Hey everyone.  I have been MIA for several years, but I'm baaack!  Still have the same car that's in my sig - 23 years this month!

About the car....  Took it on a drive several days ago.  Ambient temp was in the low/mid 80s.  Coming back into my neighborhood it starts cutting out bad.  Tach would go to zero and then spring back, so I know something is going on primary side of ignition.  Luckily it was all downhill to my house so I could coast, but my driveway is a steep up.  Got it up to the top, but couldn't get it into my shop where it lives.  Had to let it cool down for an hour and then I could get it in the shop, but it was still cutting out pretty bad.  Haven't driven it since, but tonight I started it up and it was running great with no noticeable miss or cut out. 

Stuff I've done so far - 

• jiggled ignition key when it was cutting out, no change
• jiggled primary wire to dist cap when it was cutting out, no change
• tonight when running (cold start) checked voltage at primary wire to dist cap - steady 14+ volts
• took the cap off and removed coil.  tested primary side of coil: .8-.9 ohms.  tested secondary side: approx 6K ohms.  
• visual inspection of cap, rotor, coil, module, etc.  All looked fine visually.  
• Next step will be to take the mech advance off and take a look at the pickup coil.  

Do these symptoms point to anything definitive?  I'm thinking coil, even though it passed it's resistance tests, since I know they can be just fine until hot.  But also could be pickup coil or module?  

 

I'll take "Ignition Modules" for $100, Alex.....

Joel Adams
C3VR Lifetime Member #56    
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

Hello, For those who attended the Mystic Gathering, you will remember that Adam's 79 had the same symptoms. We changed the internals in the parking lot, and all was good again. It appeared to be the contact between the spring loaded post that contacts the coil. Burned bad. 

Click on image for full view

AC Delco ignition module for the win!

I had to replace two aftermarket units within months until I found an AC Delco.  It’s been flawless for 10 years+

Yep, ordering a Delco now.  I was considering a Walker at half the cost, but your comment seals the deal.  I think the old unit may have been a parts store brand - "Select" - can't even find it on the interweb.  

thanks to all who commented.  I was pretty sure it was the coil, but great to have extra assurance.  

 

It's a bit bizarre that there has been a little spate of this sort of problem recently - I had the same thing last June - that turned out to be the coil - and I seem to recall at least one other on C3VR having a similar issue.   The GM distributors must be ab le to talk to each other and coordinate their "vacations"!😄

I might have to go to the $200 clue on this one....  new Delco coil did not solve the problem.  Drove it around the neighborhood for 10 min so I could limp it home if need be.  Passed that test, but failed the longer test drive.  Exact same symptoms: it'll run, but will continuously cut-out for 1/2 to 1 second.  Hold it at 2k rpm, and tach will immediately go to zero then bounce back.  It'll idle for a few seconds, but will die when it cuts out.  It's parked in a semi safe spot so I'm hoping it'll cool down enough in a couple hours that I can limp it home to do some diagnostics.  

What's the next best guess, can it be the module?  I know they typically fail completely, but I'm not seeing much else it can be unless it's the pickup coil?  I know those wires flex a lot so I'll take a look at that when I get it home.  But I know that unit is not that old and has very few miles on it, so it'd be strange for it to be bad again.  

 

It sounds like the ignition module is your next purchase😄   I think they are susceptible to overheating, and I believe that's why the grease underneath is so important when fitting the new one.👍

Yep, new Delphi module seems to have solved the problem!  Replaced it yesterday, and then Drove it further than after replacing coil - no issues.  I made sure to put a liberal coating of di-electric under the module and on the hold down screws.  I did a little research last night - I've had that same module in there for 12+ years, so not feeling too bad about it going.  

 

Glad the problem is fixed!  But not sure I wanted to here the time you've had the module though😄 - when I put the new coil in ours I decided against fitting the module I'd bought because the connecter was extremely fragile!   As far as I know, it's the original item - with the best part of 137k miles on it!😱

I'd replace everything in the dist that's original.  On one side of the module you have this wiring harness/connector/radio noise capacitor:
https://www.amazon.com/dp/B00557RQ46?psc=1&ref=ppx_yo2ov_dt_b_product_details

I replaced this along with my module.  And the one I replaced wasn't original, either.  I mostly replaced it since the tabs on the connector that plugs into the dist cap were missing.  

On the other side of the module you have the connector for the pickup coil.  

https://www.rockauto.com/en/moreinfo.php?pk=49743&cc=1041040&pt=7176&jsn=939

(I usually go with delco if I can, but I wasn't seeing that option on Amazon or RockAuto).  If this is original to the car, I would definitely replace it - or just go with a whole new distributor.  The wires on this guy have to flex when the vacuum advance operates; they are probably very brittle and ready to disintegrate if original.  But unfortunately it's not an easy fix to replace the pickup.  Remove the dist from the car, and then remove the shaft from the body.  It's pretty much a whole rebuild.  When mine failed years ago I bought an el cheapo HEI knockoff and ran that for years.  But I have since rebuilt my original distributor and use that now.  

 

Just a thought Dave: The ribbon connector on the lower steering column. Have you played with that in an effort to see if it effects the problem?

Tilt or standard steering column? 

Steve 

Love that metallic red.  Cheers.

Hi Steve, thanks.  Good thought.  It's a tilt/tele column.  AND....I very recently replaced my turn signal switch, which of course involves also replacing that ribbon connector.  BUT.... I was able to back probe the red primary wire to the distributor cap when it was cutting out, and I could see that there was a constant 14 volts on that wire even while it was cutting out.  And the new ignition module seems to have solved the problem.  But yes, diagnosing an ignition cut out on a 50 YO car, you would definitely want to make sure the ignition is getting constant steady power.