Hey everyone, I need some help. First of all my pickup is a '93 F250 w/ 351w EFI
auto, 4x4, reg cab long bed. It has dual fuel tanks and I believe my problem is somewhere in the wiring for the fuel pumps or for the fuel injectors. So last week as I was pulling into the driveway my pickup died and I thought it was out of gas, but after filling it back up and when turning the key on I noticed I couldnt hear either fuel pump running. So I started checking for a burnt fuse under the hood and one of the 20 amp fuses in the far left of the fuse box was shot, so I replaced it and drove it for about 5 min and it blew the same fuse again. So I started looking for a cut or frayed wire. I unplugged the main wiring harness that runs both tanks and the tail lights and took it completely out and went through each wire looking for a place where it could short out. But I found nothing. So just this last Saturday I ran a wire from the front tank fuel pump and ran it up to a toggle switch in the cab so I could manually turn the fuel pump on. This seemed to work, but after about 5 min of driving again, the pickup died, but the fuel pump was still running because of the toggle switch. I tried to start it but even though the fuel pump was pumping it wouldnt even sputter. So im at a loss right now as what to do. Any advice or suggestions would be greatly appriciated.

 

What fuse number was blowing? It should be labeled on the fusebox cover.

 

Welcome aboard.

So the same 20A fuse blew? Or did the truck just die? What else is on that fuse circuit?

Either not related, or something else is blowing the fuse and taking power from ignition?

 

Yea its the same 20A fuse, and the truck only dies when the fuse blows. Im not for sure what is on that circut either. And Im not for sure what fuse number that is because the fuse box cover doesnt have the diagram, at least I dont think it does, but I'll take a look tonight.

 

The cover just has numbers on it - the explanation for the numbers is in your owner's manual.

 

I can look in my Chiltons book tonight and see what else is on that circuit that could be shorting.

Cover should have numbers on it(either inside or outside). Owners manual will then tell you what is on that circuit.

 

Here is what the fuse box looks like:


Here is what they do:


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Thanks for the pic and the diagram. It is the I fuse. So now I just need to know where to look for the problem. Anybody know where I should start?

Actually I got to looking at the pic and the Fuel Pump Relay on my pickup seems to be burnt on one of the plugs. So I think I'll go get a new relay and see if I can get it running

 

Check the socket that the relay plugs into if your relay has burnt blades. On my old 94 the fuel pump relay socket was bad causing high amps. The connector to the fuel tank was also resistive and I replaced that too.
YMMV
rikard

 

You may want to check the fuel pressure. A worn pump can still run but draw too much current for the circuit and blow the fuse.

Since you have it straight wired now there is no fuse to blow, but just because its running doesn't mean its putting out enough pressure/volume.

Might want to check the fuel filter as well, if its not letting fuel through the pump wouldn't be cooled by the fuel and can get hot and draw more load.

 

Fuse "I" does not supply power to the fuel pump.
Fuse "O" is the power supply fuse that provides all the power to run the fuel pumps.



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Well I replaced the fuel pump relay and put a new fuse in and it did the same thing again. Its weird, because if a worn fuel pump motor was causing the problem, I couldnt imagine that both pumps would have the same problem, because no matter which tank I'm running on, I still blow the "I" fuse. And when the pickup dies the fuel pump that I have wired to the toggle switch is still running, so I'm guessing that whenever the fuse blows, its shutting some part of my ignition off, coil? injectors?????

 

As I said above. The fuel pump is not powered by fuse "I".
So the fuel pumps would have nothing to do with your problem.

 

I would like to apologize, I should have read the posts more carefully before responding.

Last week was a strange week regarding fuel pumps for me. Seemed like everything that came in the shop last week needed fuel pumps. Had to drop a fuel tank every day for 5 days in a row, not fun.

One of which would blow the fuse, but would run with jumpers but only put out about 20psi at the pump and had a mostly clogged fuel filter so this sounded pretty similar, except for it being the wrong fuse that is.

 

Well I took it to the mechanic shop today to see if they can get it running since I dont have time to work on it, so if it gets fixed I'll let you know what the problem was. But thanks to all your guys imput and suggestions!