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| Illustration 1 | g06333200 |
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Fuel system diagram (Single Wall) (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) Check valve for the fuel return (10) Fuel cooler (11) Fuel tank (12) Speed/timing sensor (13) High-pressure fuel pump (14) Transfer pump (15) Fuel pressure sensor (secondary filter inlet) (16) Secondary fuel filter base (17) Fuel pressure sensor (secondary filter outlet) (18) Selector valve (19) Electronic Control Module (ECM) (20) Primary fuel filter/water separator (21) Electric priming pump | |
The operation of this fuel system is different from any other type of fuel system that is actuated mechanically. The fuel system is completely free of adjustment. Adjustments to the components that are mechanical cannot be made. Changes in performance are made by installing different software on the Electronic Control Module (ECM) (19).
This fuel system consists of five major components:
- Fuel pump (13)
- Electronic Control Module (ECM) (19)
- Fuel Injectors (4)
- Fuel rail (6)
- Fuel transfer pump (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, Caterpillar may not allow a warranty claim or Caterpillar may reduce the warranty claim.
Fuel System Operation (Single Wall)
Fuel is pulled from the fuel tank (11) and through the primary fuel filter (20) by the use of the transfer pump (14). The primary fuel filter/water separator removes large debris from the fuel. The primary filter element also separates water from the fuel. The water is collected in the bowl at the bottom of the primary fuel filter/water separator. 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 fuel priming pump (21) forces the air that is in the fuel system out through the injector cooling circuit and back to the tank.
The fuel transfer pump is a fixed displacement gear pump that is driven by the high-pressure pump. The fuel transfer pump receives fuel from the primary fuel filter. The fuel transfer pump also supplies cooling flow to the injectors, and the high-pressure pump. The transfer pump (14) sends the fuel through the secondary fuel filter and up to the fuel pump (13). The secondary fuel filter is used to remove abrasive material and contamination as small as 2 microns that could damage the injectors. The selector valve (18) is used to change the fuel flow to the optional fuel filter available on both primary and secondary filters in case of either of the one filter is clogged or blocked. The fuel pump (13) 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 quill tubes . The fuel rail uses a fuel pressure sensor (5) that tells the ECM (19) the pressure of the fuel rail. The ECM also receives engine speed from the speed/timing sensor (12). The ECM controls the solenoids for the fuel pump (1) to obtain the correct amount of pressure. If pressure at the fuel rail is too high, the pressure relief valve (8) will drain proper amounts of fuel back to the fuel tank. Once the fuel reaches the fuel injectors, the fuel injectors open a control valve that is inside the injector by the use of a solenoid. The fuel injectors deliver the high-pressure fuel into the combustion chamber at precise amounts of quantity and time. A drain in the fuel injector sends fuel that was not used during the delivery to the return line. The pressure regulator (8) keeps a constant back pressure on the fuel injector.
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| Illustration 2 | g06333194 |
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Fuel System Diagram (Dual Wall) (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) Leak detector manifold (8) Check valve (9) Fuel line (10) Pressure relief valve for the fuel rail (11) Pressure regulator for the drain line (12) Check valve for the fuel return (13) Fuel cooler (14) Fuel tank (15) Speed/timing sensor (16) High-pressure fuel pump (17) Transfer pump (18) Fuel pressure sensor (secondary filter inlet) (19) Secondary fuel filter base (20) Fuel pressure sensor (secondary filter outlet) (21) Selector valve (22) Electronic Control Module (ECM) (23) Primary fuel filter/Water separator (24) Electric priming pump | |
In dual wall rail fuel system, the dual wall rails are used to collect leaking high-pressure fuel. There is an additional fuel line (9) which is connected to a leak detector manifold (7).If an internal leak occurs, the check valve (8) will drain the fuel to the fuel tank. The Leak detector manifold consists of wet sensor which sends the signal to ECM (22). The check value is used to prevent the fuel in the return line entering the wet sensor manifold.
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| Illustration 3 | g01173131 |
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Side view (1) Solenoid (2) Control valve (3) Drain hole (4) Quill tube bore (5) Tip | |
The fuel system utilizes electronic controlled fuel injectors. This system uses electronically actuated solenoids (1) to control the injection of the fuel into the combustion chamber.
The injector uses a control valve (2) in order to control the delivery of fuel into the combustion chamber. The drain hole (3) sends unused pressurized fuel back to the secondary fuel filter. The other pressurized fuel is injected through orifice holes in the bottom of the tip (5). Fuel is inserted into the combustion chamber in precise amounts in order to control engine performance.
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.
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| Illustration 4 | g01173279 |
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Side view (6) Quill tube (7) Ball (8) O-ring seal (9) Nut | |
The quill tube (6) fits on the inside of the cylinder head. The quill tube is held in position by the use of a nut (9) and a ball (7). An O-ring seal (8) 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.
Electronic Control Module (ECM)
Electronic 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 in order to make adjustments to 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 Caterpillar Electronic Technician (ET).
ECM logs faults of engine performance. Also, the ECM is capable of running several diagnostic tests automatically when the ECM is used with an electronic service tool such as the Cat ET.
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| Illustration 5 | g01171732 |
| (10) Fuel pump | |
Fuel pump (10) is at the left front corner of the engine. The fuel pump uses electronic solenoids and RPM from the engine to pressurize the fuel.
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| Illustration 6 | g01171756 |
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(10) Fuel pump
(11) Fuel transfer pump | |
Fuel transfer pump (11) is mounted on the back of fuel pump (10). The fuel is pressurized to
The fuel transfer pump is a variable gear pump. The fuel transfer pump is driven by the shaft of the fuel pump. A relief valve in the fuel transfer pump limits the outlet pressure to
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| Illustration 7 | g01173232 |
| (12) Rail Pressure Sensor | |
Rail pressure sensor (12) 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.