I have a 1994 F250 7.5L. When I turn the key to the on position some times the pump/s come on and some times not. When the pump does not come on I can tap on the PCM power relay and hear the pump come on. I swapped the relay with other relays from the same fuse box and also purchased a new one and still the same problem. I cleaned and inspected the terminals under the relays. Also un-plugged the fuel inertia switch and checked for voltage (with key on) and have 6V. While watching the meter I can tap on the PCM relay and see the voltage at the inertia switch plug jump up to 12V. for only a second and then goes back to 6V. When the pump does come on and the truck is running I can check voltage on the hot wire going into the inertia switch and it has 12 plus V. Also while truck is running I can lightly tap on PCM relay and the thruck will stall for a second and then pick back up. any ideas? all suggestions greatly appreciated.
Thanks for looking

 

Try changing the fuel pump relay then.



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I don't suppose you know where I can get pins to use that extra relay socket?