Wagoneer L6-242 4.0L VIN L FI (1989)
Fuel Pump Relay: Description and Operation
Relay Cluster Location -- On Right Front Wheel Well
This relay has voltage applied to it from the battery through the ignition switch. The ECU controls this relay by applying or taking away the ground from
its circuit. When the ground is applied, the relay is energized, and current is allowed to flow to the fuel pump through the fuel pump ballast resistor.
During start up battery voltage is supplied via the starter relay, whereas at wide open throttle battery voltage is supplied via oxygen sensor heater relay.
The ECU controls this relay for safety purposes also. In the event that the vehicle stalls, if no tach signal is sent to the ECU it will not apply the ground
to this relay, which will prevent voltage from getting to the fuel pump.
