PLATE 4V0612 - Caterpillar

Introduction
Illustration 1 g03597997
Typical example (1) Fuel strainer (2) Primary fuel filter (3) Electric transfer pump (4) Secondary fuel filter (5) Fuel Injection Pump (6) Inlet pressure regulator (7) Fuel manifold (rail) (8) Pressure relief valve (9) Electronic unit injector (10) Fuel cooler (if equipped) (A) Fuel tankFuel is drawn from the fuel tank through a fuel strainer to an external electric transfer pump. The fuel then flows to the 10 micron primary fuel filter and a water separator.The fuel then flows to a 4 micron secondary fuel filter.The fuel flows from the secondary fuel filter to a pressure regulator. A pressure regulator that is installed in the low-pressure fuel system controls the fuel pressure to the fuel injection pump.From the pressure regulator, the fuel flows to the fuel injection pump. The fuel is pumped at an increased pressure of up to 200 MPa (29000 psi) to the fuel manifold (rail).High Pressure Fuel System
Illustration 2 g03591150
Typical example (1) Fuel injection pump (2) Fuel temperature sensor (3) Suction control valve for the fuel injection pump (4) Fuel pressure sensor (5) Electronic unit injector (6) Fuel manifold (rail) (7) Pressure relief valve (8) Fuel transfer pumpThe fuel injection pump (1) feeds fuel to the high-pressure fuel manifold (rail) (6). The fuel is at a pressure of up to 200 MPa (29000 psi). A pressure sensor (4) in the high-pressure fuel manifold (rail) (6) monitors the fuel pressure in the high-pressure fuel manifold (rail) (6). The ECM controls a suction control valve (3) in the fuel injection pump (1) in order to maintain the actual pressure in the high-pressure fuel manifold (6) at the desired level. The high-pressure fuel is continuously available at each injector. The ECM determines the correct time for activation of the correct electronic unit injector (5) which allows fuel to be injected into the cylinder. The leakoff fuel from each injector passes into a drilling which runs along the inside of the cylinder head. A pipe is connected to the rear of the cylinder head in order to return the leakoff fuel to the fuel tank.Components of the Fuel Injection System
The fuel injection system has the following mechanical components:
Primary filter/water separator
Electric transfer pump
Fuel transfer pump
Secondary fuel filter
Fuel injection pump
Fuel injectors
Fuel manifold
Pressure relief valve
Fuel pressure sensor
Fuel temperature sensorThe following list contains examples of both service and repairs when you must prime the system:
A fuel filter is changed.
A low-pressure fuel line is replaced.
The fuel injection pump is replaced.
The ECM is replaced.For the correct procedure to prime the fuel system, refer to Systems Operation, Testing and Adjusting, "Fuel System - Prime".Primary Filter/Water Separator
Illustration 3 g03598437
Typical exampleThe primary filter/water separator (1) is located between the electric lift pump and the secondary fuel filter. The primary filter/water separator (1) provides a 10 micron filtration level.Secondary Fuel Filter
Illustration 4 g03598036
Typical exampleThe secondary fuel filter (1) is located after the primary fuel filter. The secondary fuel filter (1) provides a 4 micron filtration level.Fuel Pump Assembly
Illustration 5 g02450146
Typical exampleThe fuel pump assembly consists of a low-pressure transfer pump and a