Low Pressure Pump
DESCRIPTIONThe electric fuel pump is located in the fuel tank The pump draws warm or hot fuel from the fuel tank module bowl and also draws cool fuel out of the tank The cool fuel is drawn in and is mixed with the fuel already in the bowl in a 50-50 mix ratio Refer to fuel pump module for servicing (Refer to FUEL SYSTEM/FUEL DELIVERY/FUEL TANK MODULE - REMOVAL).
OPERATION
LOW PRESSURE SIDE
Low Pressure Side:
The fuel supplied by the low pressure pump flows through the fuel supply (5) at the high pressure pump and is passed to the flow control valve (11) and the fuel pressure relief valve (9). Any air entrained by the fuel is directed through the restrictor (10) through the bleed port (7) to the return flow (6). The quantity control valve (11) controls the amount of fuel that flows along the ring passage (4) through the supply ports to the three high pressure pump elements. To lubricate the plunger and barrel assemblies when the quantity control valve is closed (over run mode), the fuel is led directly to the circular port by the zero delivery restrictor (10).
The fuel pressure relief valve (9) limits the fuel pressure which exists at the fuel quantity control valve (11) to approximately 5 bar (72.5 psi). If the pressure is exceeded, the pressure relief valve opens and passes the fuel to the return flow (6).
The fuel pressure relief valve (9) directs a portion of the fuel as a lubricant to the eccentric shaft (8).
LOW PRESSURE PUMP
When the ignition switch is on, fused battery positive voltage is supplied to the electric lift pump, which will run for 20-30 seconds and then stop. If the engine is cranked, the pump will begin running immediately supplying fuel through fuel filter and onto the high pressure pump. The lift pump and low pressure fuel circuit operate at a pressure between 5-7 bar (72.5-101 psi.).