ENGINE 129 B. FUEL FILTER The Fuel filter is fitted as a second filtering step in the fuel feed system. It is mainly used to filter out particles that are present in the fuel. For removal and refitment refer Engine on vehicle repairs in this section. ! CAUTION The fuel filter and fuel sedimentor should be replaced as recommended in the service schedule. If this is not done, it may result in impurities or particles entering the High pressure system causing damage to the Fuel Injection components. C. PRIMING PUMP Priming pump is provided in the low pressure line just before the fuel filter. It is used to prime the fuel feed system with fuel. This is done in order to avoid air lock in the system. The advantage is that the fuel lines need not be loosened or dis-connected to bleed the system. Priming can be done by pressing and releasing the bulge repeatedly till it is filled with fuel. Fuel System Priming Procedure: If the performance of the engine is affected due to the presence of the air in fuel system (commonly known as air lock), then detect can be removed by bleeding the fuel system. This can be done by pumping the priming pump (Fig. 17) by hand. Start engine and check for fuel leakage. Rectify if necessary. Check for smooth running of engine. Whenever replacing fuel sedimentor or filter, use priming pump to complete the fuel flow circuit. NOTE Do not loosen the HP lines for bleeding the air from fuel system. Bleeding of the fuel system should be done only using priming pump. D. COMMON RAIL It is a fuel reservoir where the fuel is maintained at a pressure of about 1600 bar. The fuel is pumped into it from the HP pump and gets delivered to the injectors through the HP lines. It is also fitted with a rail pressure (RP) sensor and the signal is used by EMS ECU to maintain the fuel pressure. NOTE Whenever fuel rail is removed from the engine, always cover the inlet and outlet openings of the rail with the protective caps.
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