3408 & 3408B DIESEL TRUCK ENGINE Caterpillar


Systems Operation

Usage:



Engine Design


Cylinder, Valve And Injection Pump Location

Bore ... 5.40 in.(137.2 mm)

Stroke ... 6.00 in.(152.4 mm)

Number and Arrangement of Cylinders ... V-8

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

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

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

NOTE: Front end of engine is opposite to flywheel end.

Left side and right side of engine are as seen from 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 inlet line for the injection pump housing. (2) Damper. (3) Adapter with orifice. (4) Injection pump housing. (5) Fuel return line. (6) Fuel tank. (7) Fuel supply line. (8) Primary fuel filter. (9) Fuel transfer pump. (10) Fuel priming pump. (11) Main fuel filter.

This engine has a pressure type fuel system. There is one injection pump and injection nozzle for each cylinder. The injection pumps are in the pump housing (4) on top front of the engine. The injection nozzles are in the precombustion chambers or adapters (for engines with direct injection) under the valve covers.

The transfer pump (9) pulls fuel from the fuel tanks (6) through the primary filter (8) and sends it through the priming pump (10), main filter (11) and to the manifold of the injection pump housing. The fuel in the manifold of the injection pump housing goes to the injection pumps. The injection pumps are in time with the engine and send fuel to the injection nozzles under high pressure.

Some of the fuel in the manifold is constantly sent back through the return line (5) to the fuel tank to remove air from the system. On the outlet elbow of the injection pump there is a damper (2) to reduce shock loads, and a restriction orifice (3) to keep fuel pressure high and to control the amount of fuel that goes back to the fuel tank.


Location Of Fuel System Components
(1) Fuel inlet line for the injection pump housing. (2) Damper. (4) Injection pump housing. (9) Fuel transfer pump. (10) Fuel priming pump. (11) Main fuel filter. (12) Nut for a fuel injection line at the injection pump. (13) Fuel manifold across the injection pump housing. (14) Adapter through the valve cover base.

The fuel priming pump (10) is used to fill the system with fuel and to remove air from the fuel filter, fuel lines and components.

The transfer pump has a bypass valve and a check valve. The bypass valve (lower side) controls the maximum pressure of the fuel. The extra fuel goes to the inlet of the pump. The check valve allows the fuel from the tank to go around the transfer pump gears when the priming pump is used.

Fuel Injection Pump

The rotation of the cams 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), with four 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 nozzle, 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 plungers (5). This causes a rotation of the plungers.


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 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

Fuel, under high pressure from the injection pumps, is sent through the injection nozzles. The injection nozzles change the fuel to the correct fuel characteristic (spray pattern) for good combustion in the cylinders.

The fuel injection nozzles are installed in the precombustion chambers in engines equipped with precombustion chambers. An adapter takes the place of the precombustion chamber in engines equipped with direct injection. The precombustion chambers or adapters are installed in the cylinder heads.

7000 Series Fuel Injection Nozzles (On Later Engines)

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 earlier and later governors illustrated operate the same. The earlier governors have two levers (18) and the later governors have a one piece lever (18). The shutoff solenoid and fuel ratio control have been moved from the injection pump housing to the governor housing on the later governors.

The accelerator pedal, or governor control, is connected to the control lever on the engine governor. The governor controls the amount of fuel needed to keep the desired engine speed (rpm).


Hydra-Mechanical Governor (Earlier)
(1) Collar. (2) Bolt. (3) Lever assembly. (4) Upper spring seat. (5) 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) Levers.

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 passage (14) and around sleeve (13). The accelerator, 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 passage (12) around the valve (9) and through the upper 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.


Hydra-Mechanical Governor
(1) Collar. (2) Bolt. (3) Lever assembly. (4) Upper spring seat. (5) 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.

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 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).

To stop an engine equipped with a shutoff solenoid, turn the switch to the "OFF" position. This will cause the shutoff solenoid to move a lever that moves 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).

When the engine is started, oil flows through oil inlet (7) into pressure oil chamber (5). From 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 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 chamber (5) acts as a restriction to the movement of valve (11) until inlet air pressure increases.


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.

As the inlet air pressure increases, valve (2) moves down and lets oil from 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.


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

Automatic Timing Advance Unit

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 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.


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

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) Turbocharger compressor wheel. (6) Turbocharger turbine wheel. (7) Exhaust outlet.


Air Inlet And Exhaust System
(1) Exhaust manifold. (2) Aftercooler. (4) Air inlet. (7) Exhaust outlet. (8) Turbocharger. (9) Cylinder head.

