911 Carrera 4 Cabriolet AWD F6-3600cc 3.6L SOHC (1990)
Fuel Pump Relay: Description and Operation
The DME or fuel pump relay receives battery power to energize from the ignition switch and is grounded by the DME control unit. The switched
battery power that flows through the relay comes from the battery source terminal of the fuse box. The switched battery power flows through the relay
to the fuel pump as well as the oxygen sensor heating element. When the ignition is turned ON the fuel pump relay is energized for only 1 or 2 seconds
then the DME control unit shuts off the relay by removing the ground and de-energizing the relay. When the ignition switch is turned to the START
position the fuel pump relay again comes on for 1 or 2 seconds only. The fuel pump relay is kept energized after the DME control unit receives an rpm
signal from the ignition system, this rpm signal confirms that the engine is running above 225 rpm. The purpose of this feature is to prevent flooding
while starting, and to stop the fuel pump in the event of an accident and fire.
