I opened the hood while the truck was running in total darkness and saw that all 8 spark plugs were arcing to the heads. It wasn’t a fireworks show, my eye had to adjust for a few seconds before I could see it really well.

Anyway, the Champion plugs that I’ve always used are have less than 1k on them. The wires are 8mm and boots fully seated, I’ve forgotten I’d they are magnacores or not. I do remember they weren’t cheap. And as far as I know the coil packs are original, I haven’t changed them in my 10 year ownership. Given the condition of the truck when I bought it I seriously doubt the previous owner changed them.


Suggestions?

 

Put a light amount of di-electric grease around the spark plug wire boots. Not on the leads itself (should look up the proper application). This might be enough insulation to prevent the arcing. That's what I would try first.

 

That's weird. Definitely waiting for the story to this... also do coil packs get replaced with age? I haven't replaced any of them. Ever.

 

Rock Auto had STI wire sets for 2.90 the other day for D1's (scored on that deal!). Rock Auto has D2 wire sets for like 25.00. If they're 10 years old you got your $$ out of them. The boots will eventually become either rock hard and extremely brittle or the leads will rip off whenever you try to remove them.

 

The upon visual inspection the wires are good. Nothing brittle, connection inside the boot still bright free of corrosion .

 

This is the easiest and cheapest first step. Most times this is from where the spark is coming. Only once have I had the plug itself be the problem.

 

I’ll do that first for sure. I just want to be clear that the arcing is not from inside the boot to the head, the arcing is from the hex base.

 

Couple things, it seems unlikely it is the coil packs if all 8 plugs are behaving like this. (There are 2 coil packs, with independent electric inputs) Replacing them still might be a good idea though, whenever I replace the wires in a new disco I do the coil packs as well. Voltage from battery OK? Try swapping in an old/different spark plug in one socket and see if it also happens.

 

And the rubber boot is tight on the insulator? That’s a wild one for sure!

 

Unless there's extreme corrosion on all of the threads which is near impossible, the spark is not coming from the he base. There is no difference in potential between there and the head; they are bonded together. That is the grounded portion of the spark plug.

I would suspect that it is indeed coming past the boot and only looks like it's coming from the base.