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 in the fuel pump controls maximum fuel pump pressure.
On CPI fuel systems, pressure regulator is mounted to fuel metering body inside intake manifold. On TBI fuel systems, pressure regulator is mounted on throttle body.
When ignition switch is turned to ON position, control module turns on electric fuel pump by energizing fuel pump relay. Control module keeps pump on if engine is running or cranking (control module is receiving reference pulses from ignition module). If there are no reference pulses, control module turns pump off within 2 seconds after ignition is turned on.
Most models also include a second control path through the oil pressure switch which will turn the fuel pump on after the switch detects oil pressure. Cranking time will be longer if fuel pump does not receive current until oil pressure switch contacts close.