Introduction

NOTE: For Specifications with illustrations, make reference to Specifications for 3408C & 3412C Marine Engines, SENR1147. If the Specifications in SENR1147 are not the same as in the Systems Operation, Testing & Adjusting, look at the printing date on the front cover of each book. Use the Specifications given in the book with the latest date.

Engine Design

3408C

Cylinder, Valve And Injection Pump Location

Number And Arrangement Of Cylinders ... 65 degree V-8

Valves Per Cylinder ... 4

Displacement ... 18.0 liters (1099 cu in)

Bore ... 137.2 mm (5.40 in)

Stroke ... 152.4 mm (6.00 in)

Compression Ratio ... 14.5:1

Type Of Combustion ... Direct Injection

Direction Of Crankshaft Rotation (as viewed from flywheel end) ... Counterclockwise

Direction Of Fuel Pump Camshaft Rotation (as viewed from pump drive end) ... Counterclockwise

Firing Order (Injection Sequence) ... 1-8-4-3-6-5-7-2

Valve Lash Setting

Inlet ... 0.38 mm (.015 in)

Exhaust ... 0.76 mm (.030 in)

NOTE: Front end of engine is opposite the flywheel end. Left side and right side of engine are as viewed from the flywheel end. No. 1 cylinder is the front cylinder on the left side. No. 2 cylinder is the front cylinder on the right side.

3412C

Cylinder, Valve And Injection Pump Location

Number And Arrangement Of Cylinders ... 65 degree V-12

Valves Per Cylinder ... 4

Displacement ... 27.0 liters (1649 cu in)

Bore ... 137.2 mm (5.40 in)

Stroke ... 152.4 mm (6.00 in)

Compression Ratio:

4P1980 (Piston & Rod Group) ... 14.5:1

4P7472 (Piston & Rod Group) ... 14.1:1

Type Of Combustion ... Direct Injection

Direction Of Crankshaft Rotation (as viewed from flywheel end) ... Counterclockwise

Direction Of Fuel Pump Camshaft Rotation (as viewed from pump drive end) ... Counterclockwise

Firing Order (Injection Sequence) ... 1-4-9-8-5-2-11-10-3-6-7-12

Valve Lash Setting

Inlet ... 0.38 mm (.015 in)

Exhaust ... 0.76 mm (.030 in)

NOTE: Front end of engine is opposite the flywheel end. Left side and right side of engine are as viewed from the flywheel end. No. 1 cylinder is the front cylinder on the left side. No. 2 cylinder is the front cylinder on the right side.

Fuel System

Fuel System Schematic
(1) Fuel tank. (2) Tank shutoff valve. (3) Fuel injection nozzle. (4) Fuel manifolds. (5) Fuel injection pump housing. (6) Bleed orifice. (7) Fuel inlet line (from secondary filters). (8) Fuel inlet line (from primary filter). (9) Check valve. (10) Fuel transfer pump. (11) Secondary fuel filter. (12) Primary fuel filter. (13) Fuel priming pump. (14) Fuel transfer pump relief valve.

There is one fuel injection pump and one fuel injection nozzle for each cylinder. The fuel injection pumps are located in the fuel injection pump housing. The fuel injection nozzles (3) are located in the injection adapter in the cylinder head.

When the engine is running, fuel is pulled from the fuel tank through the fuel supply line and primary fuel filter (12) by fuel transfer pump (10). The fuel is then pushed to secondary fuel filters (11), and into the fuel filter housing. A bleed orifice (6) in the fuel filter housing cover vents air in the system through a line back to fuel tank (1). Fuel from the fuel filter housing goes through fuel inlet line (7) to fuel manifolds (4) in fuel injection pump housing (5). The fuel manifolds supply fuel to each fuel injection pump.

Individual fuel injection lines carry fuel from the fuel injection pumps to each cylinder. One section of line connects between the fuel injection pump and an adapter on the valve cover base. Another section of line on the inside of the valve cover base connects between the adapter and the fuel injection nozzle (3).

The fuel filters and priming pump are located in a compartment at the front of the fuel tank. The fuel transfer pump is mounted on a drive adapter on the fuel injection pump housing, and is driven by a shaft connected to the fuel injection pump camshaft. Fuel transfer pump relief valve (14) is located in the cover of the pump.

Fuel priming pump (13) is used before the engine is started to put pressure in the fuel system and to vent air from the system. A check valve (9) located in the fuel transfer pump adapter housing will let fuel go around the fuel transfer pump when the priming pump is in use.

There is no bleed orifice or valve installed on the fuel injection pump housing to vent air from this part of the fuel system. Air trapped in the fuel injection lines can be vented by loosening all of the fuel injection line nuts where they connect to the adapters in the valve cover base. Move the governor lever to the low idle position. Crank the engine with the starting motor until fuel without air comes from the fuel line connections. Tighten the fuel line nuts. This procedure is necessary because the fuel priming pump will not give enough pressure to push fuel through the reverse flow check valves in the fuel injection pumps of a direct injection system.

