Fuel Pump Relay: Description and Operation

Fuse / Relay Locations:

The fuel pump relay, which is located on the fuse box (under left side of instrument panel), provides battery voltage to the fuel pumps and the oxygen sensor heater element.
When the ignition switch is turned "ON", battery power flows through the switch to terminal 86 of the fuel pump relay and to the CIS-E motronic control unit. Simultaneously, the CIS-E motronic control unit provides a ground signal for approx. 1 - 2 seconds at terminal 85, energizing the fuel pump relay and pressurizing the fuel system. The CIS-E motronic unit will continue to provide a ground at terminal 85 of the fuel pump relay if it receives a signal of approx. 225 RPM of more (cranking or running). If the RPM signal is not present, the fuel pump relay will not operate preventing possible flooding or fire danger due to an accident.