Clean inlet air from the air cleaner is pulled through air inlet (4) of the turbocharger by the turning of 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 intake 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.


Air Flow Schematic (Engines With Aftercooler)
(1) Exhaust manifold. (2) Aftercooler. (4) Air inlet. (7) Exhaust outlet. (8) Turbocharger.


Air Flow Schematic (Engines Without Aftercooler)
(1) Exhaust manifold. (2) Pipe to inlet manifold. (4) Air inlet. (7) Exhaust outlet. (8) Turbocharger.

Aftercooler


Air Inlet System
(1) Aftercooler. (2) Elbow coolant supply to aftercooler.

The aftercooler cools the air coming out of the turbocharger before it goes 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.

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.


Turbocharger
(1) Turbocharger. (2) Cross pipe. (3) Exhaust manifolds.


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

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


NOTICE

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


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

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 intake valves.


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

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). Movement of the rocker arms makes bridges (1) move up and down on dowels mounted in the cylinder head. The bridges let one rocker arm open and close two valves (intake or exhaust). There are two intake 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.


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

Lubrication System

Engines Without BrakeSaver

The lubrication system has the following components: oil pan, oil pump, oil cooler, oil filter, oil lines to and from the turbocharger and oil passages in the cylinder block. There is also a line from the oil cooler (on the right side of the engine) down and across the oil pan, to the oil filter (on left side).


Lubrication System Components
(1) Oil supply line to turbocharger. (2) Oil return line from turbocharger. (3) Oil supply line to air compressor (on rear of engine). (4) Oil cooler. (5) Oil return line from air compressor. (6) Cover on bypass line for oil cooler. (7) Oil manifold in cylinder block. (8) Tube for oil level gauge. (9) Line from oil cooler to oil filters. (10) Inlet elbow for oil cooler. (11) Oil pan. (12) Bypass valve for oil cooler.


Lubrication System Components
(1) Oil supply line to turbocharger. (2) Oil return line from turbocharger. (3) Oil supply line to air compressor. (11) Oil pan. (13) Oil manifold in cylinder block. (14) Oil filter outlet. (15) Bypass valve for oil filters. (16) Oil filters.

Oil Flow Through The Oil Filter And Oil Cooler

With the engine warm (normal operation), oil comes from the oil pan (13) through a suction bell to the oil pump (12). The oil pump sends warm oil to the oil cooler (14) and then to the oil filters (16).

From the oil filters oil is sent to the oil manifold in the cylinder block and to the oil supply line for the turbocharger (17). Oil from the turbocharger goes back through an oil return line to the oil pan (13).

With the engine cold (starting conditions), bypass valves (11 and 15) give immediate lubrication to all components when cold oil with high viscosity causes a restriction to the oil flow through the oil cooler (14) and oil filters (16). The oil pump then sends the cold oil through the bypass valves to the oil manifold in the cylinder block and to the supply line for the turbocharger. Oil from the turbocharger (17) goes back through the oil return line to the oil pan (13).

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

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


Flow Of Oil (Engine Warm)
(1) Bore for balancer shaft. (2) To rocker arm shaft. (3) To air compressor (truck engines). (4) To fuel injection pump housing. (5) Plug (on rear left) or to fuel ratio control (on front right). (6) Rocker arm shaft. (7) To valve lifters. (8) Bore for camshaft. (9) Piston cooling tubes. (10) To timing gear housing. (11) Bypass valve for oil cooler. (12) Oil pump. (13) Oil pan. (14) Oil cooler. (15) Bypass valve for oil filters. (16) Oil filters. (17) Turbocharger.


Flow Of Oil (Engine Cold)
(11) Bypass valve for oil cooler. (12) Oil pump. (13) Oil pan. (14) Oil cooler. (15) Bypass valve for oil filters. (16) Oil filters. (17) Turbocharger.

Engines With Brakesaver


Lubrication System Components
(1) Oil supply line to turbocharger. (2) Tube for oil level gauge. (3) Oil return line from turbocharger. (4) Oil supply line to air compressor. (5) Oil return line from air compressor. (6) Oil cooler. (7) Line from oil cooler to oil filters. (8) Oil pan. (9) BrakeSaver valve.

The lubrication system has the following components: oil pan, two section oil pump, oil cooler, oil filter, oil lines to and from the turbocharger and oil passages in the cylinder block. The front section of the oil pump supplies oil for lubrication of the engine. The rear section of the oil pump supplies oil for operation of the BrakeSaver. The front section of the oil pump sends oil through the oil filter and the rear section of the oil pump sends oil through the oil cooler.

