Engine Oil Cooler Engine Oil Filters Engine Oil Pump Bypass Valve Engine Oil Renewal System Solenoid To Fuel Tank Scavenge Pump
Fuel System
The fuel tank is located on the left side of the truck. Fuel is pulled from the tank through the fuel heater (not shown), if equipped, and through the primary fuel filter (1) by the fuel transfer pump located on the right side of the engine behind the engine oil pump.
A fuel level sensor (2) is also located on the fuel tank. The fuel level sensor emits an ultrasonic signal that bounces off a metal disk on the bottom of a float. The time it takes for the ultrasonic signal to return is converted to a Pulse Width Modulated (PWM) signal. The PWM signal changes as the fuel level changes. The fuel level sensor provides the input signals to the VIMS, which informs the operator of the fuel level. A category level 1 warning (FUEL LVL LO) is shown on the VIMS display if the fuel level is less than 15%. A category level 2 warning (FUEL LVL LO ADD FUEL NOW) is shown on the VIMS display if the fuel level is less than 10%.
The fuel level sensor receives 24 Volts from the VIMS. To check the supply voltage of the sensor, connect a multimeter between Pins 1 and 2 of the sensor connector. Set the meter to read "DC Volts."
The fuel level sensor output signal is a Pulse Width Modulated (PWM) signal that varies with the fuel level. To check the output signal of the fuel level sensor, connect a multimeter between Pins 2 and 4 of the fuel level sensor connector. Set the meter to read "Duty Cycle." The duty cycle output of the fuel level sensor should be approximately 6% at 0 mm (0 in.) of fuel depth and 84% at 2000 mm (78.8 in.) of fuel depth.
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Fuel flows from the transfer pump (1) through the Engine ECM to the secondary fuel filters located on the left side of the engine.
The fuel transfer pump contains a bypass valve (2) to protect the fuel system components from excessive pressure. The bypass valve setting is 860 kPa (125 psi), which is higher than the setting of the fuel pressure regulator.
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The secondary fuel filters and the fuel priming pump (1) are located above the engine oil filters on the left side of the engine. The fuel priming pump is used to fill the filters after they are changed.
Fuel filter restriction is monitored with a fuel filter bypass switch (2) located on the fuel filter base. The fuel filter bypass switch provides an input signal to the Engine ECM. The ECM provides a signal to the VIMS, which informs the operator if the secondary fuel filters are restricted.
If fuel filter restriction exceeds 138 kPa (20 psi), a fuel filter restriction event is logged. No factory password is required to clear this event.
Fuel flows from the fuel filter base through the Electronic Unit Injection (EUI) fuel injectors (see Visual No. 60), the fuel pressure regulator, and then returns to the fuel tank. The injectors receive 4 1/2 times the amount of fuel needed for injection. The extra fuel is used for cooling.
NOTE: If the fuel system requires priming, it may be necessary to block the fuel return
line during priming to force the fuel into the injectors.
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Fuel flows from the fuel filter base through the steel tubes (1) to the EUI fuel injectors. Return fuel from the injectors flows through the fuel pressure regulator (2) before returning to the fuel tank. Fuel pressure is controlled by the fuel pressure regulator.
Fuel pressure should be 482 + 138 - 103 kPa (70 + 20 - 15 psi) at Full Load rpm.
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Fuel is pulled from the tank through a fuel heater, if equipped, and sent through the primary fuel filter by the fuel transfer pump. Fuel flows from the transfer pump through the Engine ECM to the secondary fuel filters.
Fuel flows from the fuel filter base through the fuel injectors in the cylinder heads. Return fuel from the injectors flows through the fuel pressure regulator before returning through the fuel heater to the tank.
If equipped with the engine oil renewal system, engine oil flows from the engine block to the engine oil renewal system manifold. A small amount of oil flows from the engine oil renewal system manifold into the return side of the fuel pressure regulator. The engine oil returns to the fuel tank with the return fuel.
