30amp Maxi fuse for fuel pump keeps blowing.

[Eddo Rogue]

Not sure if this is the right section, but this fuse keeps blowing, so far only during hard off roading.

It seems to only do it when in 4low, the right flex or jolt, and she will stall out and burn the fuse.

Its the 30 amp maxi fuse for the fuel pump. Stalls out and blows the fuse if/when I hit a bump, dip or hill somewhat aggressively.

I ran out of 30 amp and now have a 40 amp in there, but have not driven it since other than to park.

Could it be the battery hitting the hood or something? seems secure idk. No clue here where to start....electrical ain't my thing.

Long shot but maybe my motor mounts are bad and causing stuff to move around? I have been doing a lot of motor mounts and steering/suspension stuff lately...seems to be a trend.

 

[Uncle Gump]

The only way that fuse blows is a hard short to ground on the output side of the fuse.

 

[Eddo Rogue]

The only way that fuse blows is a hard short to ground on the output side of the fuse.

I understand, but not sure what that means lol.

So maybe the fuse box is jumping around or there is an exposed wire under it or something?

Hoping I won't need a multi meter. My least favorite tool.

 

[Uncle Gump]

Yeah... it would be some exposed wire on that circuit touching ground.

I would be careful testing using a 40 Amp fuse on that 30 Amp circuit. I would use a 30 Amp circuit breaker.

Get the circuit working and start wiggling that harness and see if you can make it blow. Check places where that harness crosses metal body panels etc...

 

[rusty ol ranger]

You have an exposed, broken, or otherwise dicked up wire somewhere between the fuse box and the pump.

 

[Eddo Rogue]

Yeah... it would be some exposed wire on that circuit touching ground.

I would be careful testing using a 40 Amp fuse on that 30 Amp circuit. I would use a 30 Amp circuit breaker.

Get the circuit working and start wiggling that harness and see if you can make it blow. Check places where that harness crosses metal body panels etc...

Copy that, will do.

Yea I know, the 40 amp was just all I had to get me off the hillside and back into the driveway to park.

I have since picked up a few more 30 ampers for this. Thanks Unc!

 

[rusty ol ranger]

@Uncle Gump it wouldnt possibly be some weird inertia switch issue would it?

 

[Uncle Gump]

The inertia switch interrupts that circuit not shorts it to ground.

But I guess anything is possible... even if it's highly unlikely.

 

[sgtsandman]

Sounds like a wire is grounding out to the truck somewhere. Check and chase what you can from under the truck but you may need to pull the bed to check the rest.

As far the battery contacting something, if it did, it would blow more than the fuel pump and would probably leave a burn mark where it made contact.

 

[Roert42]

First thing first, find the wires that run from the fuse/ relay to the pump. Chase them down and do a visual inspection to make sure it's nothing obvious, probably easier with the bed off, but you'll be under the truck at some point anyway.

Like gump said, start shaking the wiring around with the truck running and see if you can get the fuse to blow, that should point you at least to the general part of the circuit.

I would bet there is a pinch or nick in the wire some where, so once you find it you'll have to cut it back and splice in some good wire with heat shrink ect.

 

[pjtoledo]

@Uncle Gump it wouldnt possibly be some weird inertia switch issue would it?

the wires at the inertia switch do like to overheat. new pigtails are available.

 

[dvdswan]

From the description you have I would look at a wire loom that has broken loose and has chaffed the wires. Guessing, since you're in Burbank, you do lots of desert racing style offroad and possible KOH stuff. Dry heat, time/age, plastics are brittle, so clips may have broken. Engine harness and underbody is where I would start with @Uncle Gump 's suggestion.

 

[Eddo Rogue]

Do you guys think it could possibly the fuel inertia switch tripping the fuse? I smacked it around a bit testing it when I was diagnosing the no start after falling in the non backfilled pipe ditch (before finding the blown fuse)

I'm having a hard time getting it to replicate the fuse blowing again. Seems like it only does it when it wants to, over just the right kind of terrain impact. I bumped around quite a bit parking up an embankment to do some car shuffling in the parking area of driveway, no fuse blew.

Would it be bad idea to just bypass the inertia switch? and least for now to rule out?

 

[Eddo Rogue]

Kinda left this thread hanging as I am still chasing the problem.

wiring under body and inner fender looks fine.

I did read the common place for a short the wiring inside the kick panel....is this worth looking into?

Also could it be my inertia switch causing it?

I drove it the other day and it ran great on highways and streets, soon as I jarred it a little going up my dirt hill it blew again. Seems like the right combo of bumpy incline will trip the fuse.

 

[sgtsandman]

Kinda left this thread hanging as I am still chasing the problem.

wiring under body and inner fender looks fine.

I did read the common place for a short the wiring inside the kick panel....is this worth looking into?

Also could it be my inertia switch causing it?

I drove it the other day and it ran great on highways and streets, soon as I jarred it a little going up my dirt hill it blew again. Seems like the right combo of bumpy incline will trip the fuse.

I would. Wires rubbing on steel don’t care where they are located. A short is a short. And it sounds like you have a wire with a bare spot.