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

Fuel Injection Pump

Cross Section Of The Fuel Injection Pump Housing
(1) Fuel manifold. (2) Inlet passage. (3) Check valve. (4) Pressure relief passage. (5) Pump plunger. (6) Spring. (7) Gear. (8) Fuel rack (left). (9) Lifter. (10) Link. (11) Lever. (12) Camshaft.

The rotation of the lobes on the camshaft (12) cause lifters (9) and pump plungers (5) to move up and down. The stroke of each pump plunger is always the same. The force of springs (6) hold lifters (9) against the cams of the camshaft.

The pump housing is a "V" shape (similar to the engine cylinder block). The 3408C has four pumps on each side and the 3412C has six pumps on each side.

When the pump plunger is down, fuel from fuel manifold (1) goes through inlet passage (2) and fills the chamber above pump plunger (5). As the plunger moves up it closes the inlet passage.

The pressure of the fuel in the chamber above the plunger increases until it is high enough to cause check valve (3) to open. Fuel under high pressure flows out of the check valve, through the fuel line to the injection valve, until the inlet passage opens into pressure relief passage (4) in the plunger. The pressure in the chamber decreases and check valve (3) closes.

The longer inlet passage (2) is closed, the larger the amount of fuel which will be forced through check valve (3). The period for which the inlet passage is closed is controlled by pressure relief passage (4). The design of the passage makes it possible to change the inlet passage closed time by rotation of the plunger. When the governor moves fuel racks (8), they move gears (7) that are fastened to pump plungers (5). This causes a rotation of the plungers.

The governor is connected to the left rack. The spring load on lever (11) removes the play between the racks and link (10). The fuel racks are connected by link (10). They move in opposite directions (when one rack moves in, the other rack moves out).

Fuel Injection Nozzles

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

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

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

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

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

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

Hydra-Mechanical Governor

The throttle lever, or governor control, is connected to the control lever on the engine governor. The governor then controls the amount of fuel needed to keep the desired engine rpm at the throttle lever setting.

Hydra-Mechanical Governor
(1) Collar. (2) Bolt. (3) Lever assembly. (4) Upper spring seat. (5) Governor weights. (6) Governor spring. (7) Lower spring seat. (8) Thrust bearing. (9) Valve. (10) Upper oil passage (in piston). (11) Piston. (12) Lower oil passage (in piston). (13) Sleeve. (14) Oil passage (in cylinder). (15) Drive assembly. (16) Cylinder. (17) Pin. (18) Lever.

The governor has governor weights (5) driven by the engine through the drive assembly (15). The governor has a governor spring (6), valve (9) and piston (11). The valve and piston are connected to one fuel rack through pin (17) and lever (18). The pressure oil for the governor comes from the governor oil pump, on top of the injection pump housing. The oil used is from the engine lubrication system. Pressure oil goes through oil passage (14) and around sleeve (13). The throttle lever, or governor control, controls only the compression of governor spring (6). Compression of the spring always pushes down to give more fuel to the engine. The centrifugal force of governor weights (5) always pulls to get a reduction of fuel to the engine. When these two forces are in balance, the engine runs at the desired rpm (governed rpm).

The governor valve (9) is shown in the position when the force of the governor weights and the force of the governor spring are in balance.

When the engine load increases, the engine rpm decreases and the rotation of governor weights (5) will get slower. (The governor weights will move toward each other). Governor spring (6) moves valve (9) down. This lets the oil flow from the lower oil passage (12) around the valve (9) and through the upper oil passage (10) to fill the chamber behind piston (11). This pressure oil pushes the piston (11) and pin (17) down to give more fuel to the engine. (The upper end of the valve stops the oil flow through the top of the piston, around the valve). Engine rpm goes up until the rotation of the governor weights is fast enough to be in balance with the force of the governor spring.

When there is a reduction in engine load, there will be an increase in engine rpm and the rotation of governor weights (5) will get faster. This will move valve (9) up. This stops oil flow from the lower oil passage (12), and oil pressure above piston (11) goes out through the top, around valve (9). Now, the pressure between the sleeve (13) and piston (11) pushes the piston and pin (17) up. This causes a reduction in the amount of fuel to the engine. Engine rpm goes down until the centrifugal force (rotation) of the governor weights is in balance with the force of the governor spring. When these two forces are in balance, the engine will run at the desired rpm (governed rpm).

