HEI module death symptoms

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kiss

kiss

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I was driving today, pulled the car into the Target parking lot, and the car started sputtering. Kept sputtering/revving up a little/cutting out for a second until it finally shut off.

Tried to start it, ran for a few seconds, sputter, died again

Symptoms seemed like a fuel problem but I watched gas going down the carb/accel pumps worked but it would still die. Must be electrical.

Switched-out the HEI module and it works fine now. Dead module. No big deal, that module has worked a good 8+ years for me and I had a spare.

My question is I'm wondering is this a normal symptom of how HEI modules die? I was under the impression that since it's electronic, if it's dead, it's dead, and doesn't try to run the car in short bursts...
 
It could be the HEI failed, but not in the output transistor. Transistors used in applications like that often fail shorted, but it is often due to open plug wire or some other stress over long time period. The problem could be from two other parts of the circuitry, the part that detects the timing signal from pickup, or the dwell/current control. The other possibility is the HEI was good, but replacing cleaned up a loose connection to ground, or other pin, or even intermittent bulkhead connection issue.

I am curious, so I find the root cause, by further testing or disection. But have been very lucky myself, and for the wife, always able to drive home. My experience comes from helping others, or fixing broke stuff.
 
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I've seen them do that and even stranger things. My father-in-law bought a 64 Rambler that someone put a SB Chevy in and it would idle just fine but as soon as you brought the rpm's up above 1300-1400 it'd start missing on a couple cylinders. Did a complete tune-up and still the same problem. Checked the valve springs and replaced a couple that were a little weak, still same problem. It would still run but just down on power and sputtery (is sputtery a word, lol). Replaced the HEI module and it's been running fine ever since. Wasn't dirty connections either, checked that. Just a bad module
 
Electrical problems are often easily diagnosed with a test plan and proper equipment. Since the problem was repeatable at an RPM above 1300-1400. A timing light with clamp-probe could be used. Spark current triggers the light, lack of spark or weak spark, no trigger. The light flashes will become irregular just as engine operation. An oscilloscope with high voltage probe, used to view the -coil terminal provides more clues, it views the dwell time, continuity of ignition transistor, estimate of peak secondary voltage, and spark duration. It is also possible to view the timing between cylinder events, that with reference signal will indicate particular cylinder problems. If the electrical signals are proper, with the exception of periods in between, then loss of power for particular cylinder, increases the period, so that indicates low compression, leaky valves, worn springs, fuel distribution....
 
Back in the day, Intermittent temperature related failures were more common with Fords modules but could happen with any. Engine just shuts down, so wait about an hour, then fire it up to go some more.
Chryslers modules would sometimes get hot enough to melt the gelcoat from the circuit board, making a mess on the inner fender, before failing.
 
KitCarlson said:
Electrical problems are often easily diagnosed with a test plan and proper equipment. Since the problem was repeatable at an RPM above 1300-1400. A timing light with clamp-probe could be used. Spark current triggers the light, lack of spark or weak spark, no trigger. The light flashes will become irregular just as engine operation. An oscilloscope with high voltage probe, used to view the -coil terminal provides more clues, it views the dwell time, continuity of ignition transistor, estimate of peak secondary voltage, and spark duration. It is also possible to view the timing between cylinder events, that with reference signal will indicate particular cylinder problems. If the electrical signals are proper, with the exception of periods in between, then loss of power for particular cylinder, increases the period, so that indicates low compression, leaky valves, worn springs, fuel distribution....
Click to expand...
I agree but in my case the car needed a tune-up already so I did it first to eliminate any problem there and was hoping it would take care of it. When it didn't I looked elsewhere. Unfortunately not very many people including me have the luxury of owning a oscilloscope to diagnose it that way. It is a very handy tool but I don't have the money for a decent one.
 
Scope prices are not that bad. About $300 will buy a new color lcd, 1Gs, 100 mHz bandwidth, with USB for saving data and interface with PC. Used scopes for $100 well choosen, are a great value too. Scopes are smaller and reliable, compared CRT, units with knobs and switches of the past.
 
Swapping a part does not always prove cause and effect. Amazing what a good ground can fix. Did you have a dedicated ground wire for the HEI module, or just rely on a screw into painted metal? If the later, the act of swapping may have fixed an iffy ground. Just seeing fuel doesn't mean it is the correct flow. Gas engines are very touchy and fire only in a narrow O/F range. If it was fuel related, it may have just gone away temporarily. Many of my fixes don't hold and turns out to be the 3rd or 4th thing I try.
 
BillGrissom said:
Swapping a part does not always prove cause and effect. Amazing what a good ground can fix. Did you have a dedicated ground wire for the HEI module, or just rely on a screw into painted metal? If the later, the act of swapping may have fixed an iffy ground. Just seeing fuel doesn't mean it is the correct flow. Gas engines are very touchy and fire only in a narrow O/F range. If it was fuel related, it may have just gone away temporarily. Many of my fixes don't hold and turns out to be the 3rd or 4th thing I try.
Click to expand...
Dedicated ground to the HEI mounting bolt. In fact about a week or so prior to the incident I added the grounding wire, as it was forgotten when some of the engine wiring was redone.
 
KitCarlson said:
Scope prices are not that bad. About $300 will buy a new color lcd, 1Gs, 100 mHz bandwidth, with USB for saving data and interface with PC. Used scopes for $100 well choosen, are a great value too. Scopes are smaller and reliable, compared CRT, units with knobs and switches of the past.
Click to expand...
They are definitely a lot cheaper than they used to be but when you're disabled an extra $300 doesn't come easy. I haven't ran across any good deals on used ones. Wish I could cause it'd really come in handy with all sorts of things I do. I'm an amateur radio operator and could use it for radio related projects too.
 
A USB scope is less than $150, but they are low BW, typically 20-50 mHz. Also need notebook PC, to be portable.
 
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