The engine oil mixes with the fuel in the tank and flows with the fuel to the injectors to be burned. Fuel Tank Fuel Transfer Pump Primary Fuel Filter Secondary Fuel Filters Cylinder Head Cylinder Head Fuel Pressure Regulator Engine Ecm Fuel Priming Pump Fuel Heater Engine Block Engine Oil Renewal Solenoid
Air Induction and Exhaust System
The engine receives clean air through the air filters located on the front of the truck (789C) or on either side of the engine (785C). Any restriction caused by plugged filters can be checked at the filter restriction indicators (1). If the yellow piston is in the red zone, the filters must be cleaned or replaced.
Check the dust valves (2) for plugging. If necessary, disconnect the clamp and open the cover for additional cleaning. The dust valve is OPEN when the engine is OFF and closes when the engine is running. The dust valve must be flexible and close when the engine is running or the precleaner will not function properly and the air filters will have a shortened life. Replace the rubber dust valve if it becomes hard and not flexible.
The VIMS will also provide the operator with an air filter restriction warning when the filter restriction is approximately 6.2 kPa (25 in. of water). Black exhaust smoke is also an indication of air filter restriction.
Two filter elements are installed in the filter housings. The large element is the primary element and the small element is the secondary element.
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The turbocharger inlet pressure sensor (1) is located in a tube between the air filters and the turbochargers. The Engine ECM uses the turbocharger inlet pressure sensor in combination with the atmospheric pressure sensor to determine air filter restriction. The ECM provides the input signal to the VIMS, which informs the operator of the air filter restriction.
If air filter restriction exceeds 6.25 kPa (25 in. of water), an air filter restriction event will be logged, and the ECM will derate the fuel delivery (maximum derating of 20%) to prevent excessive exhaust temperatures. A factory password is required to clear this event. If the Engine ECM detects a turbocharger inlet pressure sensor fault, the ECM will derate the engine to the maximum rate of 20%. If the Engine ECM detects a turbocharger inlet and atmospheric pressure sensor fault at the same time, the ECM will derate the engine to the maximum rate of 40%.
The Engine ECM will automatically inject ether from the ether cylinders (2) during cranking. The duration of automatic ether injection depends on the jacket water coolant temperature. The duration will vary from 10 to 130 seconds. The operator can also inject ether manually with the ether switch in the cab on the center console (see Visual No. 48). The manual ether injection duration is 5 seconds. Ether will be injected only if the engine coolant temperature is below 10° C (50° F) and engine speed is below 1900 rpm.
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Shown is the 3516B engine used in the 789C truck. The 3516B engine is equipped with four turbochargers (arrows). The 785C truck has a 3512B engine with two turbochargers.
The turbochargers are driven by the exhaust gas from the cylinders which enters the turbine side of the turbochargers. The exhaust gas flows through the turbochargers, the exhaust piping, and the mufflers.
The clean air from the filters enters the compressor side of the turbochargers. The compressed air from the turbochargers flows to the aftercoolers. After the air is cooled by the aftercoolers, the air flows to the cylinders and combines with the fuel for combustion.
An exhaust temperature sensor (arrow) is located in each exhaust manifold before the
turbochargers. The two exhaust temperature sensors provide input signals to the Engine ECM. The ECM provides the input signal to the VIMS, which informs the operator of the exhaust temperature.
Some causes of high exhaust temperature may be faulty injectors, plugged air filters, or a restriction in the turbochargers or the muffler.
If the exhaust temperature is above 750° C (1382° F), the Engine ECM will derate the fuel delivery to prevent excessive exhaust temperatures. The ECM will derate the engine by 2% for each 30 second interval that the exhaust temperature is above 750° C (1382° F) (maximum derate of 20%). The ECM will also log an event that requires a factory password to clear.
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This schematic shows the flow through the air induction and exhaust system.
The turbochargers are driven by the exhaust gas from the cylinders which enters the turbine side of the turbochargers. The exhaust gas flows through the turbochargers, the exhaust piping, and the mufflers.
The clean air from the filters enters the compressor side of the turbochargers. The compressed air from the turbochargers flows to the aftercoolers. After the air is cooled by the aftercoolers, the air flows to the cylinders and combines with the fuel for combustion.
Muffler From Air Filters Aftercooler 3512B AIR INDUCTION AND EXHAUST SYSTEM From Air Filters
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