When engine rpm is at Low Idle, a spring-loaded plunger in lever assembly (3) comes in contact with a shoulder on the adjustment screw for low idle. To stop the engine, push throttle lever to vertical position. This will let the spring-loaded plunger move over the shoulder on the low idle adjustment screw and move the fuel rack to the fuel closed position. With no fuel to the engine cylinders, the engine will stop.

The governor oil pump supplies oil to the valve (9) to increase governor power and response. Oil from the governor oil pump gives lubrication to the governor weight support (with gear), thrust bearing (8), and drive gear bearing. The other parts of the governor get lubrication from "splash-lubrication" (oil thrown by other parts). Oil from the governor runs down into the housing for the fuel injection pumps.

Fuel Ratio Control

Fuel Ratio Control (Engine Stopped)
(1) Inlet air chamber. (2) Valve. (3) Diaphragm assembly. (4) Oil drains. (5) Pressure oil chamber. (6) Large oil passages. (7) Oil inlet. (8) Small oil passages. (9) Oil outlet. (10) Fuel rack linkage. (11) Valve.

With the engine stopped, valve (11) is in the fully extended position. The movement of fuel rack linkage (10) is not limited by valve (11).

Fuel Ratio Control (Ready For Operation)
(1) Inlet air chamber. (2) Valve. (5) Pressure oil chamber. (6) Large oil passages. (8) Small oil passages. (11) Valve.

When the engine is started, oil flows through oil inlet (7) into pressure oil chamber (5). From pressure oil chamber (5) the oil flows through large oil passages (6), inside valve (11), and out small oil passages (8) to oil outlet (9).

A hose assembly connects inlet air chamber (1) to the inlet air system. As the inlet air pressure increases, it causes diaphragm assembly (3) to move down. Valve (2), that is part of the diaphragm assembly, closes large and small oil passages (6 and 8). When these passages are closed, oil pressure increases in pressure oil chamber (5). This increase in oil pressure moves valve (11) up. The control is now ready for operation.

When the governor control is moved to increase fuel to the engine, valve (11) limits the movement of fuel rack linkage (10) in the "Fuel On" direction. The oil in pressure oil chamber (5) acts as a restriction to the movement of valve (11) until inlet air pressure increases.

Fuel Ratio Control (Increase In Inlet Air Pressure)
(2) Valve. (4) Oil drains. (5) Pressure oil chamber. (10) Fuel rack linkage. (11) Valve.

As the inlet air pressure increases, valve (2) moves down and lets oil from pressure oil chamber (5) drain through large oil passages (6) and out through oil drains (4). This lets valve (11) move down so fuel rack linkage (10) can move gradually to increase fuel to the engine. The control is designed not to let the fuel increase 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.

The control movements take a very short time. No change in engine acceleration (rate at which speed increases) can be felt.

Automatic Timing Advance Unit

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

The automatic timing advance unit is installed on the front of the camshaft (6) for the fuel injection pump and is gear driven through the timing gears. The drive gear (5) for the fuel injection pump is connected to camshaft (6) through a system of weights (2), springs (3), slides (4) and flange (1). Each one of the two slides (4) is held on drive gear (5) by a pin. The two weights (2) can move in guides inside flange (1) and over slides (4), but the notch for the slide in each weight is at an angle with the guides for the weight in the flange. As centrifugal force (rotation) moves the weights away from the center, against springs (3), the guides in the flange and the slides on the gear make the flange turn a small amount in relation to the gear. Since the flange is connected to the camshaft for the fuel injection pump, the fuel injection timing is also changed. No adjustment can be made in the timing advance unit.

Air Inlet And Exhaust System

The air inlet and exhaust system components are: air cleaner, turbocharger, inlet manifold (passages inside the cylinder block), cylinder head, valves and valve system components, and exhaust manifold.

Air Inlet And Exhaust System
(1) Exhaust manifold. (2) Pipe to inlet manifold. (3) Engine cylinders. (4) Air inlet. (5) Compressor wheel. (6) Turbine wheel. (7) Exhaust outlet.

Air Flow Schematic
(1) Exhaust manifold. (2) Pipe to inlet manifold. (4) Air inlet. (7) Exhaust outlet. (8) Turbocharger.

Clean inlet air from the air cleaner is pulled through air inlet (4) of the turbocharger by the turning of turbocharger compressor wheel (5). The compressor wheel causes a compression of the air. The air then goes through pipe to inlet manifold (2) of the engine.

When the inlet valves open, the air goes into engine cylinders (3) and is mixed with the fuel for combustion. When the exhaust valves open, the exhaust gases go out of the engine cylinders and into exhaust manifold (1). From exhaust manifold, the exhaust gases go through the blades of turbine wheel (6). This causes the turbine wheel and compressor wheel to turn. The exhaust gases then go out exhaust outlet (7) of the turbocharger.

