Hello Forum,

Seeking helpful advice from anyone knowledgeable with HEI systems.
Last weekend, my 1980 L-48 4-speed vette died during a short 20-minute drive. Research indicates it’s probably an issue within the HEI ignition system (details below for anyone interested).

After reading several past posts regarding HEI issues, I am left with a few questions:

• Are there ways to test or verify coil function?
• Are there ways to test or verify command module function?
• Which brand coil and or module have you bought in the last year?
• Where did you purchase from, and would you purchase that brand from that vendor again?

Yes, I’m aware most of everything available is crappy Chinese quality (We all know the situation, so no need to re-state it.)
My hope is someone will post brand and vendor info for HEI components purchased that worked as expected.
No, I am not wanting to replace or upgrade the entire system. Simply looking to restore functionality with whatever reliability possible.

Thank you in advance for any helpful feedback.

For those who want more detail (the rest of the story):
This is the first reliability issued experienced in the three years I’ve owned this vette. Therefore, my focus has been on suspension, steering, and brakes (with some minor effort on comfort along the way).
Aside from having the EGR emissions system removed, I consider the car to be "stock" because the block, heads, manifold, exhaust, are all correct for the year. However, a few bubba-mods have been identified during my time with it. I am not a mechanic. Do consider myself to be decent at researching, testing, and turning wrenches.

This drive consisted of 3 miles neighborhood driving (under 45 mph) up to a drive through line. Approximately 5 minutes in line. Then one mile into the return trip, as I accelerated away from a stop sign (not aggressively), the engine sputtered. Quickly pressed the clutch and tried the throttle but it died almost instantly. On the side of the road, I removed the air cleaner cover and cranked. It cranked like usual, but there were no hints of firing. Called the wife who showed up in about 15 minutes. With her cranking it, I could see fuel spraying in the carb. Lead me to suspect ignition. Had it towed home (thanks to wife for signing us up for AAA).

I've lurked on the forum for years so I've read 1000s of posts and remembered ignition woes being common and not easily diagnosed. Admittedly ignition is not my strong suit, so I searched and re-read anything that seemed pertinent. Pretty quickly suspected I might have the dreaded heat related - intermittent coil or control module situation.

I don’t have a proper spark tester (yet), so my timing light is my best option for verifying spark (I realize it won’t confirm strength, just existence). Cranked it over and the car started almost instantly (FYI This is about 3 hours after the initial issue). Didn’t run as smoothly as normal, but it would idle. The timing light flashed, but it was very erratic. Some flashes were doubles. Others were separated by odd gaps. Aimed it at the crank pully and the TDC mark appeared to jump all around. Didn’t know how to isolate anything for more testing so I shut it off.

After reading a few more HEI threads, I pulled the cap, rotor, and module to inspect for any issues mentioned. Everything was dry and clean with no odd smells or obvious signs of issues. The cap and rotor are too clean to be original. Their terminals have some carbon, but nothing overly concerning to my inexperienced eye. The coil, module and other internals all appear to be original but do not show any signs of burn or overheating and neither has a burnt odor.

I did not see any posts with specs or techniques for testing the coil or the command module. Apparently most people go into parts swap mode guessing at the issue. Modules seem to be more failure prone, and many owners mentioned carrying a spare. My plan is buy new parts based feedback received, but this also gives me a reason to explore the local salvage yards too. Few still have cars of this era so my hopes aren’t high.
Thanks again!

 

My first move would be the module. See if Borg Warner still offers them ( NAPA). It started once it cooled leading me to a heat soak issue with the module. It fired so the coil is making spark. Back when HEIs were the norm, module failure were no overly common but were the usual suspect.

 

If i had to replace a coil i would try NGK.
looks like cap and rotor would not be a waste of money.
the module i bought back up nos ebay, but assume store bought would at least fire? Make sure paste used..

but before anything i would try this below to confirm

 

Can the coil be tested, yes. Can the winding the module is connected to be tested, yes. Can the module be tested. Not that I am aware of.
Best source for parts , Davis unified ignitions in Tennessee. USA made quality parts.

 

The Distributor Cap and Rotor in the pictures are sure worn past their prime. It is time to get some new parts for your Corvette!

The only real problem I had with my HEI in the 1988 C4 was an "intermittent miss" that would not go away until I saw that the power clip that supplied power to the HEI had been broken and the wire was loose and was moving under hard acceleration. Intermittent POWER will make all sorts of problems and could zap the module if you are not lucky. Verify the supply of 12 volt power to the HEI unit.

