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My truck is destroying every coil I plug in to the #6 hole within about 5 minutes of driving. I assume they must be heating up inside, expanding and melting the epoxy, then poof. I have tried replacing the spark plug, but I just don't understand what could be causing this to happen with a simple two wire coil. I did find one other similar thread and someone suggested PCM - which I have considered, but there was no follow up. I would think that if there was a short, the truck would never run right, but it runs fine until the meltdown.
It has done this to 3 different coils now. The 4th one that is in there now has just started to misfire, but not explode.
Strange indeed.
The coil like all the others is fed 14 volts through a fuse.
The other side of the coil winding is connected to the PCM and the solid state coil driver.
The driver SCT is triggered by the program to provide ground to the coil.
If the driver circuit has an issue that never fully opens the coil circuit, the coil continuously has current flow.
The combination of engine heat and current flow will over heat the coil.
.
Here is the way to test the coil driver or for a ground in the harness to the PCM..
The driver normally has about 10,000 ohms +/- to ground designed into it's circuit as a test parameter.
Use an Ohm meter to look back on the coil driver lead from the coil plug at this resistance value.
With coil overheating expect a low resistance or near short to ground condition that will cause continuous current flow raising the average running value hence overheating the coil.
Good luck..
Strange indeed.
The coil like all the others is fed 14 volts through a fuse.
The other side of the coil winding is connected to the PCM and the solid state coil driver.
The driver SCT is triggered by the program to provide ground to the coil.
If the driver circuit has an issue that never fully opens the coil circuit, the coil continuously has current flow.
The combination of engine heat and current flow will over heat the coil.
.
Here is the way to test the coil driver or for a ground in the harness to the PCM..
The driver normally has about 10,000 ohms +/- to ground designed into it's circuit as a test parameter.
Use an Ohm meter to look back on the coil driver lead from the coil plug at this resistance value.
With coil overheating expect a low resistance or near short to ground condition that will cause continuous current flow raising the average running value hence overheating the coil.
Good luck..
Great info! Thanks, I'll try that. If I find the resistance to be way off, I'll pull the PCM apart and see what I can see. COP6 is conveniently located on pin #1 for the V8 and V10.
I think I figured it out. I have been troubled with the most evil of all creatures on this planet - the packrat. The truck is my only vehicle that parks outside and I found some chewed wires at the PCM behind the battery. I repaired what I could see, but none of them were to coil 6. However, I wired up a LED in the #6 circuit, turned the key on and when the truck is hot, I wiggled the harness and the light lit. So I had the signal wire from the PCM grounding intermittently. I just ran a new wire from the PCM to the coil and I think that will cure it.
I'm glad I have a pile of coils for testing! I melted 6 of them LOL. The Motorcraft had red epoxy inside where all the others had black.
Here in Aridzona, we too have problems with packrats depending on where we're located.
One solution that helps is to leave the hood open when the vehicle is parked. Packrats are looking for a nesting place and if the hood is down, they think they've found the perfect home. And as you posted, they love to chew on wires and small diameter tubing. They'll also pull out insulation to make a nest.
If you can't, or don't want to leave the hood open, a better solution (one I've used) is to hotwire a bright white LED to the battery and mount it inside the engine bay so it illuminates the engine compartment with the hood closed. The light will be on all the time and makes that area uninviting to packrats. An LED doesn't pull too much power, so unless the vehicle sits for a prolonged time, the battery is not depleted.
I've tried packrat baits and found them ineffective.
I'm in Tucson at the base of Mt Lemmon on 1.5 acres, so the little bastards are everywhere. The hood open thing didn't work. I'll try the LED.
One time, the little devil chewed through a grommet, entered the cab and ate MY SEATBELT, then made a nest with the material in MY SUBWOOFERS under the rear seat. I hate them so much.
I'm in Tucson at the base of Mt Lemmon on 1.5 acres, so the little bastards are everywhere. The hood open thing didn't work. I'll try the LED.
One time, the little devil chewed through a grommet, entered the cab and ate MY SEATBELT, then made a nest with the material in MY SUBWOOFERS under the rear seat. I hate them so much.
Ha! I used to live very close to you - near Tanque Verde and Houghton. I still visit now and then. Before that, we lived near Sabino Canyon and the packrats were all over the place there.
DO give the LED solution a try. I've installed them on friends vehicles and they've had no further problems.
ishootstuff
Off subject, but what did you do with the Expy you repaired?
Just sold it 3 days ago. I liked it for hauling people around, but it wasn't great off road and certainly doesn't tow like the V10 F150. I'm looking to replace it with a Limousine which will hold more people, get better mileage and be more cool and comfy.
