SEAL-RING 1237269 - Caterpillar

Illustration 1 g01061346
Fuel system schematic
(1) Fuel supply line
(2) Electronic unit injectors
(3) Fuel gallery
(4) Electronic Control Module (ECM)
(5) Fuel pressure sensor
(6) Fuel temperature sensor
(7) Pressure regulating valve
(8) Secondary fuel filter
(9) Fuel priming pump
(10) Fuel transfer pump
(11) Primary fuel filter
(12) Fuel tank The fuel supply circuit is a conventional design for engines with electronic unit injection. A fuel tank (12) is used to store the fuel prior to use by the engine. A primary fuel filter/water separator (11) is placed into the fuel supply circuit in order to remove large debris from the fuel. This debris may have entered the fuel tank during fueling. The debris may have also entered the fuel tank through the vent for the fuel tank. 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.Fuel is drawn from the fuel tank by the fuel transfer pump (10). The fuel transfer pump is a gear pump with fixed clearances. The fuel transfer pump incorporates an internal relief valve that protects the fuel system from extreme pressure. In the case of extreme pressure, fuel is redirected back to the inlet of the fuel transfer pump. There are internal check valves that are also incorporated into the fuel transfer pump. An inlet check valve prevents fuel from draining back to the fuel tank while the fuel transfer pump is not in operation. An outlet check valve is used in order to prevent pressurized fuel leakage back through the pump. The fuel transfer pump is located in the front of the engine. The fuel transfer pump is driven by the front gear train.Note: The inlet fuel temperature to the fuel transfer pump must not exceed 79 °C (175 °F) when the engine has reached normal operating temperature. Fuel temperatures above 79 °C (175 °F) will reduce the life of the fuel transfer pump check valves. The fuel efficiency and the engine power output are reduced when the fuel temperature increases from 30 °C (86 °F) to 70 °C (158 °F). The fuel heaters should be turned "OFF" during warm weather operating conditions.Fuel from the fuel transfer pump flows to the fuel filter base. The fuel flows through cored passages in the fuel filter base. The fuel priming pump (9) is mounted on the fuel filter base. The fuel priming pump is used in order to pump the fuel manually into the fuel system after the system, or parts of the system have been drained. The fuel priming pump is used in order to refill the fuel system after air has been introduced into the system. For more information on priming the fuel system, refer to Testing and Adjusting, "Fuel System - Prime".As the fuel flows through cored passages in the fuel filter base, the fuel is directed into a 2 micron fuel filter (8). The fuel is filtered in order to remove small abrasive particles that will cause premature wear to fuel system components.