Fuel Pump - Electrical

The early 911 CIS fuel pump wiring was simple. Turn on the ignition to the Run position and power is immediately supplied to the fuel pump. Not even a fuse got in the way.

Beginning with the '76 year model, that changed. A relay was placed in the circuit and the pump got a fuse. See the relay circuit below. For details on how this works, go to CIS Components • Component Descriptions and click on Fuel Pump Relay.

Current track 96 in yellow is the fuel pump. Note that power is fed to the WUR and the AAR when the fuel pump is powered. The safety switch on the airflow sensor housing is at current track 95.

Over-rev protection was added in '78 by the addition of a speed relay that cut off the fuel pump above a certain speed by a signal from the Speedometer.