RETAINER-SEAL 8R0933 - Caterpillar

Illustration 1 g00418398
Fuel System Schematic (1) Fuel filter base (2) Siphon break (3) Vent plug (4) Unit injectors (5) Fuel supply manifold (6) Drain plug (7) Fuel priming pump (8) Fuel return manifold (9) Secondary fuel filter (10) Fuel regulator valve (11) Fuel return port (12) Electronic control module (ECM) (13) Fuel transfer pump (14) Pressure regulating valve (15) Check valve (16) Fuel tankThe fuel supply circuit is a conventional design for unit injector diesel engines. Fuel transfer pump (13) is a gear type pump. The clearance in the fuel transfer pump is constant. The fuel transfer pump delivers fuel from the tank to unit injectors (4). Fuel is pulled from the fuel tank by the fuel transfer pump. The fuel transfer pump incorporates check valve (15) in order to allow fuel flow around the gears for hand priming. Pressure regulating valve (14) is used to protect the system from extreme pressure. The fuel transfer pump creates excess fuel flow that cools the unit injectors. The excess fuel flow also purges the air from the unit injectors. After the fuel transfer pump, the fuel flows through the cored passages in the electronic control module housing in order to cool the module. The fuel then flows through secondary fuel filter (9). Fuel priming pump (7) is located on the fuel filter base. The fuel priming pump is used to fill the system after draining the fuel supply and return manifolds. Fuel filter base (1) also incorporates siphon break (2) in order to prevent fuel from exiting the cylinder head during long periods of storage. Fuel priming pump (7) minimizes the fuel that returns to the tank by utilizing two check valves. The fuel flows continuously from the fuel supply manifold through the unit injectors and excess fuel is returned to the tank by fuel return manifold (8). The plunger displaces some fuel that is not injected into the cylinder. This fuel is also returned to the tank by the fuel return manifold. Refer to Systems Operation/Testing and Adjusting, "Unit Injector" for an explanation of the injection process.A flow control orifice is located in the fuel return manifold. The flow control orifice maintains sufficient system back pressure in order to fill the unit injectors. Superb fuel flow is provided to the unit injectors without excessive heating of the fuel tank. Fuel transfer pump (13) is located at the left front lower corner of the engine. The fuel transfer pump is driven by the lower accessory drive gear. The fuel supply and return manifolds are drilled passages in a common manifold which is mounted to the cylinder head. Fuel from fuel supply manifold (5) flows through drilled passages in the cylinder head, and into unit injectors (4). Fuel return port (11) is located at the end of fuel return manifold (8). The fuel return port is a part of fuel filter base (1). The pressure regulating orifice maintains the needed back pressure in order to fill the unit injectors. The pressure regulating