Oil Flow Through the Oil Filter

With the engine warm (normal operation), oil comes from oil pan (6) through suction bell (8) to the front section of the oil pump (7). The front section of the oil pump sends oil to oil filter (4). From the oil filter, oil is sent to oil manifold (1) in the cylinder block and to oil supply line (2) for the turbocharger. Oil from the turbocharger goes back through oil return line (3) to the oil pan.

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

When the oil gets warm, the pressure difference in the bypass valve decreases and the bypass valve closes. Now there is a normal flow through the oil filter.


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


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

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

Oil Flow Through the Oil Cooler

With the engine warm (normal operation), oil comes from oil pan (6) through suction bell (7) to the rear section of oil pump (5). The rear section of the oil pump sends warm oil to the BrakeSaver control valve (3). If the BrakeSaver control valve is in the OFF position, it sends the warm oil to oil cooler (1) where it is made cool. From the oil cooler, the cool oil goes back through the BrakeSaver control valve to engine oil pan (6).


Flow of Oil With BrakeSaver Off (Engine Warm)
(1) Oil cooler. (2) Bypass valve for the oil cooler. (3) BrakeSaver control valve. (4) BrakeSaver. (5) Oil pump (rear section). (6) Oil pan. (7) Suction bell.

If BrakeSaver control valve (3) is in the ON position, the oil from the rear section of oil pump (5) that goes to the BrakeSaver control valve is now sent to BrakeSaver (4). After the oil goes through the BrakeSaver, it goes back to the BrakeSaver control valve. The control valve now sends the warm oil to oil cooler (1) where it is made cool. From the oil cooler, the cool oil goes back through the BrakeSaver control valve to engine oil pan (6).

When the engine is cold (starting conditions), the oil has a high viscosity. This high viscosity causes a restriction to the oil flow through oil cooler (1). When there is a restriction in the oil cooler, an oil pressure difference in bypass valve (2) causes the valve to open. When the bypass valve is open, oil from the rear section of oil pump (5) can go through the valve and drain back into engine oil pan (6).


Flow of Oil with BrakeSaver On (Engine Warm)
(1) Oil cooler. (2) Bypass valve for the oil cooler. (3) BrakeSaver control valve. (4) BrakeSaver. (5) Oil pump (rear section). (6) Oil pan. (7) Suction bell.


Flow of Oil with BrakeSaver Off (Engine Cold)
(1) Oil cooler. (2) Bypass valve for the oil cooler. (3) BrakeSaver control valve. (4) BrakeSaver. (5) Oil pump (rear section). (6) Oil pan. (7) Suction bell.

Oil Flow In The Engine


Oil Flow In The Engine
(1) Bore for balancer shaft. (2) To rocker arm shaft. (3) To air compressor. (4) To fuel injection pump housing. (5) Plug (on rear left) or to fuel ratio control (on front right). (6) Rocker arm shaft. (7) To valve lifters. (8) Bore for camshaft. (9) Piston cooling tubes. (10) To timing gear housing. (11) Bore for idler gear shaft. (12) Main bearings. (13) To turbocharger. (14) From oil filters. (15) Oil manifold.

From the oil manifold (15) in one side of the cylinder block, oil is sent to the oil manifold in the other side through drilled passages in the cylinder block that connect the main bearings (12) and the bore for camshaft (8). Oil goes through drilled holes in the crankshaft to give lubrication to the nonnecting rod bearings. A small amount of oil is sent through piston cooling tubes (9) near the main bearings to make the pistons cooler. Oil goes through grooves in the bores for the front and rear camshaft bearings and then into passages (7) that connect the valve lifter bores. These passages give oil under pressure for the lubrication of the valve lifters.

Oil is sent through passages (2), on front and rear, to the rocker arm shafts (6) on both cylinder heads. Holes in the rocker arm shafts let the oil give lubrication to the valve system components in the cylinder head.

On earlier engines, the air compressor gets oil from passage (3) in the cylinder block, through the flywheel housing. On later engines, a hose assembly carries oil from manifold (15) to the air compressor and passage (3) is plugged.

The idler gear (11) gets oil from a passage in the cylinder block and in the shaft for the idler gear installed on the front of the cylinder block.

The fuel injection pump and governor gets oil from passage (4) 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. Oil for the fuel ratio control is taken from the top of the right cylinder head, at the front, at a point similar to (5) on the left cylinder head. The automatic timing advance unit gets oil from the injection pump housing, through the camshaft for the fuel injection pumps.

