of the crankshaft.

TIMING GEARS (8 Cylinder Engine Illustrated)
1. Fuel pump and governor drive gear. 2. Camshaft cluster gear. 3. Balancer gear (8 cylinder engines only). 4. Crankshaft gear.

The crankshaft gear (4) turns the camshaft cluster gear (2). This gear turns the balancer gear (3) (8 cylinder engine) and gear (1) of the fuel pump and governor drive.

The small cluster gear of the camshaft is held to the camshaft with a key, plate and bolts.

Vibration Damper

The force from combustion in the cylinders will cause the crankshaft to twist. This is called torsional vibration. If the vibration is too great, the crankshaft will be damaged. The vibration damper limits torsional vibrations to an acceptable amount to prevent damage to the crankshaft.

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.

CROSS SECTION OF A TYPICAL VIBRATION DAMPER
1. Solid cast iron weight. 2. Space between weight and case. 3. Case.

The 8 cylinder engine has a short, rigid crankshaft and does not need a vibration damper except for some special applications. The 12 cylinder engine has one vibration damper. 16 Cylinder Engines have two vibration dampers.

Front Accessory Drive

The front accessory drive gives a location to operate accessories such as a sea water pump, fresh water pump, air compressor, hydraulic pump, and alternator. The engine oil pump, fuel transfer pump, and jacket water pump are also driven by the front accessory drive.

The direction of rotation of the accessory drive is the same for standard or opposite rotation engines.