Introduction
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| Illustration 1 | g03711354 |
Fuel system diagram (1) Solenoid for the high-pressure fuel pump (2) High-pressure supply line (3) Cooling supply to injectors (4) Fuel injector (5) Rail Pressure Sensor (RPS) (6) Fuel rail (7) Pressure relief valve for the fuel rail (8) Pressure regulator for the drain line (9) Fuel tank (10) Check valve for the fuel return (11) Fuel to the Clean Emissions Module (CEM) (12) Electric priming pump (13) Primary fuel filter/water separator (14) Engine control module (ECM) (15) Fuel pressure sensor (secondary filter outlet) (16) Secondary fuel filter base (17) Fuel pressure sensor (secondary filter inlet) (18) Transfer pump (19) High-pressure high-pressure fuel pump (20) Speed/timing sensor | |
The operation of this fuel system is different from any other type of fuel system that is actuated mechanically. The fuel system is free of adjustment. Adjustments to the components that are mechanical cannot be made. Changes in performance are made by installing different software on the Engine Control Module (ECM) (14) .
Note: The components of the fuel system are not serviceable. These fuel system components must not be disassembled. Disassembly will damage the components. If the components have been disassembled, AVSpare may not allow a warranty claim or AVSpare may reduce the warranty claim.
This fuel system consists of five major components:
- High-pressure fuel pump (19)
- Engine Control Module (ECM) (14)
- Fuel Injectors (4)
- Fuel rail (6)
- Fuel transfer pump (18)
Note: The components of the fuel system are not serviceable. These fuel system components must not be disassembled. Disassembly will damage the components. If the components have been disassembled, AVSpare may not allow a warranty claim or AVSpare may reduce the warranty claim.
Fuel System Operation
The transfer pump (18) pulls fuel from the fuel tank (9) through the 10 micron primary fuel filter (13) . Transfer pump (18) sends the fuel through the 4 micron secondary fuel filter and the 4 micron tertiary fuel filter to high-pressure fuel pump (19) . Fuel pressure sensor (17) measures the fuel pressure at the inlet of the secondary fuel filter. Fuel pressure sensor (15) measures the fuel pressure that is entering the tertiary filter. The high-pressure fuel pump (19) pressurizes the fuel that is sent to the fuel rail (6) . The fuel rail (6) distributes the fuel to the fuel injectors (4) by the use of fuel lines. The fuel rail uses a fuel pressure sensor (5) that tells the ECM (14) about the pressure of the fuel rail. The ECM receives engine speed from the speed/timing sensor (20) . The ECM controls the solenoids for the high-pressure fuel pump (1) in order to obtain the correct amount of pressure. If pressure at the fuel rail is too high, the pressure relief valve (7) opens. This valve opening drains the excess fuel back to the fuel tank. The rail pressure can vary from 42 MPa to 190 MPa. Once the fuel reaches the injectors, ECM sends current to the injector solenoid in order to actuate the three-way valve inside the injector. As the valve opens, the fuel flows from the high-pressure line to the tip. As the valve opening pressure is reached, the check is lifted and fuel is delivered at high pressure into the combustion chamber. The fuel is then delivered in a precise quantity and at the right time. The injector bypasses the excess fuel to the tank through check valve (10) and pressure regulator (8) .
Component Description
Engine Control Module (ECM)
Engine Control Module (ECM) is located on the left side of the engine. The ECM is a powerful computer that provides total electronic control of engine performance. The ECM uses data from engine performance that is gathered by several sensors. Then, the ECM uses this data in order to adjust the fuel delivery, injection pressure, and injection timing. The ECM contains programmed performance maps (software) in order to define horsepower, torque curves, and rpm. This software is commonly called the personality module.
The engine does not have a replaceable personality module. The personality module is a permanent part of the ECM. The personality module for the engine can be reprogrammed by AVSpare Electronic Technician (ET).
ECM logs faults of engine performance. Also, the ECM can run several diagnostic tests automatically when the ECM is used with an electronic service tool such as the Cat ET.
