BOLT 7X2561 - Caterpillar

Illustration 1 g00322667
Fuel Flow Schematic (Typical Example) (1) Fuel manifolds. (2) Fuel filter. (3) Fuel priming pump. (4) Fuel injectors. (5) Pressure regulating valve. (6) Fuel return to tank. (7) Primary fuel filter. (8) Fuel transfer pump. (9) Fuel line to filter. (10) Fuel supply line from the primary fuel filter. (11) Fuel line to priming pump.Fuel transfer pump (8) is located on the right side of the engine. The lower shaft of the engine oil pump drives the gear type transfer pump. Fuel from the supply tank is pulled through primary fuel filter (7) by fuel transfer pump (8) and sent to fuel filter (2) .Fuel transfer pump (8) has a check valve and a bypass valve. The check valve is located in the pump head assembly. The pump head assembly is located behind the connection for line (9). The check valve prevents fuel flow back through the transfer pump when fuel priming pump (3) is used. The bypass valve is located behind a cap (plug) in the drive end of the pump. The bypass valve limits the maximum pressure of the fuel. The bypass valve will open the outlet side of the pump to the pump inlet if the fuel pressure exceeds 860 kPa (125 psi). This process helps prevent damage to the fuel system components from too much pressure.
Illustration 2 g00316127
Right Front Of Engine (Typical Example) (1) Fuel manifolds. (2) Fuel filter. (8) Fuel transfer pump. (9) Fuel line to filter. (10) Fuel supply line from the primary fuel filter. (11) Fuel line to the priming pump.The transfer pump pushes fuel through the fuel filter (2) on the front of the engine to fuel manifolds (1). The fuel flows through the manifold to inlet fuel line (13) connected to the right side of each cylinder head. Filter screens are located in the ports of the unit injector. A drilled passage (14) in cylinder head (15) takes fuel to a circular chamber around the injector. The chamber is made by the O-rings on the outside diameter of fuel injector (4) and by the injector bore in the cylinder head.
Illustration 3 g00322726
Cylinder Heads (4) Injector. (12) Outlet fuel line. (13) Inlet fuel line.Only part of the fuel in the chamber is used for injection. Approximately three to five times the amount of fuel that is needed for normal combustion flows through the chamber. This fuel then flows to a drilled passage in the left side of the cylinder head. This passage is connected by outlet fuel line (12) to the bottom section of the fuel manifold. This constant flow of fuel around the injectors helps to cool the injectors.
Illustration 4 g00322727
Fuel Flow Through Injector (4) Fuel injector. (12) Outlet fuel line. (13) Inlet fuel line. (14) Drilled passage. (15) Cylinder head. (16) Cylinder.The fuel flows back through the fuel manifold. The fuel flows to pressure regulating valve (5) on the front of the right fuel manifold. The fuel flows through this valve. Fuel then flows back to the tank.Check each engine