Aftercooler

The aftercooler cools the air coming out of the turbocharger before it goes into the inlet manifold. The aftercooler is located toward the rear of the engine between the cylinder heads. Coolant from the water pump flows through a pipe into the aftercooler. It flows through the core assembly, then out of the aftercooler through a different pipe into the rear of the cylinder block. Inlet air from the compressor side of the turbocharger flows into the aftercooler through pipes. The air passes through the core assembly. This lowers the temperature of the air to approximately 93°C (200°F). The cooler air goes out the bottom of the aftercooler into the inlet manifold. The purpose of this is to make the air going into the combustion chambers more dense. The more dense the air is, the more fuel the engine can burn efficiently. This gives the engine more power.

Turbocharger

The turbocharger is installed at the top, rear of the engine on a cross pipe for the two exhaust manifolds. All the exhaust gases from the engine go through the turbocharger.

Typical Example
(1) Turbocharger. (2) Cross pipes. (3) To exhaust manifold.

Turbocharger
(4) Air inlet. (5) Compressor wheel. (6) Turbine wheel. (7) Exhaust outlet. (8) Compressor housing. (9) Oil inlet port. (10) Thrust collar. (11) Thrust bearing. (12) Turbine housing. (13) Spacer. (14) Air outlet. (15) Oil outlet port. (16) Bearing. (17) Coolant passages. (18) Bearing. (19) Exhaust inlet.

The exhaust gases go through the blades of turbine wheel (6). This causes the turbine wheel and compressor wheel (5) to turn, which causes a compression of the inlet air.

When the load on the engine is increased, more fuel is put into the engine. This makes more exhaust gases and will cause the turbine and compressor wheels of the turbocharger to turn faster. As the turbocharger turns faster, it gives more inlet air and makes it possible for the engine to burn more fuel and will give the engine more power.

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.

Bearings (16 and 18) for the turbocharger use engine oil under pressure for lubrication. The oil comes in through the oil inlet port (9) and goes through passages in the center section for lubrication of the bearings. Oil from the turbocharger goes out through the oil outlet port (15) in the bottom of the center section and goes back to the engine lubrication system.

This type turbocharger has coolant passages (17) around the bearings to cool the oil in these areas. Engine coolant is taken from the top, rear of the engine and sent into the rear of the turbocharger (center section). The coolant flows through the passages around the bearings, and out the front of the turbocharger (center section) back to the radiator top tank.

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.

Valve System Components

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

The crankshaft gear drives the camshaft gear. The camshaft gear must be timed to the crankshaft gear to get the correct relation between piston and valve movement.

The camshaft has two cams for each cylinder. One cam controls the exhaust valves, the other controls the inlet valves.

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

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

As the camshaft turns, the lobes of camshaft (9) cause lifters (8) to go up and down. This movement makes push rods (3) move rocker arms (2 and 10). Movement of the rocker arms makes the bridges move up and down on dowels mounted in the cylinder head. The bridges let one rocker arm open and close two valves (inlet or exhaust). There are two inlet and two exhaust valves for each cylinder.

Rotocoils (4) cause the valves to turn while the engine is running. The rotation of the valves keeps the deposit of carbon on the valves to a minimum and gives the valves longer service life.

Valve springs (5) cause the valves to close when the lifters move down.

Lubrication System

Oil Flow Through The Engine Oil Cooler And Engine Oil Filters

Schematic Of Oil Flow
(1) To oil manifold. (2) Filter bypass valve. (3) Engine oil cooler. (4) Cooler bypass valve. (5) Engine oil pump. (6) Oil pan. (7) Engine oil filters.

With the engine warm (normal operation), oil is pulled from oil pan (6) through a suction bell assembly and pipe to engine oil pump (5). The engine oil pump sends oil to a passage in the cylinder block. The oil then goes through engine oil cooler bypass valve (4) into engine oil cooler (3). The oil goes out of the engine oil cooler through engine oil filters (7). The clean oil then goes through oil filter bypass valve (2), then into the oil manifold on the right side of the cylinder block.

When the engine is cold (starting condition), bypass valves (2 and 4) open because cold oil with high viscosity causes a restriction to the oil flow through engine oil cooler (3) and engine oil filters (7). With the bypass valves open, oil flows directly through passages in the valve body to the oil manifold.

When the oil gets warm, the pressure difference at the bypass valves decreases and the bypass valves close. This gives normal oil flow through engine oil cooler (3) and engine oil filters (7).

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

There is also a bypass valve in engine oil pump (5). This bypass valve controls the pressure of the oil from the engine oil pump. The engine oil pump can put more oil into the system than is needed. When there is more oil than needed, the oil pressure goes up and the bypass valve will open. This lets the oil that is not needed to go back to the inlet oil passage of the engine oil pump.