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

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

BrakeSaver

The BrakeSaver permits the operator to control the speed reduction of the vehicle on grades, curves, or at any time when speed reduction is necessary but long applications of the service brakes are not desired.


Engine with BrakeSaver

BrakeSaver Components


BrakeSaver Components
(1) Flywheel housing. (2) Rotor. (3) BrakeSaver housing. (4) Flywheel. (5) Crankshaft flange. (6) Ring gear plate. (7) Stator.

The BrakeSaver housing (3) is fastened directly to the rear face of flywheel housing (1). The BrakeSaver adds approximately four inches to the length of the engine drive train. A rotor (2) and a ring gear plate (6) are installed between the rear flange of crankshaft (5) and flywheel (4). The ring gear plate (6) permits the use of the standard engine starting motor. The rotor turns in a space between stator (7) and BrakeSaver housing (3).


BrakeSaver Components
(8) Oil pump (rear section). (9) BrakeSaver. (10) Tube. (11) Hole. (12) Bypass valve. (13) Baffle. (14) Oil pump (front section). (15) Engine oil pan. (16) BrakeSaver control valve. (17) Line. (18) Line.

The engine oil pump has two sections. The front section (14) of the oil pump gives oil to the engine for lubrication. Rear section (8) of the oil pump sends engine oil through BrakeSaver control valve (16) to BrakeSaver (9). The rear section of the oil pump also sends oil through line (17) to the engine oil cooler (not shown). From the oil cooler, the cool oil goes through line (18), through baffle (13) and back into engine oil pan (15).

When the BrakeSaver is turned off, tube (10) lets the oil in the BrakeSaver rapidly go out of the BrakeSaver and back into the engine oil pan.

When the engine is cold (starting conditions), the oil has a high viscosity. This high viscosity causes a restriction to the oil flow through the oil cooler. When there is a restriction in the oil cooler, an oil pressure difference in the bypass valve (12) causes the valve to open. When the bypass valve is open, oil from the rear section of the oil pump can go through hole (11) in bypass valve (12) to drain back into engine oil pan (15).

BrakeSaver Lubrication


BrakeSaver Lubrication
(1) Oil line. (2) Orifice. (3) Piston-type ring seal. (4) Orifice. (5) Chamber. (6) Piston ring seal. (7) Lip-type seal. (8) Lip-type seal. (9) Oil line.

Piston ring seals (3 and 6) keep pressure oil in chamber (5) around the rotor during operation. Lip-type seals (7 and 8) prevent oil leakage from the BrakeSaver. An outside oil line (1) from the engine lubrication system sends engine oil to the BrakeSaver housing. Orifices (2 and 4) in the BrakeSaver send oil to a space between the lip seals and the piston-type ring seals at a rate of 1.24 liter/min (.33 U.S. gpm). This oil gives lubrication to the seals under all conditions of operation.

The spaces between the lip-type seals and the piston-type seals are connected to an outside drain line (9) that lets the oil go back to the engine oil pan.

BrakeSaver Operation

In downhill operation, the crankshaft is turned by the rear wheels (through the differential, driveshaft, transmission, and clutch). To reduce the speed of the vehicle, an application of a braking force can be made to the crankshaft. The BrakeSaver does this through the conversion of the energy of rotation into heat which is removed by the engine cooling system.

The rotor (5) is fastened to and turns with the engine crankshaft. The rotor has pockets (4) on the outer circumference of both sides and four holes (3) to permit equal oil flow to both sides of the rotor.

The BrakeSaver housing (1) and the stator are fastened to the flywheel housing and can not turn. Both the BrakeSaver housing and the stator have pockets (2) on their inside surfaces in alignment with the pockets (4) in the rotor.


BrakeSaver Housing and Rotor
(1) BrakeSaver housing. (2) Pockets. (3) Hole. (4) Pocket. (5) Rotor.

The rotor (5) turns in the compartment made by stator (6) and BrakeSaver housing (1). When the BrakeSaver housing is in operation, engine oil comes into this compartment near the center through a passage from the bottom of the BrakeSaver housing. The rotor, turning with the crankshaft, throws this oil outward. As the oil flows outward, the shape of rotor pockets (4) send the oil into pockets (2) of the stator and BrakeSaver housing. As the rotor turns and the oil flows around the BrakeSaver compartment, it takes the shape of a spiral.

