I've owned the truck in my sig since 2011. I did a complete tune up when dad gave it to me. Plugs, wires, distributor cap, rotor, oil, filters etc. Since then it has gone through four sets of plug wires. It burns through them at the spark plug boot. Of course it doesn't destroy every wire but two or three out of a set. I have tried NGK, Ford replacement wires, Ford racing 9 mm wires and now it has destroyed a set of Bosch premium wires. The truck starts to miss so bad I can barely get up a hill. At night when I check under the hood I can see the blue sparks from the wires that the voltage has breached.
I could only find one reference that MAY have been related and the issue was the coil. I replaced mine and for the first day or so it started very well and ran perfectly. Now, two weeks later, another set of wires is done.
Please help if you can. I'm getting very frustrated.

FWIW I have replaced the plugs three times and the distributor cap and rotor two more times as well, just in case it was something to do with them.

 

My guesses are that the wires aren't properly seated on the plugs, causing arcing between the two, and eating the boot. Next would be a multi spark ignition module installed like an MSD, or something; plus loose wires causing massive arcing. And, lastly maybe too much voltage going to the coil. I'm not an electrical engineer, but maybe too much going in means too much coming out.

Ooh, thought of another one. If the plugs aren't properly grounding the current might try to find the next best thing, and that is through the boot.

And, is there an exhaust heat shield installed? I don't see electrical damage to the metal contact. Could be the heat shield is rubbing on the boot.

 

Very strange.

Only thing I can think of is heat. Maybe get some comparison readings with a truck that is not burning up the plug boots with one of those laser thermometers. Possibly an incorrect heat range of plug? Maybe a timing issue? any pinging? does not look like any sort of contamination that could be breaking down the insulation. Electricity will follow the path of least resistance and normally that would not be through the plug boot.

This should be interesting.

 

Are you putting anything on the plug boots\wires when your installing them on the Spark Plugs?

 

What are you gapping your plugs at?

 

There isn't any white arcing signs and no black / blue melting signs on the terminal itself, it looks like a simple case of too much heat coming off the manifolds. Are your heat shields in place? How close are your wires sitting to the manifold or shields?

You could try some heat socks and see if that works, or you could go for it and buy some of those Accel ceramic high perf plug wire kit.

 

Rodent damage. The little b*****ds do some really weird and destructive things.

 

Thank you everyone for the replies.
As a point of interest I make sure the plug wires are firmly attached to the plugs when they are installed. With the premium Bosch wires there is an audible click when the wires are correctly attached to the plugs.
I have the stock ignition on the truck so no MSD or any other aftermarket distributor or coil. I'm using the recommended plugs as per the Ford dealership. Maybe I could go to one range colder as every time I go to town I have to return up a 20 K hill. It's very hard on the old truck so maybe there is a lot of heat build up in the ignition system? Unless it's extremely hot out, 30 degrees or more my temp gauge doesn't move however.
I believe my timing is correct and is working properly as I don't get any pinging. When I put new plug wires on I use a bit of dielectric grease on the ends of the boots. The Bosch Premium wires already come with a bit of dielectric grease already installed on the boots. My plugs are gapped correctly but offhand I don't remember what the gap is. I use the correct tool for gapping them instead of flat feeler gauges.
When I changed the offending plug wire last night I checked as much as I could to see if the heat shield was touching the boot. It was very close to the boot at the side nearest the front of the engine but not touching it. However the damage to the plug boot is in the same place where the heat shield came the closest to the boot. So maybe the heat shield is too close. If so what can be done about it? I was unable to bend it out of the way at that particular spot. If they need to be changed are the manifold bolts holding the heat shields in place?
I also initially thought the issue could be heat related thus I put Ford Racing 9mm wires. They are reportedly designed to withstand the heat from non shielded headers. They lasted a bit longer than the previous NGK but they still got destroyed.
Today I also checked the input voltage of my coil. The best reading I could get was about 11 volts. I'm guessing it should be 13 or so? I may not have had a solid connection though as my battery shows 13.5 to 14 volts with the truck running. If my input voltage is low would that result in low output voltage and therefore, heat buildup in the plug wires?
I can't figure out how to post a picture from my computer to this post and I can't figure out how to put a new picture into Photobucket so I can post it here. *@&%#$% computers should be simple by now!!!!!!!
At any rate, I tested the voltage at the two input wires on my coil (a red one and a lighter coloured one.) I couldn't get any reading when checking each wire individually to ground but I got the reading when testing both wires with the test leads touching each pin simultaneously. If I did it wrong please let me know. My battery shows 13.5 to 14 volts with the truck running so I'm assuming the alternator is working correctly?
I don't know what a heat sock is and I didn't know there was something such as ceramic plug wires. However, now that I know I'm going to keep them in mind. Thank you for the information.

