i have 1988 ford f-150 that ran great shut off the motor and would not restart 10 min later.i have replaced both fuel pumps,filter and relays still nothing.i checked for 12 volts in harness going to pumps and nothing,no power any suggestions,please help.

i have 1988 ford f-150 that ran great shut off the motor and would not restart 10 min later.i have replaced both fuel pumps,filter and relays still nothing.i checked for 12 volts in harness going to pumps and nothing,no power any suggestions,please help.
I have same problem, sometimes rotted wires at fuel pump, check wires

The fuel pump relay is ECM activated, the ECM grounds the relay coil energizing it.

Jump the power and pump feed terminals and see if the pumps work. If not, and you have poewr TO the relay for sure, then you definately have a wiring issue. The first place to look is at the main connector under the master cylinder (wires lead down to the frame). That is a very common place for a bad connection. The next likely place is just ahaed of the frame mounted pump at the large connector inside the frame.

Do not overlook the possibility that the problem is AT the relay (broken or corroded wire or terminal).

i have 1988 ford f-150 that ran great shut off the motor and would not restart 10 min later.i have replaced both fuel pumps,filter and relays still nothing.i checked for 12 volts in harness going to pumps and nothing,no power any suggestions,please help.
If you have power going to and leaving the fuel pump relay, check the inertia switch. (fuel pump saftey shut off switch) It should be located behind the right kick panel, in the passenger compartment. The contacts in these can become oxidized and loose connection. Press the button on top of it , to see if it needs to be reset. If not, hook a test light to the wires. Grn/y is the feed, and red/y goes to the pumps i think. Key on, you should have power for a few seconds, then the ecm shuts it back off if the engine doesnt start. If you have power going to , but not leaving this switch, put a jumper wire on the harness and see if it starts. If it does , replace the switch. Dont be tempted to run it with the jumper in place for long. Its there to shut the pumps off in case of an accident, and cut down on the risk of fire. good luck
Later
Ed
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I believe there is a fuse near your battery, 30 amp from your starter solenoid which is for your fuel?

Ed, you seem to know your stuff. I just did another posting, but I am desperate. Please read my other posting about dual tanks, and see if you have any ideas. THANKS!!

Ed, you seem to know your stuff. I just did another posting, but I am desperate. Please read my other posting about dual tanks, and see if you have any ideas. THANKS!!
If you havent already, check all your fuses, there are several related to this. Make sure you have the correct relay, parts stores make mistakes sometimes, and a relay may plug in but not be the right one. Compare the pinout with the old relay. Check to see if the relay socket is being energized when you turn the key on. Hook a test light to the red, of the two smaller wires, it should come on for a few seconds then go off. If it doesnt , check the pcm/eec relay, and related fuses, it powers the fuel pump relay. Try this and let us know.Good luck
Later
Ed

Ed,
Thanks for the quick reply. I did also check all of the fuses under the dash. I checked power, and I have 12v on one of the large wires all of the time, and power to one of the small leads when the key is on. The relay has the same pin configuration as the old one. I can make the truck run if I jumper the two large wires together. This is extremenly puzzling. Any other ideas are greatly appreciated!!

Ed,
Thanks for the quick reply. I did also check all of the fuses under the dash. I checked power, and I have 12v on one of the large wires all of the time, and power to one of the small leads when the key is on. The relay has the same pin configuration as the old one. I can make the truck run if I jumper the two large wires together. This is extremenly puzzling. Any other ideas are greatly appreciated!!
Ok, if you have power on the large(yel) wire all the time, and on the small(red) key on, that rules out a fuse problem. Just for grins, check the relay to make sure its good. Swap it with another, like the horn relay, or hook 12v to it and check it with a meter or test light. Your possibilities are getting slimmer, the other small wire in the relay socket is the signal ground from the pcm/eec. It comes from pin 22 of the computer/eec. The computer recieves inputs from several other pins, and controls the ground to the socket that energizes the holding coil of the relay. I think now the problem either has to be the wire from the socket to pin 22, or the eec itself. A scan may show the problem to be in the eec., and you can check the continuity of the wire if you have an ohmmeter. Or you might pick one up at a junk yard and try it. You can make up some jumper wires to hook up the relay out of the socket, just hook the other small wire(tan/lt grn) from that pin of the relay directly to ground. It should then work with the key, and you wont have to keep unhooking the jumper. Use insulated spade connectors to make sure nothing can short out. Let us know. Good luck.
Later
Ed
PS: check your grounds from batt. to body, frame, harnesses, and the socket itself for dirt corrosion.

Ed, You really know your stuff!! I am anxious to get home from work and try your ideas!! I sent you my email for the diagrams, but your excellent descriptions may be all I need!! Thanks again, and I will certainly keep posting my findings in the hope that if someone else has this problem, it will help them out!!! THANKS AGAIN!!

:grinyes: IT LIVES!! I installed the new relay from Advance, and it apparently was bad, The truck would run, but when you shut it off, the fuel pump kept running. I reinstalled the old relay, and all works well. I am fairly sure it was the two small ground wires as someone else mentioned, on the negative cable by the battery. They were severely corroded and basically broken through. I replaced both battery cable ends, and put the two small grounds on a seperate lug, bolted directly on my replacement cable ends. Thanks to all, especially Ed, for the help!! It was greatly appreciated!!!!!

Well, that was short lived. It is doing the same thing again. Now it is stranded in a parking lot, but I will play with it in the daylight!!
IT IS FIXED AGAIN!! A new relay from FORD did the trick!! IT was $40, not the $15 from Advance, but that fixed it for sure!!!!! I am posting this just in case someone else has the same issues!!