As the oil flows around the BrakeSaver compartment, it is constantly cut by the vanes (the material between the pockets) of the rotor. This cutting action gives resistance to the rotor and changes the energy of the rotor into heat in the oil. The heat is removed by the oil cooler and goes into the engine cooling system.


Oil Flow Through BrakeSaver
(1) BrakeSaver housing. (2) Pocket. (4) Pocket. (5) Rotor. (6) Stator.

As the BrakeSaver inlet passage opens, more oil starts to flow in a spiral shape between the rotor and the stator. Inside this spiral flow (7) of oil is an air pocket (8). As the pressure in the rotor compartment increases, the amount of oil in the spiral flow increases in thickness and the air pocket has compression. As this air pocket has compression, the amount of oil being cut by the rotor vanes has an increase.

When the BrakeSaver is in operation, the level of braking can be controlled by the inlet oil pressure, since the braking force available is in direct relation to the amount of oil that is cut by the rotor vanes. When the BrakeSaver is not in operation, the inlet passage to the rotor compartment is closed by the control valve, and there is no oil in the BrakeSaver compartment.


Oil Flow in BrakeSaver
(1) BrakeSaver housing. (5) Rotor. (6) Stator. (7) Spiral flow. (8) Air pocket.

BrakeSaver Control


BrakeSaver Oil Flow (Off)
(1) BrakeSaver control lever. (2) Oil cooler. (3) Valve spool. (4) BrakeSaver control valve. (5) Oil pump. (6) BrakeSaver. (7) Line. (8) Oil pan.

When the BrakeSaver control lever (1) is in the OFF position, spring force holds valve spool (3) against the cover at the air inlet end of control valve (4). With valve spool (3) in this position, oil pump (5) sends engine oil from oil pan (8) through control valve (4) to oil cooler (2). From the oil cooler, the oil goes through the control valve, through line (7) and back to engine oil pan (8). With the BrakeSaver control valve in this position, no oil is sent to BrakeSaver (6).

When BrakeSaver control lever (1) is moved to the ON position, pressure air moves valve spool (3) to the right against the spring force. With the valve spool in this position, engine oil from oil pump (5) is sent through control valve (4) to the rotor compartment of BrakeSaver (6). From the BrakeSaver, the oil goes through the control valve, through oil cooler (2), back through the control valve, and back into the BrakeSaver.

The oil cannot go back to engine oil pan (8) because the passage through the control valve to line (7) is closed by the valve spool.

The time required to fill the BrakeSaver with pressure oil to the point of maximum braking in the BrakeSaver is approximately 1.8 seconds.


BrakeSaver Oil Flow (Fill)
(1) BrakeSaver control lever. (2) Oil cooler. (3) Valve spool. (4) BrakeSaver control valve. (5) Oil pump. (6) BrakeSaver. (7) Line. (8) Oil pan.

As BrakeSaver (6) fills, the turning rotor causes an increase in the oil pressure in the BrakeSaver. Inlet oil to the BrakeSaver and outlet oil from the BrakeSaver both go into the spring bore in valve spool (3). The average of the inlet oil pressure and the outlet oil pressure in the spring bore plus the force of the spring work against the pressure air on the left end of the valve spool. When the force of the pressure oil plus the spring force become larger than the force of the pressure air, the valve spool moves to the left. This movement causes a restriction in the passage for the inlet oil and an oil pressure decrease in the BrakeSaver.

A decrease in rotor speed (normally with a decrease in vehicle speed) causes a decrease in the oil pressure in the BrakeSaver. This causes a decrease in oil pressure in the spring bore of the valve spool which lets the pressure air on the left end of the spool move the spool to the right. This movement opens the passage for the inlet oil and the oil pressure in the BrakeSaver has an increase.


BrakeSaver Oil Flow (Operate)
(1) BrakeSaver control lever. (2) Oil cooler. (3) Valve spool. (6) BrakeSaver. (8) Oil pan.

An increase in rotor speed will cause an increase in the oil pressure in the BrakeSaver. This increase in oil pressure will cause the valve spool to move to the left to give a restriction to the inlet oil to the BrakeSaver.

The valve spool is constantly moving to make adjustments to the BrakeSaver inlet pressure for compensation of the changing rotor speeds caused by normal operation of the vehicle. This constant movement of the valve spool is necessary to keep the amount of braking force in the BrakeSaver at the level set by control lever (1).

During normal operation, the outlet oil from the BrakeSaver goes to oil cooler (2). From the oil cooler, some of the oil (approximately 60%) goes back to the BrakeSaver inlet and the remainder of the oil from the oil cooler goes to engine oil pan (8).

