Small electrical fire following glow plug relay replacement - what are these burnt wires?

[ComatoseLlama]

Hello

Today in an effort to decrease the amount of smoke I have on startup, I tried swapping out my glow plug relay with a spare that came with my truck to see if mine was bad. When I turned on the keys a big **** of smoke immediately came out of the front of the passenger side of the hood, clearly electrical smell. For context it was drizzling outside while doing this.

I found these two wires burnt out afterwards, what did I mess up?? I taped over the exposed wire for safety.

One wire is burnt as heck, but in tact, the other burnt completely through and is not connected. The wires come out of the loomed harness.

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Here’s the relay I put in

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Truck works fine, glow plugs seem to be working well, all lights, horn, gauges etc work as well. Nothing out of sorts.

Should I splice in good wire where it burnt out, and go back to my original / a new FoMoCo relay?

thanks

CL

 

[franklin2]

What color are those two wires you are holding? Follow them down in the harness a little bit till you can tell what color they are.

 

[Selahdoor]

They are blue or green in color. Looks light blue.

What is your hand covering up on the wires? Looks like connectors of some sort?

 

[ComatoseLlama]

Both are green wires

Here are photos of where it come out of and goes back into the loom

they have some shrink wrap in them for some reason

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This pic makes me think it’s happened before and they shrink wrapped it

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[chillman88]

I'm wondering if they're fuseable links. Possibly ones that have already been replaced once.

 

[ComatoseLlama]

Hadn’t thought of fuse able links, googled it and this came up, hopefully going to a new relay and new links will solve it

Relay still makes noises like it works though which is weird

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[Selahdoor]

I'd agree about the fusible links. And being shrinkwrapped because it happened before.

Also, yes, it will still work if only one of the fusible links survives.

I would simply pull them out of the loom, all the way to both ends, and replace them.

 

[ComatoseLlama]

Thanks for the help. This forum is awesome

Will update after I give it a go

 

[franklin2]

You guys are figuring they feed the glowplug system? Eventually they should turn back into black/orange wires. The diagram does show two green fusible links.

Problem is, if these are both burnt off the glowplugs would not work. The light in the dash would probably work, and you would hear some clicking, but the plugs would not heat up.

 

[chillman88]

You guys are figuring they feed the glowplug system?

Nope, just figured they'd probably be fusible links given the appearance and mode of failure. Honestly figure it was probably something that got bumped while changing the relay out.

 

[laserjock]

I thought the GP feed wires were yellow? Is that just on the engine side?

 

[franklin2]

I thought the GP feed wires were yellow? Is that just on the engine side?

I thought they were also. Maybe the diagram I looked at was wrong. I seem to remember my wires being yellow also.

 

[ComatoseLlama]

New glow plug relay in

replaced wiring with fusible link

turned it on and immediately they went up in flames again

the two wires come from the black with orange stripe wire coming off glow plug controller, then re enter the harness as black/green and black/yellow

 

[ComatoseLlama]

its the actual harness catching fire, not the fusible link.

here’s the in and out. Straight off the controller as one wire, splits into two then into the harness, originally had 20A fusible link

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it seems the black / green wire is the one that’s going up in flames worse

with the wires disconnected, the glow plug relay clicks around twice a second, and the wait to start light flashes once and then goes off. Plugs definitely are not working.

 

[Selahdoor]

Hate to say it, but you are going to have to tear that harness completely apart. At least enough to get both of those wires completely pulled out and replaced.

Well, that or just remove them on both ends, and add new wires in their place.

Either you have a dead ground at one end or the other, or you have a grounding situation somewhere in the run of the wires.