Fuel Pump On/Off Control

PURPOSE
The Fuel Pump Control System allows the Engine Control Module
(ECM) to control the shared power circuit of the Fuel Pump and the Air Regulator via the fuel pump relay. The ECM can prevent the fuel pump from operating with the ignition key "on" and the engine "off". This feature improves safety and prevents unnecessary battery discharge.

OPERATION
The ECM supplies the ground circuit for the fuel pump relay for a few seconds after the ignition switch is turned on. The grounded fuel pump relay will then power the Fuel Pump. If the ECM receives a 1° signal from the crankshaft position sensor, indicating the engine is on or starting, it continuously supplies the circuit.

The ECM will power the Fuel Pump / Air Regulator circuit:

- for 1.5 seconds after the ignition switch is "on"
- while the engine is cranking and/or running
- for 1.5 seconds after the engine stops

If the 1° signal is not present, indicating a stalled engine, the ECM opens the ground circuit which stops the fuel pump.