Priming Pump
The electric priming pump forces the air that is in the fuel out of the system through the orifice on the regulator. Priming usually takes place after servicing the fuel system such as changing the fuel filter. This mode can also occur when the engine has not run for a long period. When the fuel system has air trapped in the fuel filters, lines, and other fuel system components, the engine could experience difficulty starting. The electric priming pump is turned on manually or the electric priming pump is turned on automatically in order to prime the system. The time for priming depends on the size of the fuel system. Nominal time of priming is about 30 seconds. This value varies by applications.
Fuel Transfer Pump
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| Illustration 2 | g01945334 |
(1) High-pressure fuel pump (2) Fuel transfer pump (3) Low-pressure fuel inlet (4) Low-pressure fuel outlet | |
Fuel transfer pump (2) is a pump that produces low pressure, high volume to pull fuel from the tank and through the primary fuel filter. Then, the pump sends the fuel through the secondary filter and the tertiary filter on the way to the high-pressure fuel pump. The high-pressure fuel pump feeds the injectors.
The transfer pump is mounted on the back of high-pressure fuel pump (1) . The fuel transfer pump is a variable gear pump, that is driven by the shaft of the high-pressure fuel pump. A relief valve in the fuel transfer pump limits the outlet pressure to 1009 kPa (146 psi).
High-pressure fuel pump
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| Illustration 3 | g01945336 |
(1) High-pressure fuel pump (5) Solenoids for the high-pressure fuel pump (6) High-pressure fuel outlet (7) Fuel return to tank (8) Fuel from fuel filter (9) Inlet for engine oil | |
High-pressure fuel pump (1) pressurizes the fuel to 190 MPa (27550 psi). The high-pressure fuel pump is located at the left front corner of the engine. The high-pressure fuel pump uses electronic solenoids and RPM from the engine to pressurize the fuel.
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| Illustration 4 | g01945338 |
Cross section of the high-pressure fuel pump (2) Fuel transfer pump (10) Electronic controlled metering valves (11) Camshaft roller tappet (12) Camshaft with three lobes | |
Quill Tube
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| Illustration 5 | g01945355 |
Side view (13) Quill tube (14) Ball (15) O-ring seal (16) Nut | |
The quill tube (13) fits on the inside of the cylinder head. The quill tube is held in position by the use of a nut (16) and a ball (14) . An O-ring seal (15) is used in order to help seal the quill tube in the head. Refer to Specifications, "Fuel Injector" for the proper installation of the quill tube.
Rail Pressure Sensor (RPS)
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| Illustration 6 | g01945356 |
(17) Rail Pressure Sensor | |
Rail pressure sensor (17) is installed in the high-pressure fuel rail. The rail pressure sensor monitors the fuel pressure that is inside of the fuel rail. The rail pressure sensor sends an analog voltage signal back to ECM. The ECM interprets the signal. The ECM is aware of the fuel pressure at all times.
Fuel Injector
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| Illustration 7 | g01945359 |
Side view (18) Solenoid (19) Control valve (20) Fuel supply (21) Holes for fuel cooling (22) Drain passage (23) Drain holes (24) Orifice plate (25) Nozzle spring (26) Check (27) Tip | |
The common rail fuel system utilizes electronic controlled fuel injectors. This system uses electronically actuated solenoids (18) to control the injection of the fuel into the combustion chamber. The injector uses a three-way control valve (19) to control the fuel delivery into the combustion chamber.
The pressurized fuel enters fuel supply (20) . Then, the pressurized fuel lifts the check against the valve inside the nozzle to allow the high-pressure fuel to be injected into the combustion chamber. There are orifices present in injector tip (27) that the fuel is injected through. The fuel is injected in precise amounts in order to control engine performance.
The injector is cooled by fuel which is routed through the engine cylinder head. The fuel enters the injector through holes for fuel cooling (21) . Cooling fuel exits the injector through the drain holes (23) .
There are many other operating conditions when the injection pressure is between the minimum and the maximum. Regardless of the speed of the engine, the fuel system provides complete control of injection pressure.