Hi all, here is the shorter version of my question. What would cause the fusible link (black with orange line) running from the starter relay to burn up? Also where is the GP relay on the block? Thank you. 1991 7.3 IDI

 

I don't know what caused your fusible link to burn up but I can tell you that a lot of fusible link on my truck was burned up when I got it. I never found a cause for most of it and I replaced some of it with wire and some of it with fusible link and haven't had any issues. I kinda think the stuff gets old and crusty and just burns up.

 

GP Relay is on the intake manifold right behind the air intake, next to the CDR

 

Dang pain in the butt to get too as well. It probably just got rusted out....

 

for the fusible links, if i ever had a problem with them i would replace them with self-resetting circuit breakers (available from any parts store). they protect like a fuse but turn back on as soon as things cool down.
but if your fusible links are blown, that usually indicates a short somewhere, and replacing the link with a wire is likely to cause a fire next time that bad part of the wire shorts to a ground. thats what fuses and fusible links are for, to keep the rest of the wires from burning up in that case. i highly recommend against bypassing your fusible links, better would be to visit your local junkyard and pick up a power distribution box from a newer car (with the big fuses), and wire everything that had a fusible link through a big fuse of appropriate size there. does the same thing but is easily serviced if you do have a problem.

 

There was a reason fusible links were used instead of fuses, I can't quite remember the rational, but it was something like they hold better for a short term over-current than fuses do. Kinda like you can get slow blow fuses for your house to run larger electric motors. At least I think thats what the idea was.

I agree its stupid though, as they can't be fixed easily roadside, and can be impossible to detect depending on how catastrophically they blow.

I don't know about the wire color, and there are far too many hanging off my starter relay (stupid ford engineers) but I had the one that goes to the alternator blow when the alternator let out its magic smoke.

 

maybe the goal was to prevent roadside "quick fixes" and force people to get the problem properly diagnosed/repaired

 

I had a ton of issues with my truck and the wiring job the previous person had. I just recently finally replaced the whole cursed wiring harness because of it.

Wierd things can definately happen when wires overheat and melt into each other somewhere where you can't see it.

I have watched numerous rogue grounds arc out on this truck sending pulsations throughout the whole system and not seen one of those fusible links burn for a good 10+ seconds. Enough to see a wire covering heat up, smoke and melt off for a good couple of feet.

So I guess they are slow burners, but I have to wonder if they are going to stop something from lighting on fire. I could see having a breaker being twitchy and annoying depending on use.

They sell the links at the local napa, they list what size wire they are meant to protect. Easy to replace with a basic electrical kit.

Out of all the problems I have had thus far I don't believe the fusible links ended up blowing out, and I am not sure if age has anything to do with it? So I just let it be with the new wiring harness and made sure all loose ends were dealt with. Also did the headlight and running light relay mods and added a 3g alternator to get rid of some wiring.

 

no guys the purpose of fuseable links is not job security for dealership techs.

the above post about short term overcurent draws is correct.
when some electrical devices such as the starter are turned on they have a really big spike in current draw. if they were on a regular fuse they would blow every time you turned the key.

If you burned out a fuseable link i would say that you have a huge draw somewhere that draws for sometime at the high amperage. find out the problem and get it fixed! don't just put a regular piece of wire in it's place. bad things can/will happen.

 

Thanks for backing me up '94IDITurbo7.3, I couldn't quite remember if that was right or not.

The do work at least some of the time. Like I said, mine blew when my alternator let out its magic smoke. One of the diodes broke loose and was rattling around in the alternator case, it had to have been arcing in there for a few seconds at least, as parts of the case and diode eroded away. I actually saw the puff of smoke come out from the side of the hood.

 

yep.

I am in my first semester of one of my auto classes in college and we are learning about automtive electrical. we learned about fuseable links a couple weeks ago. my teacher always says about the magic smoke as well.

 

Fusible links on my 1990 7.3 have burnt out decades ago, all bypassed and haven't had any problems since.


Heres your glow plug controller.