Why am I going through Ignition modules?

[Nickelcharlie]

Had to replace my ignition module again in my 86 305 GMC pickup. Why do these go out? I have a friend that owns his own shop and he said when he had a truck like mine he was always replaceing his IM.
I replaced the original distributor and it still does it. I thought I had it fixed by cleaning the contacts on the wires going into the cap but after about a year this ignition module gave it up. These modules are AC Delco! I have had them go out going down the highway and in town driving. This one went out after it started!
Any suggestions how to stop burning these up?

[abig84]

had a old k5 blazer that did the same thing. after the second time i just kept a few in the glove box and the tools to change it on the side of the road. i eventually figured out that one of the coil wires on the top of HEI set up was barely stripped and was arching off to ground and that was causing them to blow, cant believe it took me that long to figure it out. so basically take off the plastic cover on the top of the distributor cap and start the truck and see if you see any arching

also check your tach output too, if its hooked up make sure its not grounding out either

ive had square bodies since 1998ish and due to one of those IM going out on me on the highway its the one and only time ive had to have one on a tow truck as i didnt want to fix it on the side of the highway

[1968k20]

I got a non-coil type of cap from Summit Racing and mounted a coil on the intake manifold. I guess the in-cap type of coils get hot and burn up the ignition modules

[Nickelcharlie]

Thank you, abig84 and 1968k20. I'll check the wiring. 1968k20 would you tell me more on the external coil? How did you wire the coil? Did you take out the module in the distributor? I would like to go this route? Thanks again both of you.

[Warrens69GMC]

Stock coil or aftermarket hi-capacity coil?

[cadillac_al]

I have a yard full of Chevys and haven't had a module failure in 10 years. They do fail once in a blue moon but not every year. Even my Skip White distributors are running the original modules. Are you using the heat sink goop under them?

[Nickelcharlie]

Yes cadillac_al, I am using the white heat sink goop. Thanks

[abig84]

Originally Posted by cadillac_al

I have a yard full of Chevys and haven't had a module failure in 10 years. They do fail once in a blue moon but not every year. Even my Skip White distributors are running the original modules. Are you using the heat sink goop under them?

yeah same here since i figured out that arching problem. 3 trucks and im guessing about 12 years later never had one fail. and i think im still using the same distributor from the first truck as everything usually gets transferred from truck to truck as the bodies just tend to rust away for me

but for good measures i still have one in the glove box

[D13]

You do need the heat sink compound.
If you can find them Delco modules have better internal buffering against electrical shock.
Plug or coil wires that are 'marginal' will 'shock' the module. And aftermarket does not mean good. Worse set I ever has was a set of Accel wires. One bad, would still fire but would pop a module every now and then. Particularly cut-to-length if the ends were not cut and crimped with he correct tool. I now run GM wires whenever I can.

[v30crewcab]

make sure you have a good ground between the battery and motor, and motor to body, and motor to frame also.

[kwmech]

You are probably missing the ground strap that either sits under the coil or the wire that screws to a post on the coil. The other end of the ground goes into the center of the 3 wire plug from the base of the distributor. This is what grounds the coil. With this missing it will blow the module all the time

[Nickelcharlie]

Thank you guys, I spent some time this afternoon cleaning ground wires. Thanks for all the good suggestions!

[1968k20]

When I had that problem, I put new ground wires from the engine to the frame. Then I purchased a blaster 2 coil and an he I dust cover. Removes the coil from the cap and away from the module. I purchased this through Summit Racing.

[Pontiac1976]

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Join Date: Apr 2012
Location: Chatt Tn
Posts: 477

Re: Why am I going through Ignition modules?

v30crewcab :make sure you have a good ground between the battery and motor, and motor to body, and motor to frame also.

I Agree grounds, and make sure the screws holding the module clean to the distributor base. I all was put one extra ground strap from body to frame & motor body, cab to frame. Never hurts extra good grounds.