When BrakeSaver control lever (1) is moved to the OFF position, the pressure air on the left end of valve spool (3) goes out of control valve (4). With no pressure air in the valve, the pressure oil in the spring bore plus the spring force move the valve spool against the cover at the air inlet end of the control valve. This movement closes the BrakeSaver inlet passage. The rotor in BrakeSaver (6) now pushes the oil out of the BrakeSaver, through the control valve, through line (9), and back to oil pan (8).

The time required to remove the oil from the BrakeSaver is approximately 1.5 seconds.

With the control valve in this position, oil pump (5) sends oil through oil cooler (2) and through line (7) back to the oil pan.


BrakeSaver Oil Flow (Drain)
(1) BrakeSaver control lever. (2) Oil cooler. (3) Valve Spool. (4) BrakeSaver control valve. (5) Oil pump. (6) BrakeSaver. (7) Line. (8) Oil pan. (9) Line.

Operator Controls

Two types of controls are available for the BrakeSaver: a manual control and an automatic control.

Manual Control

Pressure air from the truck air system is sent to pressure reducing valve (1) where the air pressure is controlled to 345 kPa (50 psi). This controlled pressure air goes to manual control valve (2).

When the operator moves BrakeSaver control lever (3) toward the ON position, pressure air is sent to BrakeSaver control valve (6). The farther lever (3) is moved toward the ON position, the higher the pressure of the air sent to the BrakeSaver control valve. An increase in air pressure in the BrakeSaver control valve causes an increase in the oil pressure in the BrakeSaver. An increase in the oil pressure in the BrakeSaver causes an increase in the braking force in the BrakeSaver. The operator can give modulation to the braking force in the BrakeSaver through the movement of BrakeSaver control lever (3).

When the BrakeSaver is turned off, the pressure air goes out of the system through a passage in manual control valve (2). This lets the pressure air out of BrakeSaver control valve (6) and removes the braking force from the BrakeSaver.

An air pressure passage gauge (4) gives the operator a relative indication of the air pressure being sent to the BrakeSaver control valve. Through the use of the indication on the air pressure gauge in relation to engine rpm, the operator can get approximately the same braking effect from the BrakeSaver time after time. This lets the operator more easily control the desired wheel speed of the vehicle.

An oil temperature gauge (5) gives the operator an indication of the ability of the engine cooling system to control the heat in the BrakeSaver during its operation. If the gauge reads too HOT, move BrakeSaver control lever (3) to the OFF position and use the service brakes to control the wheel speed of the vehicle. With the BrakeSaver off, the oil temperature will rapidly become normal again and the BrakeSaver can be used.


NOTICE

Do not manually engage the BrakeSaver and control the wheel speed with the accelerator. The design of the cooling system is for the control of the temperature of the oil at full engine power or full BrakeSaver capacity, but not both at the same time.



Manual Control Diagram
(1) Pressure reducing valve. (2) Manual control valve. (3) BrakeSaver control lever. (4) Air pressure gauge. (5) Oil temperature gauge. (6) BrakeSaver control valve.

Automatic Control


Automatic Control
(1) Pressure reducing valve. (2) Manual control valve. (3) BrakeSaver control lever. (4) Air pressure gauge. (5) Oil temperature gauge. (6) BrakeSaver control valve. (7) Double check valve. (8) Solenoid valve. (9) Key switch. (10) Mode selector switch. (11) Accelerator switch. (12) Clutch switch.

All the components of the manual control are in the automatic control and their functions are the same. In the automatic control, there is also a solenoid valve (8), al double check valve (7), and three switches (10), (11) and (12). The solenoid valve (8) (when activated) sends pressure air from the pressure reducing valve (1) to the BrakeSaver control valve (6). The solenoid valve is connected to three switches: mode selector switch (10), accelerator switch (11), and clutch switch (12). The switches are connected to each other in series (all switches must be closed to activate the solenoid). The source of electric current is from the key switch (9) which prevents the solenoid valve from being activated when the key switch is OFF.

The mode selector switch (10) has two positions: MANUAL and AUTOMATIC-MANUAL. For automatic operation of the BrakeSaver, the mode selector switch must be in the AUTOMATIC-MANUAL position.

The clutch switch (12) is connected to the clutch linkage. When the clutch is engaged (clutch pedal up), the switch is closed. For automatic operation of the BrakeSaver, the clutch switch must be CLOSED (pedal up).

