General Information

The 1673C Engine is a 638 cu. in. (10,5 liters) displacement, 4-stroke cycle, six cylinder, turbocharged, diesel engine. The cylinder bore is 4.75 in. (120,6 mm) and the piston stroke is 6.00 in. (152,4 mm). The firing order is 1-5-3-6-2-4. The engine weighs approximately 1940 lbs. (880 kg) without coolant or oil.

Inlet air filtered by a dry-type air cleaner, is compressed by a turbocharger before entering the engine cylinders. The turbocharger is driven by the engine exhaust.

A plunger and barrel-type fuel injection pump meters and pumps filtered fuel to a precombustion chamber for each cylinder. The fuel is delivered to the precombustion chamber under high pressure. Injection for each cylinder begins before the piston reaches top center on the compression stroke.

A hydra-mechanical governor controls the fuel injection pump out-put to maintain a constant engine RPM under varying work loads. When the engine is being started, a speed limiting device in the governor limits engine speed until engine oil pressure builds up to a safe operating pressure.

The engine is of overhead valve design, having one inlet and one exhaust valve for each cylinder. The camshaft, geared and timed to the crankshaft, actuates rocker arms and valves through mechanical lifters and push rods.

The timing gears are located on the front of the engine.

The starting system is direct electric and uses a 24-volt starting motor. A 12-volt starting motor is optional.

Engine coolant is used to cool the engine lubricating oil. A full-flow temperature regulator, in the cylinder head at the front of the engine, provides for quick engine warm-up, and allows free circulation of coolant after operating temperature has been reached.

Lubrication for the engine is supplied by a gear-type pump. The pump provides full pressure lubrication to the engine internal and external parts.

The lubricating oil is both cooled and filtered. Bypass valves in the oil cooler assembly provide unrestricted flow of lubricating oil to the engine parts when oil viscosity is high or, if either the oil cooler or the oil filter element should become clogged.

Fuel System

FUEL SYSTEM SCHEMATIC

The fuel system is a pressure-type with a separate injection pump for each engine cylinder. The engine driven gear-type fuel transfer pump draws fuel from the tank through a primary fuel filter. The transfer pump forces the fuel, from the tank, through the main fuel filter. The capacity of the fuel transfer pump is so great that a bypass valve controls the pressure of the fuel. The excess fuel through the bypass valve returns to the fuel tank.

The controlled pressure fuel from the main filter fills the fuel manifold in the fuel injection pump housing. The fuel in the manifold supplies the fuel injection pumps. Each fuel injection pump meters and forces the fuel, at the correct instant, through a line to the fuel injection valve in the precombustion chamber of the engine cylinder. The pressure of the fuel in the line opens the fuel injection valve which atomizes the fuel entering the precombustion chamber. The piston compressed air in the engine cylinder ignites the fuel spray.

Fuel Injection Pumps

Fuel manifold (1) supplies filtered fuel from the fuel transfer pump through each inlet port (2) to each injection pump.

The fuel injection pumps, one for each engine cylinder, are installed in the fuel injection pump housing. A camshaft (9), in the housing, is timed with and driven by the engine crankshaft. The camshaft lobes, one for each injection pump, operate lifter (8) and pump plunger (5) in each injection pump. A spring (6) on each lifter forces the lifter against a camshaft lobe.

FUEL INJECTION PUMP HOUSING AND PUMP CROSS SECTION
1-Fuel manifold. 2-Inlet port. 3-Check valve. 4-Gear. 5-Pump plunger. 6-Spring. 7-Fuel rack. 8-Lifter. 9-Camshaft.

A gear (4) locked on each pump plunger (5) is in mesh with fuel rack (7). The movement of the fuel rack rotates the gears and pump plungers which meter and inject the fuel into the engine cylinders. The engine governor controls the movement of fuel rack (7).

Fuel Injection Valves

A fuel injection valve in each precombustion chamber (8) for each engine cylinder atomizes the fuel, from the fuel injection pumps, so the fuel sprays into the precombustion chamber.

FUEL INJECTION VALVE IN PRECOMBUSTION CHAMBER
1-Fuel line connector nut. 2-Seal. 3-Valve assembly body. 4-Valve installation nut. 5-Seal. 6-Nozzle assembly valve. 7-Glow plug. 8-Precombustion chamber.

