Lost an ignition module. Why?

[Old60Driver]

So, I got the headers installed and welded out. AWESOME!

Lost an ignition module on the way home from the exhaust shop. Super NOT awesome.

I checked voltage at the dizzy. All good. I thought it was the coil. It was hot. And when I say hot, like the surface of the sun hot. I figured it had shorted, and replaced it (I had an extra in the truck), but no dice. Had to pay a tow to get her home. I had a known good ignition module in the garage parts bin, and that did the trick.

Here's my question. WHY did it fail? The only thing I've done ignition wise, was to replace a spark plug due to heavy deposits that I noticed during the header install. For the record, it was an AutoLite.

I've never ohmed out my aftermarket wires. Could that have done it? Or maybe the system hated the AutoLite plug?

Oh, and for the record, the distributor was a 65 dollar Amazon special, if that makes a difference...

Thanks in advance. Gonna go grab a gin and tonic. That was a long time on the side of the highway in south Texas heat!

 

[dusterdude]

It happens,nothing you can do about it.

 

[Dave M]

Did the exhaust shop do any welding on your truck?

 

[Old60Driver]

Did the exhaust shop do any welding on your truck?

Actually, they did. Drove for another 45 minutes after, if that makes a difference?

 

[mtnmankev]

Just make sure when you replace it, apply a healthy coating of white heat sink compound on the metal section where it contacts the dizzy.
Don't install dry, or coat with anything else.

 

[Ellie Niner]

Just make sure when you replace it, apply a healthy coating of white heat sink compound on the metal section where it contacts the dizzy.
Don't install dry, or coat with anything else.

Yes! Was just gonna say this...

 

[Old60Driver]

Didn't have any compound, but the old one I put on had some. I know it's not the best, but it's what I had for the moment for troubleshooting. I'll grab some and apply it before I run her again.

That being said, she fired up, so I know that it was the module, but she seems....sluggish? Also, she tried to die on me while I was test driving her. I have to admit, I'm not HEI expert. Can modules/new coils be weak? Can the plugs short out a system? How much damage can a badly grounded weld make to the ignition system?

Sorry for all the questions. Want to take my wife on a cruise tomorrow night before I leave for out of state work.

Thanks in advance y'all!

 

[Goldie Driver]

My original died after 40 years - replaced it with a made in USA BWD one.

It made around 6 months.

I had a shop check it out for the same concerns you have.

Their answer?

Bad luck, and they prefer OE parts.

So, AC Delco under the hood and I bought a spare one for the glove box.

It, sadly, can happen.

 

[mtnmankev]

Heat is the biggest enemy of the modules.
Without adequate heat sink compound, a module will heat up very quickly, and could fail or work less than 100%.

 

[Old60Driver]

'Preciate all the comments folks. Looks like I'm in the market for new ignition module(s). I too, believe in spares. lol

As I mentioned, purchased an Amazon special, found here. Turns out a few other folks have had the same problem I did. lol

If I replace the guts inside (coil, module) with quality ACDelco stuff, is that sufficient insurance, or should the whole dizzy be changed?

 

[mtnmankev]

I don't see the need to replace anything other than the module if that restores the operation.
But, while you have it open, check the mechanical advance weights for worn pivot bushings, weak springs, or dirt/rust that can cause them to stick.

 

[Old60Driver]

Okay, so I've got a new ACDelco ignition module on the way. Until then, I thought I'd check the timing.

I disconnected vacuum advance, set it to 12 degrees. Good baseline, and she seemed to like it.

Here's my concern: When I reconnect port vacuum, I'm seeing an increase of 18 degrees at 800 RPM, for a total of 30 degrees....

That can't be right, can it?

 

[AuroraGirl]

Okay, so I've got a new ACDelco ignition module on the way. Until then, I thought I'd check the timing.

I disconnected vacuum advance, set it to 12 degrees. Good baseline, and she seemed to like it.

Here's my concern: When I reconnect port vacuum, I'm seeing an increase of 18 degrees at 800 RPM, for a total of 30 degrees....

That can't be right, can it?

Did you listen to mtnman and verify your weights are good?

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heres two SBC distributors with clean weights

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here are some that are NOT good
The 2nd photo was my distributor, they would cause the idle to stick at like 1300 or so periodically and made it a confusing mess to have proper idle and etc etc

 

[AuroraGirl]

if you want a working OE coil I have a few that are unknown mileage but they arent bad looking by any means

 

[Old60Driver]

if you want a working OE coil I have a few that are unknown mileage but they arent bad looking by any means

Thanks, but I have a back up ACDelco unit that I have laying around.

Also, regarding the weights, they looked in perfect condition. No rust, good springs, etc...

Thanks!