HEI Ignition Control Modules Keep Failing- Any Ideas?

[5Tractorguy]

About to replace the 5th (I think) ICM in my 1-ton tomorrow. Ever since I rebuilt and installed another engine last November, I've had nothing but ignition problems.

Any ideas as to why the modules would keep failing?

- I started with a new SKP distributor from Rockauto upon the rebuild. Ran well but the advance wasn't working properly... ordered another dist.

- Bought another dist from Summit (part# SUM-850001R) which gets mixed reviews, but gave it a whirl. Worked for a short duration then developed a misfire.

- I began swapping components and new ICM's between these distributors to make one, but the misfire was still prominent no matter what.

- Found an old HEI dist I had kicking around here with 100% OEM old GM electronic components. Cleaned it up and replaced the cap/rotor with a new MSD. Ran great for about 3 months! Then this past week the truck started shutting off sometimes when I came to a stop (thought it may be carb/fuel). Then it just shut off while driving like someone turned the key and wouldn't restart.

- Replaced the ICM- back in business. Made it about 10miles today, came to a stop, truck died, won't restart.

I've been through 3 different distributors, with various OEM parts, aftermarket parts, 3 different cap and rotor sets.

All I can think of is a bad ground in the wiring harness or something is back-feeding into the distributor but that's just grasping at straws. Anyone else have an issue like this before?

Picked up another new module on the way home tonight (truck is beached a couple towns over). Going to swap it out again tomorrow and hope that it makes the entire trip home this time.

[kwmech]

Is the center ground strap in the cap?

[400/400]

Issues like this can be very frustrating.

Powers and grounds.

Is your HEI getting consistent full battery voltage? Good wiring and ignition switch?

All ground wires/ straps clean? Ground side, If I recall, the module has a ground through one of the mounting bolts. Is the intake painted? Distributor body gets grounded through the hold down clamp. If paint is too thick on clamp or intake and it didn’t scratch through, there could be a ground issue.

Also heat is an issue for the module. Need to use heat sink paste between the module and distributor. OEM was a heavy white paste. Often people say to use dielectric grease. I don’t know if it conducts as well as needed for the heat transfer. I have used aluminum anti-seize with good luck.

It sounds like yours is failing more quickly than a heat issue would cause. Makes me wonder if it isn’t a wiring issue. How is the pin fit? Perhaps it’s just loose enough that when initially installed it works and wiggles loose overtime looking like a failure. If you wiggle the wires while running, does it stall?

[Dead Parrot]

Your stop, restart, stop issues sound like what happened with my C10 decades ago when my dad still owned it. It turned out to be a loose wire somewhere. Too many years ago so I don't remember where the fault was. But it WAS an electrical issue, not a distributor issue.

If it is a loose or corroded connection, possible your swapping distributors is wiggling the wire enough so it makes a temporary connection. Might be worth checking the ignition switch at the base of the steering column. Plus the neutral safety switch. If either/both are bad or out of adjustment, could cause an intermittent running issue.

Since you swapped engines, double check the wires on the starter solenoid.

[KQQL IT]

Our hei failure.
Didn't eat module's but ran like doodoo

[Just call me Sean]

You don't use dielectric grease on the module, you use thermal paste.

[hatzie]

I use Dow Corning 340 thermally conductive compound on the 6.5L PMD and stuff like the HEI modules that need heatsink compound.
SuperLube Heat Sink Compound is more available and will work quite well between the HEI Ignition module and the distributor casting.

Check the bendy steel coil ground is making good contact with the transformer laminations. If the screws don't snug down tight enough it won't make good contact.
Make sure there's dielectric grease on the silicone disc around the spring & rotor button.

If the module pigtail & condenser harness is crunchy or even mildly loose on the module or cap replace it with a new GM 19207437.
If the hot connection to the distributor cap is not snug and solid replace it. You can buy pigtails but you have to be careful to get decent product. Most use PVC or even THHN house wire instead of decent quality crosslink polyethylene.

If you roll your own use 12ga red SXL jacketed wire.
The connector components are below.

• The HEI Power& Tach shell is Delphi Packard 56 series 8911979. This two position TACH and BAT connector shell holds up better than the single terminal shell.
• The 10-12ga BAT wire terminals are Delphi Packard 56 series Female 12124513.
• The 14-16ga TACH terminals are Delphi Packard 56 series Female 2965511.

The Delphi 12085271 ratcheting crimp tool will crimp these terminals.

[5Tractorguy]

Finally got the truck home this past Saturday.

Changed out the module- still wouldn't start. So I pulled the dist and changed with another I had, swapped over the module and cap/rotor... still nothing.

Decided the pickup coil must've went bad, but thought I'd swap the HEI coil just for kicks first. Tuns out, that was the problem! When I pulled the coil out the yellow wire fell right off. Must have just barely been making contact while driving around.

Still doesn't explain the ignition component failure before this coil and distributor were in the truck, but hey... I'm back on the road again and it's running strong.

Thanks for the replies guys!

[hatzie]

Looks like those wires got pinched between the cover and the distributor cap.