Glow Plugs

Glow plugs are used to help ignite the fuel when an engine is started in cold temperatures. Glow plug (7), in each precombustion chamber (8) is an electric heating element. Turning the heat switch ON for approximately a minute, before starting the engine, will heat each glow plug. The compression in the engine cylinders plus the high temperature of the glow plugs promotes easy engine starting in cold temperatures.

Governor

The accelerator pedal is linked to the control lever on the engine governor. The operation of the governor controls the amount of fuel necessary for the engine to maintain the accelerator selected engine RPM even when the load changes.

The hydra-mechanical governor has engine driven governor weights (12), governor spring (5), a hydraulic valve (13) and piston (14). The valve and piston are connected to rack (17) in the fuel injection pump housing. The engine lubricating oil pump supplies pressure oil through passage (16) and around sleeve (15) for the hydraulic operation of the governor. The accelerator pedal controls only the compression of governor spring (5). The compressed spring force always pushes to increase the supply of fuel to the engine while the centrifugal force of the engine driven governor weights are always pulling to decrease fuel to the engine. The governed RPM of the engine is when these two forces balance.

HYDRA-MECHANICAL GOVERNOR (Typical Example)
1-Collar. 2-Speed limiter plunger. 3-Lever assembly. 4-Seat. 5-Governor spring. 6-Thrust bearing. 7-Oil passage. 8-Drive gear (weight assembly). 9-Cylinder. 10-Bolt. 11-Spring seat. 12-Weights. 13-Valve. 14-Piston. 15-Sleeve. 16-Oil passage. 17-Fuel rack. The governor valve is shown in the position when the force of the weights and the force of the spring are balanced.

When engine load increases, engine RPM decreases and revolving weights (12) slow down. The weights move toward each other and allow governor spring (5) to move valve (13) forward. As valve (13) moves, an oil passage around valve (13) opens to pressure oil. Oil then flows through passage (7) and fills the chamber behind piston (14). The pressure forces the piston and rack forward, increasing the amount of fuel to the engine. Engine RPM increases until the revolving weights rotate fast enough to balance the force of the governor spring.

When engine load decreases, engine RPM increases, revolving weights (12) speed-up, and the toes on the weights move valve (13) rearward, allowing the oil behind piston (14) to flow through a drain passage opened at the rear of the piston. At the same time, the pressure oil between sleeve (15) and piston (14) forces the piston and rack rearward, decreasing the amount of fuel to the engine. Engine RPM decreases until the revolving weights balance the force of the governor spring.

When the engine is started, speed limiter plunger (2) restricts the movement of the governor control linkage. When operating oil pressure is reached, the plunger in the speed limiter retracts and the governor control can be moved to the HIGH IDLE position.

When the engine RPM is at LOW IDLE, a spring-loaded plunger within the lever assembly in the governor bears against the shoulder of the low idle adjusting screw. To stop the engine, the plunger must be forced past the shoulder on the adjusting screw.

Oil from the engine lubricating system lubricates the governor weight bearing. The various other parts are splash lubricated. The oil from the governor drains into the fuel injection pump housing.

Fuel Ratio Control

Fuel ratio control bolt (7) is connected by a slot in collar (3) and bolt (4) through the engine governor to the fuel injection pump rack. An air line from the engine inlet manifold supplies manifold pressure air to the chamber inside cover (5).

When the engine is accelerated, or the load on the engine increases, bolt (7) in collar (3) restricts the movement of the fuel rack until the turbocharged boost of air in the inlet manifold and inside the fuel ratio control cover (5) forces diaphragm (2) to compress spring (6). Compressing spring (6) moves bolt (7) which relieves the restriction from collar (3) and the fuel rack. This allows the fuel rack to increase the fuel as the turbocharged air pressure increases with the increase in engine RPM. The compressed force of spring (1) can be adjusted if it is necessary to correct the fuel-to-air ratio.

FUEL RATIO CONTROL-CROSS SECTION
1-Spring. 2-Diaphragm. 3-Collar. 4-Bolt. 5-Cover. 6-Spring. 7-Bolt.

Air Induction And Exhaust

A turbocharger is in the engine air induction and exhaust system. The turbocharger is driven by the exhaust from the engine cylinders and has no mechanical connection with the engine.

The turbocharger compressor impeller wheel (5) is connected to the turbine wheel (6) shaft. The exhaust gases in exhaust manifold (1) enter the turbocharger and pass through the blades of turbine (6) forcing the turbine and compressor impeller (5) to rotate at high RPM. The rotating compressor impeller draws air through the engine air cleaner, through compressor air inlet (4) and then forces this filtered air into engine inlet manifold (2). The volume of air forced into the engine inlet manifold raises the pressure of the air in the manifold. The high pressure of the air in the inlet manifold charges the engine cylinders with super amounts of air.