NOTE: In vehicles with no clutch pedal, the clutch switch is removed from the circuit.

The accelerator switch (11) is installed in the governor. When the accelerator is released (accelerator pedal up), the switch is closed. For automatic operation of the BrakeSaver, the accelerator switch must be closed (accelerator pedal up).

When the switches are closed, the electric current from key switch (9) opens solenoid valve (8). When the solenoid valve is open, full air pressure [345 kPa (50 psi)] is sent through double check valve (7) to BrakeSaver control valve (6). The double check valve keeps the pressure air from going out of the system through manual control valve (2) when the BrakeSaver control lever (3) is not in use. It also keeps the pressure air from going out of the system through solenoid valve (8) when the manual control is in use.

Because the solenoid valve sends full air pressure to the BrakeSaver control valve, there is no modulation in the AUTOMATIC-MANUAL position.

When the mode selector switch (10) is in the AUTOMATIC-MANUAL position and the accelerator pedal is released (pedal up), the BrakeSaver is operating at its maximum capacity. When the clutch is released (pedal down) the BrakeSaver goes off. When the clutch is engaged again (pedal up), the accelerator pedal turns the BrakeSaver off and lets the vehicle run freely. More pressure on the accelerator pedal sends fuel to the engine.

When the BrakeSaver is turned off, the pressure air goes out of the system through a passage in manual control valve (2) or in solenoid valve (8). This lets the pressure air out of BrakeSaver control valve (6) and removes the braking force from the BrakeSaver.

The manual control valve (2) can be operated with mode selector switch (10) in the AUTOMATIC-MANUAL position. During normal operation, the solenoid valve will send full air pressure to the BrakeSaver control valve and remove the effect of the manual control valve. If there is a failure in the electric system when the mode selector switch is in the AUTOMATIC-MANUAL position, the BrakeSaver can be controlled with the manual control valve.

Cooling System


Cooling System Schematic
(1) Turbocharger. (2) Aftercooler. (3) Vent line. (4) Outlet from temperature regulator housing to radiator top (one on each side of the engine front. (5) Temperature regulator housing (both sides). (6) Radiator. (7) Outlet bonnet of oil cooler. (8) Shunt line. (9) Oil cooler. (10) Line to aftercooler. (11) Inlet bonnet of oil cooler. (12) Water pump. (13) Water pump inlet, from radiator bottom. (14) Radiator bypass lines.

When the temperature regulators are fully closed (engine cold), no water goes through the outlets (4) to the radiator. All the water flows directly to the water pump (12) through both radiator bypass lines (14). Some water can go to the radiator top tank through the vent line (3), but it does not flow through the radiator core because the shunt line (8) returns that water directly to the pump.

When the temperature regulators are fully open (engine warm), a small amount of water goes through the two radiator bypass lines (14). Most of the water flows through the radiator core.

One engines without aftercooler, the line (10) becomes an oil cooler bypass line, and it will connect to the outlet bonnet (7) of the oil cooler. Part of the water will flow through the oil cooler (9), and part will flow through the bypass line (10). From the outlet bonnet (7) all the water will flow into the cylinder block and then to both cylinder heads.


Cooling System Components
(1) Turbocharger. (2) Aftercooler. (4) Outlet to radiator top. (5) Temperature regulator housing. (7) Outlet bonnet of oil cooler. (9) Oil cooler. (10) Line to aftercooler. (11) Inlet bonnet of oil cooler. (12) Water pump. (13) Water pump inlet, from radiator bottom. (14) Radiator bypass line.

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 cylinders 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 air compressor. There is a constant flow of coolant through the element.

The element has a specific amount of inhibitor for acceptable cooling system protection. As coolant flows through the element, the corrosion inhibitor, which is a dry material, dissolves (goes into solution) and mixes to the correct concentration. Two basic types of elements are used for the cooling system, and they are called the "PRECHARGE" and the "MAINTENANCE" elements. Each type of element has a specific use and must be used correctly to get the necessary concentration for cooling system protection. The 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 (unless Dowtherm 209 Antifreeze is used). This element has to add enough inhibitor to bring the complete cooling system up to the correct concentration.

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


NOTICE

Do not use Dowtherm 209 Full-Fill in a cooling system that has a coolant conditioner. These two systems are not compatible (corrosion inhibitor is reduced) when used together.


Basic Block

Cylinder Block, Heads And Liners

The cylinder block is a 65° vee. A steel spacer plate is used between the cylinder heads and the block to eliminate liner counterbore and to provide maximum liner flange support area (the liner flange sits directly on the cylinder block).

