Isuzu 4HK-1, Руководство пользователя, Страница: 14 / 50

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Isuzu 4HK-1 and 6HK-1 Engine Fuel Schematic Overview
Fuel System Hydraulic Function
Fuel comes from the tank and typically will go through a prefilter assembly. From the
prefilter, the fuel then flows to an electric fuel pump, located in the hydraulic pump
compartment. The 24 volt electric fuel pump is powered directly by the battery relay,
through the 65 amp fuse (F23) and the 10 amp electrical fuel pump fuse (F8) in the fuse
box. The electric fuel pump then sends the fuel through the fuel filter also located
hydraulic pump compartment to the inlet port of the high pressure injection pump.
The high pressure injection pump is mounted at the left rear of the engine. This pump
needs to be timed to the engine. To install the pump, bring the engine to TDC and then
align the mark on the pump drive gear to the mark on the front face of the high pressure
pump. Once these conditions are met, install the injection pump. The high pressure
injection pump has a shaft driven gerotor feed (charge) pump which provides fuel to the
pump pressure control valve (Suction Control Valve SCV). The gerotor pump outlet
pressure is controlled by the regulation valve to provide a constant pressure at the inlet
of the high pressure pumping pistons. The high pressurepump PSI regulator (SCV),
located in the injection pump, controls the flow output of the high pressure pump. The
high pressure pump supplies the quantity of fuel to the common rail required to maintain
the pressure dictated by the engine control unit (ECM). This assures that only the
required amount of fuel is pressurized, improving energy efficiency and limiting heating
of fuel in the system. The common rail pressure will range from 3625 to 29,000 PSI (25
to 200 MPa). Excess flow from the feed pump and internal leakage from the injection
pump returns to the tank. The fuel temperature sensor (FT) monitors the temperature of
this fuel.