SEAL 8D1791 - Caterpillar

Introduction
Illustration 1 g02450139
Typical example
(1) Fuel strainer
(2) Electric transfer pump
(3) Primary fuel filter
(4) ECM that is fuel cooled.
(5) Secondary fuel filter
(6) Fuel Injection Pump
(7) Inlet pressure regulator
(8) Fuel manifold (rail)
(9) Pressure relief valve
(10) Electronic unit injector
(11) Fuel cooler (optional)
(A) Fuel tank Fuel 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 may flow to a fuel cooled ECM. 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. The pressure regulator regulates the fuel at a pressure of 150 kPa (22 psi) when the engine is at idle speed.From the pressure regulator, the fuel flows to the fuel injection pump. The fuel is pumped at an increased pressure of 200 MPa (29000 psi) to the fuel manifold (rail).Fuel that has too high a pressure from the fuel manifold (rail) returns through the pressure relief valve to the return line. Fuel that is leak off from the electronic unit injectors flows to the return line. The fuel may then flow through an optional fuel cooler on the way back to the fuel tank.High Pressure Fuel System
Illustration 2 g02450116
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 pump The fuel injection pump (1) feeds fuel to the high-pressure fuel manifold (rail) (6). The fuel is at a pressure of 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 g02214535
Typical example
The primary