AIR INDUCTION AND EXHAUST SYSTEM-SCHEMATIC
1-Engine exhaust manifold. 2-Engine air inlet manifold. 3-Engine cylinder. 4-Turbocharger air inlet. 5-Compressor impeller wheel. 6-Turbine wheel. 7-Turbocharger exhaust outlet.

The turbocharger is mounted directly on the engine exhaust manifold and all of the exhaust gases from the engine cylinders must pass through the turbocharger. The rotating speed of the turbocharger turbine and compressor impeller is directly relevant to the engine RPM and load. When the engine load increases, more fuel is supplied to the engine cylinders. This increases the volume of the exhaust gases through the turbocharger turbine blades and the turbine and compressor impeller rotate faster. With increased compressor impeller rotating speed, a greater volume of air is drawn through the engine air cleaner and forced into the engine inlet manifold. As the turbocharger supplies more air to the engine, more fuel is burned and the engine produces more horsepower.

The safe maximum turbocharger turbine rotating speed allowed is in direct relation to the altitude at which the engine is operated. The turbine rotating speed is controlled by the fuel injection pump rack setting and the engine governor high idle RPM setting. The governor RPM and rack settings are not the same for all altitudes.

When the engine is to be operated at a higher altitude than specified, the settings must be changed. The fuel injection pump rack and governor are set for a particular altitude operation by personnel qualified to make these settings.

Wire seals on both the governor and turbocharger are to prevent unqualified personnel from tampering with the settings of the fuel pump rack and governor.

The engine can be operated at a lower altitude than specified without any danger of engine damage. In this situation, the engine performance is less than the maximum performance for the lower altitude. If the engine will not return to the higher altitude, a qualified serviceman can change the settings to obtain maximum engine performance at the lower altitude.

Turbocharger Lubrication

The turbocharger is pressure-lubricated by engine lubricating oil whenever the engine is operating. The engine lubricating oil pump forces the oil through the oil filter and through a line connected to the top of the turbocharger center section.

TYPICAL TURBOCHARGER CROSS SECTION
1-Compressor impeller wheel. 2-Thrust bearing. 3-Lubricating oil inlet port. 4-Turbine wheel (and shaft). 5-Compressor housing. 6-Oil drain port. 7-Bearings. 8-Turbine housing.

Passages leading from lubricating oil inlet port (3) on top of the center section direct the oil to lubricate thrust bearing (2) and bearings (7) in the turbocharger. The lubricating oil drains from the turbocharger through port (6) and through a line leading to the oil sump in the engine oil pan.

Lubrication System

ENGINE LUBRICATION SYSTEM-CUTAWAY

The timing gears, at the front of the engine, drive the gear-type lubricating oil pump. The pump draws oil from the lubricating oil sump, through a screen in the suction bell in the engine oil pan, and pumps the oil to the base of the oil cooler. The pressure of the oil from the pump is controlled by a regulating valve in the oil pump body. When the engine is operating normally, bypass valves for the oil cooler and oil filter are closed and the hot lubricating oil passes through the oil cooler, through the oil filter and then to the engine oil manifold. The bypass valve in the oil cooler base is open to the oil filter only if there is a restriction in the cooler or if the viscosity of the oil is too low (cold oil has low viscosity). The oil filter bypass valve is open to the engine manifold only if the oil filter restriction is too high or the viscosity of the oil is too low.

The oil in the engine manifold is directed to the turbocharger, the timing gear bearings, the rocker arm shaft bearings in the cylinder head and to the crankshaft main bearings. The oil from the main bearings is forced through oil passages in the crankshaft main bearing journals which lead to the connecting rod bearing journals. Oil spray orifices, near the crankshaft main bearings, spray lubricating oil on the underside of the piston pin bearings in the pistons and connecting rods. The oil spray also lubricates the piston rings and the cylinder walls.

The lubricating oil from the rocker arm shaft bearings and rocker arms drains onto the valve stems and down the push rods to the cam followers (valve lifters), the cam lobes and into the intermediate and rear camshaft bearings.