I have but one HEI and for that I have a spare Module, Distributor Cap, Rotor, Ignition coil and Pick-up for the HEI. This was to allow me to use the C4 more comfortably knowing the issues with the HEI and that I had the spare parts.

For my MSD Distributor I don't need any spares. I do keep the spare pick-up sensor for some reason. My MSD ignition system on the C3 is wonderful and makes a very HOT Spark! I love the sound of the coil firing multiple hits at low speeds, it sounds like a welder. It is fairly straight forward to work on and far better than any HEI system I have had experience with.

 

Maybe a long shot, and I know maybe less than you, but the yellow wire looks to maybe be pushed out/not seated/snapped into it’s retaining clip. May not be properly mated with it’s male counter. I would push it in, along with inspecting all other wiring for proper seat and their sleeving for chafing, which would cause arching and sparking. Had a similar issue on a ‘68 Firebird, so only talking about lessons learned on that one.

 

I agree DUI for parts. I bypassed my module entirely and use my MSD 6.AL to trigger the spark . It works very well.

 

From my experience when the ignition dies completely it's been the pick up coil not the ignition coil. The pickup coil connects to the module and rotates when the distributor advances. This movement can lead to a wire breaking over time.

The pickup coil can be tested with an ohm meter. If it fails the test you have to remove the distributor as it sits under the advance weights arm. Knock out the pin holding the gear and the distributor shaft will then come out allowing access to the coil.

 

Thank you all for the info and feedback.

I received a private message with a link to a YouTube video with specs for testing the coil and other info Somehow I forgot to search YT for info before but now I have. The additional research adds to my belief the module is my main problem but the feedback on my cap & rotor has them on the list of needs too.

Curious if anyone has experienced issues with the magnetic pickup coil?

Bob3700 Looked into the components Napa offers, and Borg Warner is not listed. However, they do have Delphi and AC Delco which I will keep in mind.

4-vettes I like the Performance Distributers products. If I knew I wanted to keep the motor, I'd consider a complete replacement distributor. For now I'm going to call them about components which seem to be priced similar to name brands on several sites.

litevette Appreciate your note on the questionable wire. One of the YT videos I watched illustrated a common wire issues. So, I will definitely double check all the connections and wires when I put it all back together!

By the way, I picked up an inline spark tester today.

Looks like it's gonna take a few days to get parts. I will update once I make progress.

 

I just got my MSD Ultra 6Al Friday. where did you run the red and black wires for battery and ground? I read some run them to the starter, some to alternator since battery is in the rear.

 

I will need to see what wires I ran to the pick up. I don't know if the 6AL ultra has a different wiring diagram though.
What I ended up with is a poor man's crank trigger, but so far it works well.

 

Ok green and purple go to the pick up on mine.

 

happen to me on the highway just died out of nowhere . Made it to the shoulder waited about 20 minutes and it fired up and got home ..all looked good but I replaced the distributor, module and rotor about 100 bucks . Problem solved. I used ac delco parts no problems I’m about a year

 

Did you discover it was the ignition module? I had this failure 3 or 4 times in less than 8000 miles with replacements from the local auto store. They are mostly garbage. Then I found a NOS delco module and picked up a spare to carry and havent had an issue in the last few years since. My money is on that or the condensor and you might want to fix the white (yellow) wires terminal connector. its supposed to be pushed into the plastic plug like the green.

 

Just a last-minute note.
In the photos, note the one with the coil exposed, dust cover is off.
Note that the coil has 4 hold-down bolts.
Note that on one corner has a BLACK GRD wire.

Make sure that the wire eyelet, bolt and more importantly the coil corner is clean of paint. That bolt threads into plastic so it is not a good GRD.
The bolt head contacting the coil is the actual GRD.
Scratch / sand off some of that coating on the coil for an excellent GRD.

 

Thank you for the note on that detail HeadsU.P.!.

 

Parts arrived this week and I've finally carved out some time to work on it. Cleaning and addressing some minor "while I can" issues around the distributor before I assemble.

Follow up question about the vacuum advance system: How quickly should it bleed down? When I use my manual hand vac the actuator functions smoothly and without any obvious issue. With a four or five "pumps" the movement hits its limit with pressure at 15 on the gauge. However, the pressure bleads down to 0 within 2.5 - 3 seconds allowing the mechanism to reset to normal as well. Doe this sound correct??.

 

As I recall, all the Vac Cans will do something like that.
It's irrelevant because the engine provides constant uninterrupted vacuum supply while running.

 

The leak down sounds fine. The 15 inches of vacuum sounds like a vac can for a engine with a factory cam.