Oil Flow In The Engine

Schematic Of Oil Flow In The 3408C Engine
(1) Passage is plugged. (2) Passage (to rear idler gear). (3) Passage (to rocker arm shaft). (4) To turbocharger. (5) Passage (to fuel injection pump housing, governor and fuel ratio control). (6) Rocker arm shaft. (7) Passages (to rocker arm shaft and valve lifters). (8) Passages (to valve lifters). (9) Camshaft bearing bores. (10) Piston cooling jets. (11) To SCAC water pump. (12) Oil manifold (left side). (13) To timing gear housing. (14) Passage (to front idler gear). (15) Oil supply line (to manifold in cylinder block). (16) Oil manifold (right side). (17) Main bearing bores.

The oil manifolds are cast into the sides of the cylinder block. Oil goes into oil manifold (16) from the bypass valve body. From oil manifold (16) oil is sent to oil manifold (12) through drilled passages in the cylinder block that connect main bearing bores (17) and camshaft bearing bores (9). Oil goes through holes in the bearings and gives them lubrication. Oil from the main bearings goes through holes drilled in the crankshaft to give lubrication to the connecting rod bearings. A small amount of oil from the oil manifolds goes through piston cooling jets (10) to make the pistons cooler.

Oil goes through grooves in the outside of the front and rear camshaft bearings to passages (7 and 8). The oil in these passages gives lubrication to the valve lifters and rocker arm shafts. Holes in the rocker arm shafts lets the oil give lubrication to the valve system components in the cylinder head.

The fuel injection pump and governor gets oil from passage (5) in the cylinder block. There is a small gear pump between the injection pump housing and the governor. This pump sends oil under pressure for the hydraulic operation of the hydra-mechanical governor. The automatic timing advance unit gets oil from the injection pump housing, through the camshaft for the fuel injection pumps.

The idler gear bore gets oil from passage (14) in the cylinder block, oil then goes through the shaft for the bearings of the idler gear installed on the front of the cylinder block.

The bearing for the balancer gear at the rear of the engine (3408C only) gets oil through a passage in the balancer gear shaft that is connected to passage (2).

Turbocharger Lubrication (Typical Example)
(18) Oil supply line (to turbocharger). (19) Oil drain line (from turbocharger).

Oil supply line (18) gives oil to the turbocharger impeller shaft bearings. The oil goes out of the turbocharger through oil drain line (19) to the flywheel housing.

Oil that gives pressure lubrication to gear shafts and bearings then flows free to give lubrication to the gear teeth. After the oil for lubrication has done its work it flows back to the oil pan.

Schematic Of Oil Flow In The 3412C Engine
(1) Passage is plugged. (3) Passage (to rocker arm shaft). (4) To turbocharger. (5) Passage (to fuel injection pump housing, governor and fuel ratio control). (6) Rocker arm shaft. (7) Passages (to rocker arm shaft and valve lifters). (8) Passages (to valve lifters). (9) Camshaft bearing bores. (10) Piston cooling jets. (11) To SCAC water pump. (12) Oil manifold (left side). (13) To timing gear housing. (14) Passage (to front idler gear). (15) Oil supply line (to manifold in cylinder block). (16) Oil manifold (right side). (17) Main bearing bores.

Cooling System

Jacket Water Aftercooler

Cooling System Schematic
(1) Aftercooler elbow. (2) Aftercooler. (3) Front housing. (4) Temperature regulator housing. (5) Bypass lines. (6) Water cooled exhaust manifold. (7) Jacket water coolant source. (8) Water cooled turbocharger. (9) Engine oil cooler. (10) Jacket water pump.

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

In normal operation (engine warm), jacket water pump (10) receives coolant through the inlet connection. The jacket water pump (10) forces water out in two directions. Part of it flows to the aftercooler (2). The coolant goes through the aftercooler core and enters into the cylinder block at the top rear through aftercooler elbow (1). Part of the coolant flows through the engine oil cooler (9) and into the side of the cylinder block.

Coolant moves through the cylinder block to the cylinder heads. The coolant then goes to the temperature regulator housing (4). The temperature regulators are open and most of the coolant goes through the outlets and back to the coolant source.

NOTE: The water temperature regulator is an important part of the cooling system. It divides coolant flow between jacket water coolant source (7) and bypass lines (5) 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 back to the coolant source is too much, and the engine will not get to normal operating temperatures.

When the engine is cold, the water temperature regulator is closed, and the coolant is stopped from going back to the coolant source. The coolant goes from the temperature regulator housing (4) back to the jacket water pump (10) through bypass lines (5).

These engines are equipped with a water cooled exhaust manifold (6) and a water cooled turbocharger (8). The coolant for the exhaust manifold comes from the back of the cylinder head through the exhaust manifold and out into the water temperature regulator housing. The coolant for the turbocharger comes from the engine oil cooler (9) through the tube to the turbocharger. The coolant goes out of the turbocharger and into the water cooled exhaust manifold.