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

This engine uses a single cast head for each side.

Pistons, Rings And Connecting Rods

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

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

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

The prechamber piston uses a partial skirt and has a steel heat plug mounted in the pocket (crater) on top of the piston. This plug protects the top of the piston from erosion and burning.

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

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

Crankshaft

The crankshaft changes the combustion forces in the cylinder into usable rotating torque which powers the machine. A vibration damper is used at the front of the crankshaft to reduce torsional vibrations. The vibration damper can be of the fluid type or can be made of a flywheel ring and an inner hub, connected together by a rubber ring.

There is a gear at the front of the crankshaft to drive the timing gears and the oil pump. Lip 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.

Camshaft

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

A gear on the rear of the camshaft is used to drive the balance gear and any accessory equipment mounted on the rear of the engine.

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 starting circuit of a "PC" engine can have a glow plug for each cylinder. Glow plugs are small heating units in the precombustion chambers. Glow plugs make ignition of the fuel easier when the engine is started in cold temperature.

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.


NOTICE

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


Charging System Components

Alternator (Delco-Remy)

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

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

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

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


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

Starting System Components

Solenoid

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

a. Closes the high current starter motor circuit with a low current start switch circuit.
b. Engages the starter motor pinion with the ring gear.


Typical Solenoid Schematic

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

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

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

Starter Motor

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


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

The starter 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 starter pinion, by a mechanical linkage, to engage with the ring gear on the flywheel of the engine. The starter pinion will engage with the ring gear before the electric contacts in the solenoid close the circuit between the battery and the starter motor. When the circuit between the battery and the starter motor is complete, the pinion will turn the engine flywheel. A clutch gives protection for the starter motor so that the engine, when it starts to run, can not turn the starter motor too fast. When the start switch is released, the starter 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 completes the electric circuit through the circuit breaker. If the current in the electrical system gets too high, it causes the metal disc to get hot. This heat causes a distortion of the metal disc which opens the contacts and breaks the circuit. A circuit breaker that is open can be reset after it cools. Push the reset button to close the contacts and reset the circuit breaker.


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

Caterpillar Information System:

3408 & 3408B DIESEL TRUCK ENGINE Series Parallel Switches
3408 & 3408B DIESEL TRUCK ENGINE Glow Plugs
3408 & 3408B DIESEL TRUCK ENGINE Starter Motor Solenoids
3408 & 3408B DIESEL TRUCK ENGINE Starter Motors
3408 & 3408B DIESEL TRUCK ENGINE Alternators
3408 & 3408B DIESEL TRUCK ENGINE Brakesaver Control Valve<BR> (9N29, 9N3686, 9N3687)
3408 & 3408B DIESEL TRUCK ENGINE BrakeSaver (9N2125)
3408 & 3408B DIESEL TRUCK ENGINE Flywheel Runout
3408 & 3408B DIESEL TRUCK ENGINE Flywheel Adapter Group (6N9829) (Not For Use With BrakeSaver)
3408 & 3408B DIESEL TRUCK ENGINE Flywheel - For Use With BrakeSaver<BR> 9N678 Flywheel Group
3408 & 3408B DIESEL TRUCK ENGINE Flywheel - For Use Without BrakeSaver<BR> 9N676 Flywheel Group
3408 & 3408B DIESEL TRUCK ENGINE Flywheel Housing Runout<BR> Face Runout (axial eccentricity) of the Flywheel Housing:
3408 & 3408B DIESEL TRUCK ENGINE Testing and Adjusting
3408 & 3408B DIESEL TRUCK ENGINE Introduction
3408 & 3408B DIESEL TRUCK ENGINE Troubleshooting Problem List
3408 & 3408B DIESEL TRUCK ENGINE Troubleshooting Problems
3408 & 3408B DIESEL TRUCK ENGINE BrakeSaver Troubleshooting
3408 & 3408B DIESEL TRUCK ENGINE Engine Vibration Troubleshooting
3408 & 3408B DIESEL TRUCK ENGINE General Instructions
3408 & 3408B DIESEL TRUCK ENGINE Turbocharger
3408 & 3408B DIESEL TRUCK ENGINE Turbocharger (Airesearch TV8103)
3408 & 3408B DIESEL TRUCK ENGINE Turbocharger (Schwitzer 4MF)
3408 & 3408B DIESEL TRUCK ENGINE Aftercooler
3408 & 3408B DIESEL TRUCK ENGINE Air Compressor
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