Fuel Pump
WARNING: This page does not describe the selected car, but rather 15 other vehicles, including the 2003 Hummer H2, 2003 GMC Yukon XL, 2003 GMC Yukon, 2003 GMC Sierra, and 2003 GMC Savana. However, it is still accessible from the selected car via links, so may be relevant.
An in-tank, electric fuel pump delivers fuel to injector(s) through an in-line fuel filter. The pump is designed to supply fuel pressure in excess of vehicle requirements. The pressure relief valve controls maximum fuel pump pressure. Pressure regulator keeps fuel available to injector(s) at a constant pressure. Excess fuel is returned to fuel tank through pressure regulator return line.
When ignition switch is turned to ON position, PCM turns on electric fuel pump by energizing fuel pump relay. PCM keeps pump on if engine is running or cranking (PCM is receiving reference pulses from ignition module). If there are no reference pulses, PCM turns pump off.