CORE ASSEM. 1W8440 - Caterpillar

Introduction
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 sensorThe 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, Caterpillar may not allow a warranty claim or Caterpillar 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, Caterpillar may not allow a warranty claim or Caterpillar 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