Engine fuse blowing on startup - help diagnose (1 Viewer)

[Kschep]

So my engine fuse keeps blowing on my 76 on startup...how can I diagnose and fix this? Super frustrating...engine keeps rolling obviously and then I get some smoke coming from the ignition pictured .. assuming because the fuse is blown and engine still rolling creates problem ... Am I incorrect in associating these things together.

 

[bhsdriller]

Mine is a 75 with a 2F from a 78 but I was having the same problem. The main thing I noticed was that the idle solenoid was powered from this circuit so mine wouldn't run. I had to wire the solenoid directly to 12v power then it was fine.

Like this mine ran perfectly.

Ultimately it was a wire crossed at the alternator. Was blowing the fuse and in conjunction the alternator wasn't charging so my battery kept dying.
Fixed the wiring at the alternator and no more blown fuse and charging correctly.

It's shorting out somewhere

 

[Cromagnon]

These problems may be related. Look at the correct wiring diagram and trace the wire from the engine fuse to the associated device(s), should be a LR wire and goes to the voltage regulator at least, and troubleshoot those.

What are all of the wires on the positive terminal and the screw going to? The less extraneous wires you have to deal with will be better from a troubleshooting point of view, let alone safety.

 

[Kschep]

[\QUOTE]
What are all of the wires on the positive terminal and the screw going to? The less extraneous wires you have to deal with will be better from a troubleshooting point of view, let alone safety.
[/QUOTE]

Well it’s aftermarket audio and then air compressor for ARB lockers ... so there a lot going on, I want a 2nd battery set up

 

[Kschep]

Mine is a 75 with a 2F from a 78 but I was having the same problem. The main thing I noticed was that the idle solenoid was powered from this circuit so mine wouldn't run. I had to wire the solenoid directly to 12v power then it was fine.

Like this mine ran perfectly.

Ultimately it was a wire crossed at the alternator. Was blowing the fuse and in conjunction the alternator wasn't charging so my battery kept dying.
Fixed the wiring at the alternator and no more blown fuse and charging correctly.

It's shorting out somewhere

Wow your giving me some serious hope ... sounds like just what would get my truck going...

 

[Kschep]

[\QUOTE]
I had to wire the solenoid directly to 12v power then it was fine.
[/QUOTE]

How did you go about this if you don’t mind me asking...going to do this today to see what happens

 

[bhsdriller]

Not ideal but I took a wire straight from the positive on the battery. This way also sends power directly to the solenoid at all times and you can get some dieseling at shut off. Under normal operation it's only getting power while the key is on.

I've read that you can take 12v switched from the coil as well.

With saying this there's no way to know if it's what's causing your problem but for me it let me drive it.

 

[Kschep]

Not ideal but I took a wire straight from the positive on the battery. This way also sends power directly to the solenoid at all times and you can get some dieseling at shut off. Under normal operation it's only getting power while the key is on.

I've read that you can take 12v switched from the coil as well.

With saying this there's no way to know if it's what's causing your problem but for me it let me drive it.

That’s fine with me...I’ll go get an in-line fuse line and attach it straight up to the battery - screw it - at this point I’ll try anything. I’ve been fixing issues for a while - lol I’m ready to drive this thing.. I keep tinkering

 

[BeerM3]

Totally just a WAG but it looks like a metal hold-down for the battery is on the negative terminal? Is that bridging close enough to the positive cable terminal to arc when the engine's vibrating? Or is there a bare end of one of the extra B+ leads for the locker, audio, etc.?

 

[Kschep]

Totally just a WAG but it looks like a metal hold-down for the battery is on the negative terminal? Is that bridging close enough to the positive cable terminal to arc when the engine's vibrating? Or is there a bare end of one of the extra B+ leads for the locker, audio, etc.?

Good thoughts - yes it’s close but the really close part is just plastic - the actual metal are angled inward at the middle to prevent this...I didn’t do it but after you pointed it out I looked and that’s what I noticed...as far as audio and other stuff attached, I know it’s a clusterF I need to clean it up but that’s not my issue (car dieing when no choke applied/ engine fuse blowing on start up everytime - replaced: alt. ; idle solenoid ; rebuild carb ; fixed what I thought were vacuum leaks but nothing) - so I’m here at this hoping

 

[Kschep]

Ok snipped the wire - attached inline fuse - attached all the positive battery terminal ... solenoid clicks perfectly ... good
BUT - went to check the new fuse I put in the fuse box (not the new in-line) and there it was engine fuse blown again on start up...

where do I go from here? I don’t know how my alternator wires could possibly be mixed, it’s basic..not thinking that’s it but s*** maybe

 

[bhsdriller]

Did this just start happening? You should be able to start/drive it now?

Get a wiring diagram as it's a short somewhere that keeps popping the fuse.

 

[Kschep]

ya it still won’t idle without choke.. it’s a common problem that could be caused by so many different things..I’m going attention to all the other threads of the same issue. But trying to figure out my own

 

[Kschep]

I can drive it though...trying to get it to smell a little less now. Backed out my idle mixture nothing ..

 

[Cromagnon]

Read post #74 of this THREAD. The field and earth wire were swapped at the alternator.

 

[bhsdriller]

Easy test you can unplug the alternator connection and see if the fuse holds or blows

 

[Kschep]

Read post #74 of this THREAD. The field and earth wire were swapped at the alternator.

hyperlink doesn’t work?

 

[JohnnyC]

Are you sure your not just chasing a bad fuse block? Had you removed the fuse block ... cleaned all contact areas ... dielectric... and reinstall it?

 

[Cromagnon]

Oops!! 1975 FJ40 Instrument Panel Not Working