Fuel pump wiring?
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Fuel pump wiring?
My pump (one inside the frame) is hard wired hot to the fuse panel--88 F350 dual tank 4x4 351, 5 spd. I got under it today to find two wires that are cut and hanging out of the trucks wire harness. One is RED w/ BLK stripe, one is BLK only.
The RED w BLK has momentary 12+V power when key is turned on with multimeter's black term touched to the frame. It seems to be about one second and then goes dead. No longer than that. The BLK sees no voltage potential. If I connect the multimeter's terms to the RED/BLK and BLK wires, I see the same 12+V power on for a moment.
This appears to be the original fuel pump wiring. Can someone verify the colors for me and that it powers down after the initial pressure up at KEY ON?
Thanks,
The RED w BLK has momentary 12+V power when key is turned on with multimeter's black term touched to the frame. It seems to be about one second and then goes dead. No longer than that. The BLK sees no voltage potential. If I connect the multimeter's terms to the RED/BLK and BLK wires, I see the same 12+V power on for a moment.
This appears to be the original fuel pump wiring. Can someone verify the colors for me and that it powers down after the initial pressure up at KEY ON?
Thanks,
Senior User
Joined: Oct 2009
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the reason your power could be shutting down after a second is because the wire is cutt and the computer is not telling the power to the pump to stay on. i recently had a similar problem when i went from efi to carburated in my truck. my stock pump would turn on then turn rite off because i was not running a computer to tell it to stay on. i hope this helps and you get your truck running rite
Fleet Owner
Joined: Aug 2005
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From: Easton,Ks
It sounds like the Black/Red stripe wire is working right for an 88 E-series but it should be a BR/W on an 88 F-series.
It should have power on it for one second when the key turned on.
The black wire is a ground.
Here is a diagram if you have two tanks.
/
It should have power on it for one second when the key turned on.
The black wire is a ground.
Here is a diagram if you have two tanks.
/
Posting Guru
Joined: Jan 2002
Posts: 1,346
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From: Baltimore
Subford beat me to it.
Manual shows the wire is Pink/Black which is 12 volts for the frame rail mounted pump and the same wire turns into a Red/white wire at the Fuel tank slector switch which then feeds the front intank pump by a Red wire and the rear intank pump by a Brown/White wire..
Black is ground.
If you only have a single tank. The Pink/Black wire is 12 volts for both the frame rail and intank pump.
The reason you only see 12 volts for 1 second is the computer doesn't see any reference pulses coming from the distributor. This indicate the engine is not running or being cranked by the starter so it disables the fuel pump relay.
Manual shows the wire is Pink/Black which is 12 volts for the frame rail mounted pump and the same wire turns into a Red/white wire at the Fuel tank slector switch which then feeds the front intank pump by a Red wire and the rear intank pump by a Brown/White wire..
Black is ground.
If you only have a single tank. The Pink/Black wire is 12 volts for both the frame rail and intank pump.
The reason you only see 12 volts for 1 second is the computer doesn't see any reference pulses coming from the distributor. This indicate the engine is not running or being cranked by the starter so it disables the fuel pump relay.
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Thanks guys. Yep, it is PINK/blk after looking again. Those are very helpful schematics. I need to get a service manual for this thing I guess.
Awesome, now I can wire it as it should be. One more item off the list I hope.
Awesome, now I can wire it as it should be. One more item off the list I hope.
Senior User
Joined: Oct 2009
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if you still have problems you can hard wire your fuel pumps to a switch then you just gotta turn it on and off manually this eliminates any guessing with wires and i still have my notes from when i did mine if this becomes your only option.
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Junior User
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Well, the wiring is still good it appears. I used the cut wires and it powered the pump for a second and quit. I started it and it runs. It's idling like it should right now to be sure it doesn't shut down. Now I'm on to the issue of the wrong transfer case that's in place.
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i need help with the i think its the fuel sending unit wiring i have 4 wires black, orange,red, and blue the connector is flat black and square and fits over an oblong opening on the top of the fuel pump can neone help thanks i have a 1993 f-150 300-6 2wd 2 tanks i am working on the front tank and the fuel guage not working
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From: Kentucky
