SEAT-VALVE 8J2309 - Caterpillar

General Operation of the Fuel System
Illustration 1 g00468817
(1) Fuel tank (2) Fuel transfer pump (3) Manual fuel shutoff valve (4) Water separator (5) Primary fuel filter (6) Mechanical governed fuel injection pump (7) Fuel injection nozzles (8) Fuel return line from fuel injection nozzleWhen the engine is cranking, the fuel is pulled from fuel tank (1) by fuel transfer pump (2). The fuel transfer pump forces the fuel through the water separator (4) and the primary fuel filter (5) to the fuel injection pump (6) . When the fuel goes through the water separator, any water in the fuel will go to the bottom of the bowl. The water can be drained through a valve which is located at the bottom of the bowl. If the engine does not have water separator (4), primary fuel filter (5) functions as a water separator. The primary fuel filter can be drained through a valve that is located at the bottom of the filter housing.A manually operated fuel shutoff valve (3) is located between the fuel transfer pump and the fuel filter. The fuel can be turned off by this valve in order to change the fuel filters. The fuel should be turned off for most repairs and maintenance of the engine.The fuel flows from the water separator at low pressure to primary fuel filter (5). The fuel flows at low pressure from the fuel filter to fuel injection pump (6) .The fuel injection pump sends fuel at high pressure to each fuel injection nozzle (7). The fuel injection nozzle sprays fuel into a precombustion chamber which slows the rate of combustion in the cylinder. The following items will result from reducing the rate of fuel combustion: prevention of engine knock, reduction of noise and reduction of emissions.
Illustration 2 g00468241
Phases of operation of the fuel injection nozzle (A) Closed valve (B) Open valve (C) Fully open valveThe fuel injection nozzle injects fuel into the precombustion chamber at different angles during two phases. Most of the fuel is injected when the valve is fully open (C). This process is called indirect fuel injection. The results are more even combustion and complete combustion of the fuel at a reduced temperature. Improved fuel combustion will increase power output while reducing emissions and reducing fuel consumption.Excess fuel from the fuel injection nozzles flows through fuel return line (8) to the inlet side of primary fuel filter (5). The excess fuel aids the cooling of the fuel injection nozzles. Also, the fuel return line removes any air that is trapped in the fuel injection nozzles and the fuel injection pump.The fuel injection pump needs fuel for lubrication. If the precision parts of the pump are not adequately lubricated, the components may be easily damaged. The engine must not be started until the fuel injection pump is full of fuel that is free of air.The system must be primed when any part of the system is drained of fuel. The following list contains examples of both service and repairs