Separate Circuit Aftercooler

Cooling System Schematic
(1) Separate circuit coolant source. (2) Aftercooler. (3) Water cooled exhaust manifold. (4) Front housing. (5) Temperature regulator housing. (6) Bypass lines. (7) Separate circuit water pump. (8) Water cooled turbocharger. (9) Engine oil cooler. (10) Water pump. (11) Jacket water coolant source.

Jacket Water System

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

In normal operation (engine warm), water pump (10) receives coolant through the inlet connection and sends the coolant to engine oil cooler (9) and the oil cooler bypass. The engine oil cooler outlet sends the coolant from the cooler and bypass to the engine cylinder block. The coolant to the cylinder block circulates through the block up through the cylinder heads, on to the water temperature regulator housing (5). Part of the coolant in water temperature regulator housing (5) flows into water pump (10), and part of the coolant passes through open water temperature regulators through the outlet connections to be cooled. The water pump (10) will pump the cooled coolant through the engine to keep the cycle going.

These engines are equipped with water cooled exhaust manifold (3) and water cooled turbocharger (8). The coolant for the exhaust manifold comes from the back of the cylinder head through the exhaust manifold and out into the water temperature regulator housing (5). The coolant for water cooled turbocharger (8) comes from the engine oil cooler through the tube to the water cooled turbocharger. The coolant goes out of the water cooled turbocharger and into water cooled exhaust manifold (3).

NOTE: The water temperature regulator is an important part of the cooling system. It divides coolant flow between the coolant source and bypass lines (6) 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 or heat exchanger is too much, and the engine will not get to normal operation temperatures.

When the engine is cold, the water temperature regulators are closed. The coolant in the water temperature regulator housing (5) flows through bypass lines (6) to water pump (10). The coolant continues to flow through system as described above except the coolant does not flow out to be cooled.

Separate Circuit Aftercooler (SCAC) System

The aftercooler (2) is cooled by a separate circuit. The separate circuit is used to maintain a specific and constant water temperature. Water is pumped from separate circuit coolant source (1) by separate circuit water pump (7) through the aftercooler and back to the water supply.

Keel Cooled System

Example Of Keel Cooled System
(1) Water cooled turbocharger. (2) Aftercooler. (3) Connection [inlet for engine water return (either side)]. (4) Vent lines. (5) Water temperature regulator (both sides). (6) Connection (for auxiliary tank). (7) Connection (outlet for engine water). (8) Engine water pump. (9) Keel cooler. (10) Duplex filter. (11) Bypass filter. (12) Oil cooler bypass or marine gear cooler. (13) Engine oil cooler. (14) Water cooled exhaust manifold.

With this cooling system an expansion tank is used, but the coolant flow in the engine is the same as the radiator cooled system. The coolant flows through the engine and back to the expansion tank in a constant cycle. When the temperature becomes high enough to open the regulators, the coolant flow is directed out through connection (7) to the keel cooling system, then back to the expansion tank through connection (3). The engine coolant is cooled as it flows through the keel cooler (9) by the sea water flowing past the cooling pipes on the keel.

Heat Exchanger Cooled System

Example Of Heat Exchanger Cooled System
(1) Water cooled turbocharger. (2) Aftercooler. (3) Connection [inlet for engine water return (either side)]. (4) Vent lines. (5) Water temperature regulator (both sides). (6) Auxiliary water pump. (7) Connection (outlet for engine water). (8) Engine water pump. (9) Duplex filter. (10) Heat exchanger. (11) Oil cooler bypass or marine gear cooler. (12) Engine oil cooler. (13) Water cooled exhaust manifold.

When the engine is cooled by the heat exchanger system, auxiliary water pump (6) is used to constantly pump filtered water from another source (either sea water or storage water) through the heat exchanger. When the engine reaches a temperature high enough to open the regulators, the coolant flow is directed around heat exchanger core (10) and then back to the expansion tank. The cooled coolant in the expansion tank is then pickled up by engine water pump (8) and directed back through the engine.

Coolant Conditioner (An Attachment)

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

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

The element has a specific amount of inhibitor for acceptable cooling system protection. As coolant flows through the element, the corrosion inhibitor, which is dry material, dissolves (goes into solution) and mixes to the correct concentration. Two basic types of elements are used for the cooling system, and they are called the "Precharge" and the "Maintenance" elements. Each type of element has a specific use and must be used correctly to get the necessary concentration for cooling system protection. The elements also contain a filter and should be left in the system so coolant flows through it after the conditioner material is dissolved.

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

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

Basic Block

Cylinder Block, Liners And Heads

The cylinders in the left side of the block make an angle of 65 degrees with the cylinders in the right side of the block. The main bearing caps are fastened to the block with two bolts per cap.