Oil passages from the oil manifold in the cylinder block also lead to the fuel injection pump housing. The oil passages in the pump housing direct the pressure oil to the injection pump camshaft rear bearing and to the governor drive gears. The passage to the camshaft rear bearing also leads to the governor hydraulic valve to operate the governor. The oil drains from the governor housing through a passage in the injection pump housing mount and into the cylinder block. The level of the oil in the sump, in the bottom of the injection pump housing, lubricates the intermediate and camshaft front bearings. The other components in the fuel injection pump housing are splash lubricated by the camshaft lobes as they rotate through the oil in the housing sump. A drain passage in the front flange of the injection pump housing maintains the level of the oil sump. The oil draining through the passage in the housing flange passes through the accessory drive housing and lubricates the bearing in the accessory drive gear in the timing gear housing. The bearings in all of the timing gears, except the accessory drive gear bearings, are pressure lubricated from the oil in the manifold in the cylinder block.

After lubricating the engine, the oil drains down into the sump in the oil pan. The lubricating oil continually circulates from the oil sump through the oil cooler, the oil filter and the engine and back into the sump in the oil pan whenever the engine is operating.

Cooling System

A centrifugal-type gear driven water pump (6) circulates the coolant through the engine. The pump draws coolant from the bottom of the radiator and circulates it through engine lubricating oil cooler (4) and into the engine cylinder block (9). The coolant in the block flows around the cylinder liners and up through water directors into cylinder head (3). The directors are positioned to direct the coolant around the precombustion chambers and the exhaust chamber areas in the cylinder head. All of the coolant, through the cylinder block and head, flows to the temperature regulator located in housing (2) on the left front of cylinder head (3).

COOLING SYSTEM COMPONENTS
1-Coolant outlet (to top of radiator). 2-Temperature regulator (thermostat) housing. 3-Cylinder head. 4-Engine lubricating oil cooler. 5-Radiator coolant bypass tube. 6-Water pump. 7-Water pump inlet (from bottom of radiator). 8-Air compressor. 9-Engine cylinder block.

The temperature regulator is closed, as long as the coolant temperature is below 160° F (70° C) and the coolant flows through bypass tube (5) back to water pump (6). When the coolant temperature exceeds approximately 165° F (73° C) the temperature regulator starts to open and the coolant begins to flow out coolant outlet (1) and into the top of the radiator. When the temperature regulator is open, the water pump circulates all of the coolant through the engine and radiator.

The cooling system is pressurized for two purposes. First, it permits safe operation with coolant temperatures higher than the normal boiling point, providing a margin of cooling for intermittent high temperatures resulting from peak loads. Second, it prevents cavitation in the water pump and reduces the possibility of air or steam pockets forming in the coolant passages.

The pressure relief valve, located in the highest point in the cooling system (usually in the radiator cap), maintains the pressure in the cooling system when the engine is operating. When the coolant temperature lowers, after the engine is stopped, the valve allows enough air to enter the system to relieve the partial vacuum in the cooling system.

The air compressor, mounted on the left side of the engine, is water cooled. A tube from a fitting on the water pump outlet elbow connects to the air compressor cylinder block. A tube from the air compressor head connects to the diesel engine cylinder head to complete the coolant circuit through the air compressor.

Shunt-Type Cooling System

A shunt-type cooling system for the engine is recommended. A shunt-type cooling system radiator has a normal top tank (9) above the radiator core (10) and an expansion tank (2) above (any location) the top tank.

An air and coolant tube (7) allows excess air and coolant in the radiator top tank to flow into the expansion tank. The expansion tank has a shunt line (3) which connects to the water pump (11) inlet. The shunt system maintains a positive head of coolant at the pump inlet to prevent cavitation in the pump under all operating conditions.

When initially filling the cooling system, the coolant in expansion tank (2) flows through shunt line (3) to the water pump inlet, flows through pump (11), and fills engine cylinder block (13) from the bottom. Coolant flowing into the bottom of the block forces the air out through the top of temperature regulator housing (4), through tube (7) into expansion tank (2).

It is a good procedure, after filling the system, to immediately start the engine and make certain the cooling system is full after a few minutes of engine operation. The operating water pump circulates the coolant through the engine, to drive out any air that could have been trapped in the engine. It may be necessary to add more coolant to fill the system.

SHUNT-TYPE RADIATOR COOLING SYSTEM-SCHEMATIC (Temperature regulator partially open)
1-Radiator cap (pressure regulating valve). 2-Expansion tank. 3-Shunt line tube. 4-Temperature regulator (thermostat) housing. 5-Cylinder liners (six). 6-Cylinder head. 7-Air and coolant bleed tube (between radiator top tank and expansion tank). 8-Radiator coolant bypass tube. 9-Radiator top tank. 10-Radiator core. 11-Water pump. 12-Engine lubricating oil cooler. 13-Cylinder block.

