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| Illustration 1 | g06236287 |
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Fuel system diagram (1) High-pressure supply line (2) Fuel injector (3) Rail Pressure Sensor (RPS) (4) Fuel rail (5) Pressure relief valve for the fuel rail (6) Pressure regulator for the drain line (7) Fuel tank (8) Check valve for the fuel return (9) Diverter Valve (10) Electric priming pump (11) Fuel to the ARD (If equipped) (12) Primary fuel filter/water separator (13) Engine control module (ECM) (14) Fuel pressure sensor (secondary filter outlet) (15) Secondary fuel filter base (16) Fuel pressure sensor (secondary filter inlet) (17) Speed/timing sensor (18) Fuel Transfer pump (19) High-pressure fuel pump | |
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) (13).
This fuel system consists of five major components:
- High-pressure fuel pump (19)
- Engine Control Module (ECM) (13)
- Fuel Injectors (2)
- Fuel rail (4)
- Fuel transfer pump (18)
Note: The components of the fuel system are not serviceable. These fuel system components cannot be disassembled. Disassembly will damage the components. If the components have been disassembled, Caterpillar may not allow a warranty claim or Caterpillar may reduce the warranty claim.
The transfer pump (18) pulls fuel from the fuel tank (7) through the 10 micron primary fuel filter (12). 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 (16) measures the fuel pressure at the inlet of the secondary fuel filter. Fuel pressure sensor (14) 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 (4). The fuel rail (4) distributes the fuel to the fuel injectors (2) by the use of fuel lines. The fuel rail uses a fuel pressure sensor (3) that tells the ECM (13) about the pressure of the fuel rail. The ECM receives engine speed from the speed/timing sensor (17). The ECM controls the solenoids for the high-pressure fuel pump to obtain the correct amount of pressure. If pressure at the fuel rail is too high, the pressure relief valve (5) 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 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 (8) and pressure regulator (6).
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| Illustration 2 | g06236291 |
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A6:E2 ECM | |
Engine Control Module (ECM) is 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 to adjust the fuel delivery, injection pressure, and injection timing. The ECM contains programmed performance maps (software) 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 Cat® 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.
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| Illustration 3 | g06236499 |
| (1) Electronic Fuel Priming Pump | |
The electric priming pump (1) 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 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.
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| Illustration 4 | g06236645 |
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(1) High-pressure fuel pump
(2) Fuel transfer pump (3) Low-pressure fuel outlet (4) Low-pressure fuel inlet | |
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.
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| Illustration 5 | g06236655 |
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(5) Discharge ports to common rail
(6) Fuel return to tank (7) Fuel from fuel filter (8) Fuel metering valve (9) Engine oil inlet | |
The high-pressure fuel pump is an oil lubricated 2-cylinder in-line plunger high-pressure pump. It generates the pressure required by the Common Rail Injection System for all operating conditions of the engine. The fuel is pumped from the tank by the fuel transfer pump which is integrated on the high-pressure pump. The fuel delivery quantity can be controlled by the fuel metering unit (8). The system pressure can be governed continuously by the pump working at maximum, partial, and zero delivery.
Fuel Injector and High-Pressure Rail
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| Illustration 6 | g06236739 |
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(1) Fuel injector
(2) High-pressure fuel rail (3) High-pressure relief valve (4) Fuel rail pressure sensor | |
The common rail fuel system utilizes electronic controlled fuel injectors. Fuel injection occurs when the injector solenoid is energized by the Electronic Control Module (ECM). As the solenoid is energized, a magnetic force is generated. The magnetic force opens an internal fuel check valve. Fuel injection begins as the fuel pressure overcomes the pressure that is exerted by the spring force of the check valve.
A rail pressure sensor is installed in the high-pressure fuel rail. The rail pressure sensor monitors the fuel pressure that is inside 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 always.
The leakoff fuel from each injector passes into a pipe that is connected to each injector. The pipe is connected to the pressure relief valve and the fuel injection pump to return the leakoff fuel to the fuel tank.