Ok heres the deal Engine runs ok. but when I turn on the key, the fuel pump does not prime. When I crank the engine fuel pump operates as normal and starts after about 30 seconds the fuel pump relay appears to be fine but no voltage on the wire coming from the main relay to fuel pump relay. I beleave this is were the prime signal comes from. Ok ready to stand corrected....

Doug

 

Help us help you....... Year and model???

 

oopps sorry 85 xj6 series 3

 

Your model doesn't have a "prime" capability.

The fuel pump relay is triggered by voltage from:

A) the starter circuit to power the pump when cranking, as you've observed

B) a switch inside the air flow meter to power the pump when the engine is running

Voltage from either of these sources goes thru the red diode pack and triggers the fuel pump relay

The entire pump control circuit can be bypassed for diagnosed by removing the pump relay and applying 12v to the terminals in the socket that go to the white/green wires. You should hear the pump run. If the car starts and runs properly then you know you have a problem in the circuit. If the problem doesn't change, look elsewhere.

Do you have a fuel pressure gauge by the way? You might need one.


This might help for fuel pump circuit testing:

Fuel Pump Circuit Checklist

Since the car basically runs well I think you may have a problem not related to the fuel pump. Does the problem occur hot, cold, randomly, always?

Cheers
DD

 

Once again, Doug is quicker on the draw! He's got you covered.

Cheers,