 

Heat or rodents.

A "hotter" spark plug will not do that to a rubber boot, nor will an ignition system.

I'd look carefully at your exhaust manifolds, you may have a leak somewhere that is shooting directly on your plug boots. I'd also check timing and compression--make sure that truck is running correctly (with stock plugs and wires), and do an internet search for proper routing of the plug wires to make sure you're not getting cross-fire.

Jason

 

[QUOTE=jroehl;15509691]Heat or rodents.

"A "hotter" spark plug will not do that to a rubber boot, nor will an ignition system."

That's good to know.

"I'd look carefully at your exhaust manifolds, you may have a leak somewhere that is shooting directly on your plug boots."

My truck originally had several exhaust leaks from the manifolds. I had both of the exhaust manifolds replaced. Since then I haven't heard any exhaust leaks. Two of the wire sets I had used grey boots and none of them had exhaust residue on them. Consequently I don't believe I have an exhaust leak.

"I'd also check timing and compression--make sure that truck is running correctly (with stock plugs and wires)"

My truck doesn't ping, starts well and has stock plugs and wiring. I believe the timing is OK. Perhaps I'll get a timing light and check it just to confirm. Does anyone have suggestions on a make and model of timing light? I will need to purchase one.
The compression is normal for an old engine. Cylinder 1 -140, 2-130, 3-140, 4-140, 5-135, 6-145, 7-148, 8-125

"and do an internet search for proper routing of the plug wires to make sure you're not getting cross-fire."

One of the first things I did when I got the truck was to read the "Read First" thread. My 7 and 8 plug wires were running side by side and I rerouted them to prevent any crossfire issues. Since then I have ensured none of my plug wires run side by side just in case my issues may have been from cross firing. I have checked and rechecked the firing order and the plug routing and all is good.

These are all good suggestions, thank you.

 

Heat Damage.


I just skimmed over some of your post, I may have missed when you have already checked some of these


Check:


exhaust leaks
running lean
ignition timing.




and oh course heat shields which you said appear ok, which they very well may be, but if it is getting the manifolds that hot you have a fuel/ignition/timing issue somewhere, or at least that is all that pops to my mind..

 

Check the timing late timing will cause the manifolds to run hot. I went with a set of these to help protect the boots on my 460.

 

I'm going to suggest checking the timing as well, if the timing is set back far enough it will be shooting still burning exhaust gases into the manifolds and cause some extreme exhaust manifold temperatures. To use of all things for a comparison....... I'm going to use an old lawn mower I used to have . It backfired and sheared the flywheel key making the timing severely retarded, it would run fine until a load was applied and then everything on the exhaust would start to glow cherry red and if I pushed it I could get parts of the exhaust almost glowing white hot.

 

It looks like I'll be getting a timing light on payday. Eventually I will upgrade my plug wires again and then put those boots on them. BTW, when I pulled codes I got system pass with KOEO and KOER so no running lean issues.

 

Did you happen to check the original wires before you ever replace them to see if they were in the correct location? I have had a truck that had the the plug wires on the cap off by one stud all the way around on the distributor and it was turned to accommodate this for correct timing. I don't know how it would've driven but it did run OK when started for the timing tuneup.