Thread: mustang fuel pump relay

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I have a friend who has an 86 Mustang GT After he shuts the car off his fuel pump stays on. I'm wandering where we can find the relay to check that?

First, let me say that I don't know ANYTHING about EFI, but the problem would not seem to be in the relay because it's doing its job properly, sending current to the pump. I would think you would want to chase the wire back from the relay and find out what's powering the relay and why it won't power-down.

I was just reading that some aftermarket pumps use a wire directly from the battery to the relay and some speed density to mass air conversions run a different wire also. Maybe someone has backyard-engineered the car before your friend got it.

http://www.racetronix.com/Racetronix..._Pump_Kit.html

http://www.coolcats.net/tech/advanced/massair.html

anyway, the relay should be in the trunk behind the passenger seat or maybe hung from the rear support laces of the seat.

I was going to go through the wiring if he ever shows up. I've seen a few relays stick before. I was going to check it for continuity before energizing it and then see if there's a short somewhere causing it to be energized

No clue where the relay is. We pretty much gutted the interior and I followed the lines all the way to somewhere up underneath the dash board. Did find a connection in the wiring harness up underneath the the driver's side kick panel that we can disconnect to stop the pump. They hayne's manual just sucks when it comes to electrical. The color to the wiring was even off. I'm about to do some backyard engineering with a toggle switch and some wire.

Originally posted by firebird45331
No clue where the relay is. We pretty much gutted the interior and I followed the lines all the way to somewhere up underneath the dash board. Did find a connection in the wiring harness up underneath the the driver's side kick panel that we can disconnect to stop the pump. They hayne's manual just sucks when it comes to electrical. The color to the wiring was even off. I'm about to do some backyard engineering with a toggle switch and some wire.

relay is located on firewall under air intake...
only one there... eay to find on mine, cuz it has a cold air setup...
I had the same problem in my 90 5.0 lx... it ended up frying the pump as well.... literaly...
replaced the pump AND relay, worked fine for a day, and now the pump does not work at all....
when i figure it out, i will post again...

for 86 at least it was under the driver's seat. we took it out and tested it and it was good. We took it to autozone and their relay had a different plug than ours did. After we had it out and messed with it the problem never happened again.