After 2.5 years of flawless service....

[V8Astro]

My '08 caught on fire this morning. This truck has never missed a beat despite what it's been thru. During the last week my glowplug system had been acting funny. By funny I mean it was holding relay closed for a long long time compared to what it had been. The resistor pack started to smoke one morning it stayed on so long. I was able to get out and check the relay. It wasn't stuck. The card was holding it on.

The GP's were 2 years old so I decided to change all 8 and check the rest of the system. I followed the TM's. Everything checked out fine except the resistor. TM said .28 ohms (which seems really low) and mine measured at 1.4ohms. I decided it was time to bypass it since everyone does anyway.

While I was at it I did the doghead stater relay mod just because a few days prior the OE starter relay failed to engage(or so I thought). I figured it was on borrowed time so I changed that too. I drove the truck a few times after the dohead mod and everything seemed GTG.

This morning I cycled the key let the GP card so it's thing. Everything seemed ok. I turned the key to start...and nothing. Then I heard a bang and a lot of smoke rolled up from under the hood from the GP relay area. I got out to check and the wiring behind the driver-side cyl head was on fire. The house and the garage were locked up so I put it out with the dogs water dish. I know, I know...water on an electrical fire. I didn't get a chance to sort thru the mess as all the running around like a maniac made me late for work.

All I can say is FHGSGFHGSGFH! I've been on the forum as long as I've had the truck. I've read some interesting things and I've always thought "man I'm lucky everything on mine works!"

 

[engineman2]

Wow that's terrible. So the wiring harness running up the drivers side of the engine toward the drivers alternator is cooked? Did you find out what made the bang noise you described?

 

[V8Astro]

Not sure what the bang was. The big lump of wiring loom / harness at the rear corner of the head is what was on fire. I didn't get to investigate too much. I will update as soon as I can get some diag time in it.

 

[85CUCVtom]

Sorry, that's a real bummer. Keep us posted on what you find.

 

[V8Astro]

I found that most of the wiring was ok. It was the loom the was burning.Some of the small wires in the loom were crispy so I cut those sections out and repaired them.

I started my investigation at the starter. Unhooked the purple wire and pulled it up to the top so I could inspect it. It looked ok. I unwound the harness and the purple wire looked fine all the way to the tee under the master cyl. At this point I was perplexed. It got hot enough to catch fire but the purple wire looked fine. Instead of dismantling the entire harness I decided to check resistance. I just installed the doghead relay which has a convenient post on the back for the multimeter clip. I check resistance from there to the end of the purple wire. 65 ohms!

As I was fussing the starter end of the wire I noticed the resistance changed. I performed a "wiggle test" and found a bad connection at the firewall pass-thru to the fuse block. I noticed some black sooty smears under the connector as I was disconnecting it. YUCK. My theory is there was a bad connection, the 1984 dielectric grease(that now looks like roofing tar) got so hot it flared up and ran down on to the loom. The foam gasket was between the block and connector was toast. The bottom of the connector was also scorched but not deformed.

I scrubbed both sides of the junction with a wire brush and brake clean. Cleaned with windex and blasted clean with shop air. Put it all back togther and got .8ohms from relay to starter.

I'm going to quote another member(can't remember who). "If it's rubber replace it. If it's electrical clean it." <---YEP!

Headlights and dash lights are brighter now too!

 

[engineman2]

Sweet, glad to hear it you've discovered the source of your troubles!