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Brian, Ford Shop Foreman
Category: Ford
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Experience:  Ford Senior Master certified Tech, 36 years Ford technician.
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1994 Ford f-150: wont start..Truck sat..radiator..the fuel pumps run

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1994 Ford f-150 wont start. Truck sat for about a month while I replaced the radiator. When I turn the key to the on position, I hear the fuel pumps run continuously and they won't shut off. I tried replacing the fuel filter and still no luck. Please help
The fuel pump relay may be stuck on due to not being started for a month. The relay is in the engine compartment fuse box, try unplugging the relay to see if the fuel pump shuts off.graphic
Customer: replied 8 years ago.
the fuel pump shuts off, but cuts right back on when I plug it back in. Truck still won't start

The relay is probably stuck, I would recommend to replace that first, I don't think it will cause it not to start, but lets get the fuel pump to shut off when it's supposed to.

Customer: replied 8 years ago.
I replaced the relay, when I turn the key to the on position the fuel pump will run then shut off. when it shuts off I hear a loud humming/surging noise coming from the new relay. The truck has duel tanks/pumps and both pumps are doing the same thing.
So now the pumps are turning off but the relay is humming or pulsing ?
Customer: replied 8 years ago.
yes they turn off, its more like a constant humming noise though from the relay
The computer controls the relay, it may have failed internally, I would try to disconnect the battery for a couple of minutes and reconnect it, if nothing changes, I would recommend to have it scanned for codes, see if any fault codes are present.
Customer: replied 8 years ago.
Hey bud i haven't forgot about you. Well I had my father-in-law investigate the humming relay noise, and he engaged the relay manually(stopped the humming) and the truck started. I guess that the duralast relay that I bought from autozone is crappy? I will try to get a better quality one and see how it works, so we can both move on.

Ok, let me know how it goes, great to work along with you, don't forget to click on the accept button,

Thanks, Brian.

Customer: replied 8 years ago.

The truck will only start/run when a relay is manually engaged/disengaged at the proper times (it wasn't just that the replacement was defective).


I tried to check the computer codes myself without the special code reader but I can't get the MIL to flash. I think I am doing something wrong with the jumper wire? It seems like the self test input needs a special plug-in and that I can't just use a piece of Wire?

You should be able to ground the STI connector to the ground terminal in the STO connector.graphic
Customer: replied 8 years ago.

Found the STO, it was right in front of my face the whole time. Here is what it gave me:

code 522 (This one wasn't in my Chilton manual, and I triple checked the flashes)


Also the while I had the jumper wire connected for test mode, the fuel pump cut on and shut off like it is normally supposed to, and the truck would start!

522 is "vehicle not in park or nuetral during self test". Double check make sure it is fully engaged in park. It may be a fault in the trans range sensor.
Customer: replied 8 years ago.

Unfortunately that would require me to fix the torn e-brake cable (Its a manual tranny).


What do you think about this: I just removed the Jumper wire and now the fuel pump will cut on and shut off like it is normally supposed to, and the truck will still start right up. Keep in mind this is with the OLD stock relay.


What is going on here? A bad/intermittent ground at the fuel pump or something?

I am thinking more that the computer was not responding, like a lock up in a PC, and when you put it in self test it is now working normally. I would drive it, keep starting it on a regular basis, (keep your jumper wire with you), if it happens again, I would replace the computer.
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