I have a wiring issue 95 f350 460 instantly will blow fuel pump fuses EVEN if the tank switch itself is unplugged and if the relay is out also. And if the switch is plugged in it will do it on either tank. So that would mean the wires under the fuse box are shorting out correct. And if that is the case how do you pull the fuse box off the metal bracket.

 

Which fuse is blowing, one in the middle row under the hood? When the radio capacitor on the coil of my '94 F-150 shorted out, I could hear the fuel pump run for a split second before it would blow, I think the third fuse from the driver side fender in the middle row in the fuse box under the hood. I thought I had a problem with the fuel pump system, I would have never figured it out if I had noticed the bad wire on the capacitor on the coil.

I suspect your problem may be with the ignition, but I sure could be wrong.

 

Check the fuel relay socket for lose wires or shorted wires.

Check continuity on each fuel relay socket wire to ground, looking for a short.

Fuse "O" 20A ?

 

It be the big fuse second one down on the left row. And where are all the grounds to check

 

Not necessarily, It could be a wire leading away from the Fuse Box.

check your Inertia device wiring as well.

 

The only time i could get it to stop blowing fuses is unplugging the fuse box from the dash harness in the firewall. Altho strangely i put a different relay in and new fuse turned the key and the pump primed up once before it blew the fuse again

 

Yes it sounds like a problem with the Fuse/relay box.

Some information on this thread:
https://www.ford-trucks.com/forums/1...ution-box.html



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So i pulled the fuse box apart and still see no issue. The only time it wont pop the fuse is when the dash harness is completely unplugged. I unpluged the frame harness and it still pops so that eliminates it being the frame harness. Idk what to check for now

 

But you did say it blows the fuse "O" with the fuel pump relay pulled out and not in the circuit, right?

 

Playing devils advocate, pulling the frame harness doesnt mean its clean. You can have multiple spots with failed wiring/insulation. Pulling fuses and plugs can have you chasing your tail til the point of madness! Get a decent multimeter with a continuity function and chase down your short(s).

 

no fuse I on the left side

i just relooked at that diagram i is the one that blows but the only thing that quits when it blows is the fuel pump. So this whole time ive been looking at the wrong ****

 

When you unplug the dash harness the PCM Power relay does not operate is why the fuse "I" does not blow.
So it sounds like you have a short to ground on the Red #361 wire or something that it feeds.

Here the wiring diagrams:




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Im not good with wiring or wiring diagrams at all. Where would that red wire be

 

The Red wire runs all over the engine and also goes to the transmission if you have an E4OD.
It starts out at the PCM Power relay and goes from there to all of the solenoids, relays and the PCM Computer.
Just follow the red wires in the diagrams I posted above.

 

yes but the fuse still blows if i disconect the engine harness from the main harness so i know thats ruled out so its either gotta be in the dash or in the engine bay harness but ive run out of leads