The cylinder liners can be removed for replacement. The top surface of the block is the seat for the cylinder liner flange. Engine coolant flows around the liners to keep them cool. Three O-ring seals around the bottom of the liner make a seal between the liner and the block.

The engine has a single, cast head on each side. Four vertical valves (two inlet and two exhaust), controlled by a pushrod valve system, are used per each cylinder. The opening for the fuel nozzles is located between the four valves. Series ports (passages) are used for both inlet and exhaust valves.

A steel spacer plate is used between the cylinder head and block. A thin gasket is used between the (plate and liners) and the block to seal water and oil. A thick gasket of metal and asbestos is used between the plate and the head to seal combustion gases, water and oil.

The size of the pushrod openings through the head permits the removal of the valve lifters with the head installed.

Valve guides without shoulders are pressed into the cylinder head.

Pistons, Rings And Connecting Rods

The aluminum pistons have three rings; two compression rings and one oil ring. All rings are located above the piston pin bore. The two compression rings are of the Keystone type, which have a tapered shape. The seat for the rings is an iron band that is cast into the piston. The action of the rings in the piston groove, which is also tapered, helps prevent seizure of the rings caused by too much carbon deposits. The oil ring is a standard (conventional) type. Oil returns to the crankcase through openings in the oil ring groove.

The piston pin is held in place by two snap rings that fit in grooves in the pin bore of the piston. The connecting rod has a taper on the pin bore end. This gives the rod and piston more strength in the areas with the most load.

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

Crankshaft

The crankshaft changes the combustion forces in the cylinder into usable rotating torque which powers the machine. Vibration, caused by combustion impacts along the crankshaft, is kept small by a vibration damper on the front of the crankshaft.

There is a gear at the front of the crankshaft to drive the timing gears and the engine oil pump. Seals and wear sleeves are used at both ends of the crankshaft for easy replacement and a reduction of maintenance cost. Pressure oil is supplied to all bearing surfaces through drilled holes in the crankshaft. The crankshaft is supported by five main bearings on the 3408C and seven main bearings on the 3412C. A thrust plate at either side of the center main bearing controls the end play of the crankshaft.

Camshaft

The engine has a single camshaft that is driven at the front end. It is supported by five bearings on the 3408C and seven bearings on the 3412C. As the camshaft turns, each cam (lobe) (through the action of the valve system components) moves either two exhaust valves or two inlet valves for each cylinder. The camshaft gear must be timed to the crankshaft gear. The relation of the cam (lobes) to the camshaft gear cause the valves in each cylinder to open and close at the correct time.

Vibration Damper

Cross Section Of A Vibration Damper
(1) Flywheel ring. (2) Rubber ring. (3) Inner hub.

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

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

Electrical System

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

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

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

The electrical systems include a Diagnostic Connector which is used when testing the charging and starting circuits.

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

Charging System Components

Alternator (4N3986, 4N3987, 5N5692)

Alternator (4N3986, 4N3987)
(1) Rectifier. (2) Rotor assembly. (3) Stator winding. (4) Coil and support assembly. (5) Ball bearing. (6) Regulator. (7) Roller bearing. (8) Fan.

Alternator (5N5692)
(1) Regulator. (2) Roller bearing. (3) Stator winding. (4) Ball bearing. (5) Rectifier bridge. (6) Field winding. (7) Rotor assembly. (8) Fan.

The alternator is driven by belts from the crankshaft pulley. This alternator is a three phase, self-rectifying charging unit, and the regulator is part of the alternator. The alternators (4N3986, 4N3987) have a 60 amp output. The alternator (5N5692) has a 45 amp output.

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

Alternator (6T1395)

Alternator
(1) Rotor assembly. (2) Stator assembly. (3) Brush assembly. (4) Regulator. (5) Bearings. (6) Capacitor. (7) Slip rings.

The alternator is driven by belts from the crankshaft pulley. It is a 24 volt, 35 ampere unit with a regulator which is a solid state (transistor, stationary parts) electronic switch installed on the side opposite the pulley. The alternator is made up of a head assembly on the drive end, rotor assembly, stator assembly, rectifier and heat removal assemblies, brush and holder assembly, head assembly on the ring end and regulator.

The rotor assembly has the field windings (wires around an iron core) which make magnetic lines of force when direct current (DC) flows through them. As the rotor turns, the magnetic lines of force are broken by the stator. This makes an alternating current (AC) in the stator.

The rectifier has diodes which change the alternating current (AC) from the stator to direct current (DC). Most of the direct current (DC) goes to charge the battery and make a supply of direct current (DC) for the low amperage circuit. The remainder of the direct current (DC) is sent to the field windings through the brushes.

Alternator Regulator (7T5665, 3T6354, 6T9445)

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.

