PIN ASSEM. 5C8172 - Caterpillar

Fuel Flow
Illustration 1 g01246314
Fuel system schematic (1) Secondary fuel filter base (2) Fuel injection pump housing (3) Pressure regulating valve (4) Fuel injection line (5) Fuel injection nozzle (6) Fuel return line (7) Electronic control module (ECM) (8) Fuel transfer pump (9) Fuel priming pump (10) Primary fuel filter (11) Fuel tankFuel transfer pump (8) pulls fuel from fuel tank (11) through the primary fuel filter (10) .Note: When the engine has reached the normal operating temperature, the inlet fuel temperature to the transfer pump must not exceed 65°C (149°F). Fuel temperatures that are above 65°C (149°F) will reduce the life of the electronics within the ECM. High fuel temperatures will also reduce the life of the transfer pump check valves. Also, high fuel temperatures will reduce engine power output. If the engine is equipped with auxiliary fuel heaters, make sure that the fuel heaters are turned OFF in warm weather operating conditions.From the fuel transfer pump, (8) the fuel is pushed through the ECM (7). This will keep the electric circuits cool. The cooling plate for the control module is a one piece die cast aluminum housing. The manifolds on the top and the bottom of the control module route fuel from the transfer pump through the cooling plate.The fuel flows from the ECM through the secondary fuel filter. The fuel flows from the secondary fuel filter to the fuel manifolds in the fuel injection pump housing (2) .The fuel manifolds supply fuel for each fuel injection pump. A pressure regulating valve allows a constant fuel flow through the fuel return line (6) and back to fuel tank (11). The pressure regulating valve controls the pressure in the manifolds. Also, the pressure regulating valve controls the amount of fuel that goes back to the fuel tank (11). The constant flow of fuel back to the tank removes air from the system.Individual fuel injection lines carry fuel from the fuel injection pumps to each cylinder. One section of line connects between the fuel injection pump and an adapter that is located on the valve cover base. Another section of line connects between the adapter and the fuel injection nozzle that is located inside the valve cover base.The fuel transfer pump (8) is installed on the opposite side of the rotary servo pump on the end of the fuel injection pump. The fuel transfer pump has a pressure relief valve. The fuel transfer pump also has a bypass valve. The pressure relief valve controls the maximum pressure of the fuel to the fuel injection pump housing. When the pressure gets too high, the relief valve opens. This directs the fuel back to the inlet side of the transfer pump. The bypass valve allows the fuel to go around the transfer pump gears when the fuel priming pump (9) is used.When there is air on the inlet side of the system, the fuel priming pump (9) is used before the engine is started. The fuel priming pump is used to fill