engine harness replacing (harness fire)

[krisking94]

So as I posted awhile ago my harness caught fire from what I believe to be a short in it somewhere. And while pulling the old harness out I noticed there were two connectors that looked like they were melted on the inside (where the wires come together and go into the plastic piece. Idk if this has to do with my harness catching fire or something else. It's not melted from the fire as the other connectors next to it have no heat\flame damage. Here are the two connectors. I believe they go into resistors but not positive. If anyone could tell me what they do I would greatly appreciate it. Do not want to have another engine fire I got too lucky this time

 

[krisking94]

Here is what I am talking about

 

[krisking94]

And this is where the fire happened. Have to look a bit but it's to the right of the ac compressor and just above the down pipe

 

[GNVenom]

Those connectors aren't melted. They are the AC and FUEL relay connectors, filled with tar (gorilla snot) from the factory. That was the original sealant that GM put on those, along with the big bulkhead, fan relays and delay relay connectors.

 

[GNVenom]

My guess is your harness burned because the oval conduit clips failed, causing the oval conduit to fall onto the downpipe. Once the heat burns through, it causes a short to one or more of the main 12 gage feeders, causing the catastrophe.

I have been saying it for years; replace those plastic conduit clips (there are two of them) and it will eliminate this potential disaster. Cheap insurance.

 

[krisking94]

My guess is your harness burned because the oval conduit clips failed, causing the oval conduit to fall onto the downpipe. Once the heat burns through, it causes a short to one or more of the main 12 gage feeders, causing the catastrophe.

I have been saying it for years; replace those plastic conduit clips (there are two of them) and it will eliminate this potential disaster. Cheap insurance.

I was thinking that do about the plastic clips. But before the fire happened about a week before my car was cutting out while driving. It would shut off. CEL came on then car would come right back on all under 2 seconds. And one time it didn't come back on so I pulled off to the side threw it in park then tried to turn the car back on. But right when I turned the key over flames appeared.

 

[krisking94]

Anyone?? I feel like there was more to my harness catching fire other then the plastic brackets failing. Like I said a couple days before it happened my car was cutting out while driving and electronics would cut out with it along with CEL light coming on

 

[GNVenom]

Nope. That's all it takes to trash a harness.

 

[krisking94]

Nope. That's all it takes to trash a harness.

1 clip is intact and the other is halfway melted. So I don't think they failed. And that does not explain the car cutting out

 

[scgnx2]

If you zoom up on the pics of the connector housing where the wires exit there are signs of a connector failure (burn marks, melted plastic). Unplug the connectors and post some pics of what you see.
If the contact interface sees high resistance ( ohms) due to corrosion or metal fatigue, etc. The interface can physically ignite on circuits which are feeding power. Remember these connectors are nearly 30 years old. That might explain why you were seeing electrical issues prior to the fire.

 

[GNVenom]

Was the oval conduit burned thru? Any telltale marks on the downpipe?

Connector failures generally won't start a fire; the materials they used in the 80's would melt but not sustain a flame. A persistent short circuit will definitely melt down the harness and cause a fire, mostly because the plastic has usually been soaked in oil from years of leaks and vapors.

Regardless, a new harness is your best bet.

 

[gsgnnut]

There appears to be arc flash marks on the down. Pipe under the oval conduit. Look and see if it arced out there. That would cause a cascade effect of electric faults and could easily start a fire upstream. Also I believe the conduit strap appears failed but could be due to the fire but any arc. Marks on the down pile will confirm the cause.

 

[krisking94]

If you zoom up on the pics of the connector housing where the wires exit there are signs of a connector failure (burn marks, melted plastic). Unplug the connectors and post some pics of what you see.
If the contact interface sees high resistance ( ohms) due to corrosion or metal fatigue, etc. The interface can physically ignite on circuits which are feeding power. Remember these connectors are nearly 30 years old. That might explain why you were seeing electrical issues prior to the fire.

Okay will take some/post them after work tomorrow

 

[INEEDAGN]

Shouldn't the fusible links by the starter blow in this situation, preventing a fire? I mean I've seen them start fires without blowing before but it was cheap pvc coated wire that melted instantly. If they don't burn out, why the hell do they even exist?

On my 84/86 conversion the fusible links were all half assed so I lengthened those wires with quality cross link insulated wire and put new fuse links behind the battery where I could get to them. This makes me want to replace them with traditional fuse holders but don't know what amp ratings to use.

 

[GNVenom]

The battery cable that goes to the starter is not fuse-linked. If the cable should come in contact with the downpipe (which happens when you use an aftermarket down pipe along with the stock length cable) you have a major short and impending fire on everything that had been oil and grease soaked in the vicinity.

And, fuse links are only there to open in the event of a dead short "crowbar" situation. If there is a short that's intermittent or not directly grounded, heat may build up on it, causing a meltdown, but fail to open the link.

If your oval conduit is mostly intact and not down-pipe-burned thru, then you should look at that positive cable.

 

[krisking94]

The battery cable that goes to the starter is not fuse-linked. If the cable should come in contact with the downpipe (which happens when you use an aftermarket down pipe along with the stock length cable) you have a major short and impending fire on everything that had been oil and grease soaked in the vicinity.

And, fuse links are only there to open in the event of a dead short "crowbar" situation. If there is a short that's intermittent or not directly grounded, heat may build up on it, causing a meltdown, but fail to open the link.

If your oval conduit is mostly intact and not down-pipe-burned thru, then you should look at that positive cable.

I'm going to take some more pics of the engine bay once I get home n a couple of hours and I'll post them. I appreciate all of you're input.

 

[krisking94]

If you zoom up on the pics of the connector housing where the wires exit there are signs of a connector failure (burn marks, melted plastic). Unplug the connectors and post some pics of what you see.
If the contact interface sees high resistance ( ohms) due to corrosion or metal fatigue, etc. The interface can physically ignite on circuits which are feeding power. Remember these connectors are nearly 30 years old. That might explain why you were seeing electrical issues prior to the fire.

Here are the pics

 

[krisking94]

The battery cable that goes to the starter is not fuse-linked. If the cable should come in contact with the downpipe (which happens when you use an aftermarket down pipe along with the stock length cable) you have a major short and impending fire on everything that had been oil and grease soaked in the vicinity.

And, fuse links are only there to open in the event of a dead short "crowbar" situation. If there is a short that's intermittent or not directly grounded, heat may build up on it, causing a meltdown, but fail to open the link.

If your oval conduit is mostly intact and not down-pipe-burned thru, then you should look at that positive cable.

Pics sorry for the late response