Starting System Components

Solenoid

A solenoid is an electromagnetic switch that does two basic operations:

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

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

Typical Solenoid Schematic

The solenoid has windings (one or two sets) 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 starting motor begins to turn the flywheel of the engine.

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

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

Starting Motor

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

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

The starting motor has a solenoid. When the start switch is turned to the START position, the solenoid will be activated electrically. The solenoid core will now move to push the starting pinion, by a mechanical linkage, to engage with the ring gear on the flywheel of the engine. The starting pinion will engage with the ring gear before the electric contacts in the solenoid close the circuit between the battery and the starting motor. When the circuit between the battery and the starting motor is complete, the pinion will turn the engine flywheel. A clutch gives protection for the starting motor so that the engine, when it starts to run, can not turn the starting motor too fast. When the start switch is released, the starting pinion will move away from the flywheel ring gear.

Magnetic Switch

A magnetic switch (relay) is used sometimes for the starter solenoid circuit. Its operation electrically is the same as the solenoid. Its function is to reduce the current load on the start switch and control current to the starter solenoid.

Other Components

Circuit Breaker

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

A heat activated metal disc with a contact point makes complete the electric current through the circuit breaker. If the current in the electrical system gets too high, it causes the metal disc to get hot. This heat causes a distortion of the metal disc which opens the contacts and breaks the circuit.

Shutoff Solenoid

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

Air Starting System

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

Typical Air Starting System
(1) Air start control valve. (2) Air starting motor. (3) Relay valve. (4) Oiler.

The air starting motor (2) can be mounted on either side of the engine. Air is normally contained in a storage tank and the volume of the tank will determine the length of time the engine flywheel can be turned. The storage tank must hold this volume of air at 1720 kPa (250 psi) when filled.

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

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

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

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

Air Starting Motor
(5) Air inlet. (6) Vanes. (7) Rotor. (8) Pinion. (9) Gears. (10) Piston. (11) Piston spring.

The air from the supply goes to relay valve (3). The air start control valve (1) is connected to the line before the relay valve. The flow of air is stopped by the relay valve until air start control valve (1) is activated. The air from air start control valve goes to piston (10) behind pinion (8) for the starter. The air pressure on piston (10) puts piston spring (11) in compression and puts pinion (8) in engagement with the flywheel gear. When the pinion is in engagement, air can go out through another line to relay valve. The air activates relay valve which opens the supply line to the air starting motor.

The flow of air goes through the oiler (lubricator) (4) where it picks up lubrication for the air starting motor.

The air with lubrication goes into the air motor through air inlet (5). The pressure of the air pushes against vanes (6) in rotor (7), and then exhausts through the outlet. This turns the rotor which is connected by gears (9) and a drive shaft to pinion (8) which turns the engine flywheel.

When the engine starts running, the flywheel will start to turn faster than pinion (8). The pinion (8) retracts under this condition. This prevents damage to the motor, pinion (8) or flywheel gear.

When air start control valve (1) is released, the air pressure and flow to piston (10) behind pinion (8) is stopped, piston spring (11) retracts pinion (8). Relay valve (3) stops the flow of air to the air starting motor.

Power Take-Off Clutch (Front)

Power Take-Off Clutch (Typical Illustration)
(1) Ring. (2) Driven discs. (3) Link assemblies. (4) Lever. (5) Key. (6) Collar assembly. (7) Nut. (8) Yoke assembly. (9) Hub. (10) Plates. (11) Output shaft.

Power take-off clutches (PTOs) are used to send power from the engine to accessory components. For example, a PTO can be used to drive an air compressor or a water pump.

The PTO is driven by a ring (1) that has spline teeth around the inside diameter. The ring can be connected to the front or rear of the engine crankshaft by an adapter.

NOTE: On some PTOs located at the rear of the engine, ring (1) is a part of the flywheel.

The spline teeth on the ring engage with the spline teeth on the outside diameter of driven discs (2). When lever (4) is moved to the ENGAGED position, yoke assembly (8) moves collar assembly (6) in the direction of the engine. The collar assembly is connected to four link assemblies (3). The action of the link assemblies will hold the faces of driven discs (2), plates (10) and hub (9) tight together.

Friction between these faces permits the flow of torque from ring (1), through driven discs (2), to plates (10) and hub (9), Spline teeth on the inside diameter of the plates drive the hub. The hub is held in position on the output shaft (11) by a taper, nut (7) and key (5).

NOTE: A PTO can have from one to three driven discs (2) with a respective number of plates.

When lever (4) is moved to the NOT ENGAGED position, yoke assembly (8) moves collar assembly (6) to the left. The movement of the collar assembly will release link assemblies (3). With the link assemblies released there will not be enough friction between the faces of the clutch assembly to permit a flow of torque.