Cylinder Head

CYLINDER HEAD-END VIEW
1-Precombustion chamber (six). 2-Spring (twelve). 3-Lock (twenty four). 4-Rotocoil assembly (twelve). 5-Rocker arm (twelve). 6-Push rod (twelve). 7-Air inlet manifold (in head). 8-Valve seat insert (six inlet, six exhaust). 9-Valve (six inlet, six exhaust).

This overhead valve (OHV) cylinder head has one inlet and one exhaust valve for each engine cylinder. Rocker arms (5) are operated by the camshaft, in the engine cylinder block, cam followers (lifters) and push rods (6) which open and close valves (9) at the proper time. Each rocker arm has an adjustable contact to obtain the recommended valve lash (valve clearance). Each valve spring (2), to close a valve, is retained by locks (3) and a rotocoil assembly (4). The rotocoil will rotate a valve stem approximately one third of a degree each time the valve opens and closes. This will rotate the valve about one revolution per minute when the engine is operating at full load RPM.

The valve bushings (guides) and valve seat inserts (8) can be removed, if necessary, and new ones installed. The valve seats are ground at 30° angles. The high heat resistant steel inlet valves and stellite exhaust valves are gound slightly less (about one fourth of a degree) than 30° angles. The interference angles between the valves and valve seats provide for better seating for longer periods of time.

The inlet manifold (7) is a passage in the cylinder head casting. The exhaust manifold is bolted to the cylinder head.

Electrical System

A vehicle electrical system is actually three systems. The three systems are the engine starting system, the battery charging system and the electrical load system. The battery or batteries are common to all three systems.

Starting System

The starting system operates to start the engine when the starter switch is held closed. The system components are the battery, conductors (wires), a starting motor, glow plugs and a switch that can be positioned to close or open the circuit to the glow plugs and starting motor with the battery.

STARTING MOTOR-CROSS SECTION

The glow plugs in the starting system, one glow plug in each cylinder precombustion chamber, are cold weather starting aids. The glow plugs are heating elements and are actuated by a HEAT-START switch. The glow plugs can heat the precombustion chambers and promote diesel fuel combustion. When the switch is held in HEAT position the glow plugs attain "red hot" temperatures in approximately two minutes. The glow plugs are also actuated when the switch is moved to START position to keep the glow plugs hot while the engine is being started.

Charging System

The charging system is in operation whenever the engine is running.

The charging system components are the battery charger (either an alternator or a generator), the wires, a voltage regulator (either an alternator regulator or a generator regulator), an ammeter and sometimes a voltmeter, and the battery (batteries).

The power output (voltage) of the alternator or the generator would increase with the increase in engine speed (RPM) except the regulator in the charging circuit limits this increase in voltage. The voltage is limited to just above battery voltage. When the alternator or generator output voltage is higher than battery voltage the electric flow to the battery charges the battery.

ALTERNATOR-CUTAWAY

ALTERNATOR REGULATOR
1-Plug (over voltage limit adjusting screw. 2-Wire assembly connector.

Load System

The electrical load, usually connected through the ammeter to indicate the amount of load on the battery, can be electric lights, heaters, motors, a radio, an air conditioner and many other electrical conveniences that require battery power. The combined electric load can be so great that the engine must be operating and the combined power of the alternator or generator and the battery is needed to supply the necessary power for the load.

A disconnect switch is necessary in the electric system to open the battery circuit when the vehicle engine is not operating.

Wiring Diagrams

Because of the variations in vehicle electrical systems, some with positive and others with negative ground, some with an alternator others with a generator, and systems with many types of electric loads, a wiring diagram for all vehicles would be literally impossible to illustrate.

The large wiring diagram illustration is of a typical 12 volt system with negative ground, a 12 volt alternator and regulator and a 24 volt starting motor with a series-parallel switch to use two 12 volt batteries in series to produce the 24 volts for the starting motor.

The smaller wiring diagram is of only a 12 volt starting system. The charging and load system for this diagram would be the same as the charging and load system shown in the TYPICAL 12 VOLT SYSTEM WITH NEGATIVE GROUND wiring diagram.

12 VOLT STARTING SYSTEM (With Negative Ground)

TYPICAL 12 VOLT SYSTEM WITH NEGATIVE GROUND