I have a Buick HEI in my 68 LeSabre 350 that is giving me no spark. Trouble shooting using the info on "itstillruns.com" tells me the coil is suspect: A no-spark condition is checked by checking the distributor for power at the connector on the side of the cap. If there is power, disconnect the electrical connector and remove the cap. Check the rotor and the cap for excessive wear. Check the coil tower for excessive wear. Remove the top plastic cap on the distributor cap. Use an ohmmeter and check the coil positive terminal to the metal case of the coil. The reading should be infinity. Check the coil tower and the negative terminal. The reading should be 900 ohms. Check the positive terminal to the negative terminal. The reading should be around 700 ohms. If any of these tests show drastically different readings, the coil is bad. If the coil is good, the cap and rotor are not cracked or worn significantly and there is no spark at any wire, replace the ignition module. My question is: is there a better replacement coil out there? or should I just go stock?
https://www.rockauto.com/en/catalog...455cid+v8,1430019,ignition,ignition+coil,7060 Don’t buy chrap (I misspelled cheap but chrap works!) and don’t buy bazillion volt whizbang either. Get as close to OE as possible. If you’re not sure it’s the coil, try a junkyard unit or ask someone on here (parts wanted) to send you a known good used one. Patrick
You need to also check the pick up coil, If I recall correctly, resistance should be 900-1400 ohms. When checking the pu coil, apply vacuum to the vacuum advance. The wires often break because they flex as the vacuum advance moves. Give both wires a tug where they attach to the pick up coil. If they break or are broken, there's your problem.And, as stated above, I would trust a good used coil over any replacement coil on the market.
When I was running an HEI, I used the MSD stuff. I second checking the pick up. They will give you an intermittent no spark when they go bad from wire flex. https://www.jegs.com/p/MSD-Ignition/MSD-HEAT-Digital-HEI-Module-Coil/757483/10002/-1
Mine died on me the other day and it was the Ignition Control Module. I ordered a two so I can carry a spare with me.
The diagnosis procedure you've been given is horse-shiit. It is OUTRIGHT WRONG in some specs, and frightfully incomplete. https://www.chevelles.com/techref/ftecref5.html There's a million brands of aftermarket replacement coils. Most of them are bottom-feeder Communist Chinese junk. If in doubt, get a GENUINE GM USA coil from a salvage yard.
Wow - that's a lot of good info - thanks Schurkey! I did get BOTH of the readings in the second test, part 1 and part 2 as infinite(OL), indicating an open circuit on BOTH Part 1 and Part 2, so replace coil.
Uhh, with all due respect, Bill wants to know what time it is, not how to build the clock.. There are much easier ways to quickly and professionally diagnose HEI problems, and a “big” soldering gun is not part of that. Like I’ve said before when that link is shown, the last thing you want to be doing is testing like a “club”. You want to be a surgeon.
Key on, engine off, test light should illuminate brightly. This tells you that there is power to the coil, and the primary circuit through the coil is good. Install a spark plug tester on 1 spark plug wire, spark plug end. Engine cranking, test light should flash rhythmically. This will tell you that the coil is being triggered, therefore the pick-up coil and ignition module are OK. Note if spark is occurring @ the spark plug tester. If yes, then pick-up coil, module, ignition coil and 1 spark plug wire are OK. If the test light flashes but there is no spark, then there is a problem with the ignition coil, distributor cap, rotor or spark plug wire. For a “no-start” situation, one faulty spark plug wire will not prevent an engine from starting. If the test light does not illuminate brightly KOEO, then there is no power to the coil B+ or the coil is faulty. If the test light illuminates brightly but does not flash when cranking the engine, then the pick-up coil or ignition module are faulty. At this point, you can remove the distributor cap and rotor and inspect the 2 wires from the pick-up coil to the ignition module. They were known to break over time from the vacuum advance unit working. If they are not broken, carefully unplug the connector to the ignition module, and using a DVOM check AC voltage that the pick-up generates while cranking the engine. You want to see at least .5v AC while cranking. If not, replace the pick-up coil. If so, replace the ignition module. Back when these ignition systems were on everyday driver’s, if the pick-up coil was faulty, then I would replace it and the ignition module as a pair. Depending on the mileage of the vehicle, and the overall condition of the cap, rotor, wires and spark plugs, they may get replaced at the same time too. Very rarely did OEM HEI ignition coils go bad, so they would get transferred to the new distributor cap or reused if the cap wasn’t replaced. If there was a repeat failure of an ignition module (OE or quality brand-name), then the pick-up coil would get replaced too.
So far, so good. "...but does not flash..." While anything can happen, a pickup coil failure doesn't generally cause a module failure. An ignition coil failure can and does cause module failure. If the primary windings of the ignition coil short, the current demand of the coil increases beyond what the ignition module is rated for. The module dies a hot, overloaded death. In my garage, module failures automatically invoke a test of the ignition coil. Ignition coil failures generate a test of the module. Some folks replace ignition coils and modules as a pair.
Yes on the “not” missing... edited.. On GM HEI, the #1 cause by far of no spark was a faulty ignition module. The failure was almost always due to heat. I don’t ever recall replacing an ignition coil for a repeat failure of an ignition module. Yes on the pick-up coil. Your experience is obviously different, which is fine. I worked at a shop during that era, and one of the owners was the head driveability expert and was calling the shots. He was right most of the time! Good mentor. Back in the 80’s, we were at a driveability class at the local vo-tech facility. There was a GM engine on a dyno that had HEI ignition. The instructor had the big Sun ignition analyzer hooked up, and we were going over raster patterns, firing lines, all the stuff that an old oscilloscope would show. My boss didn’t like the firing KV or something and he let the instructor know. “It’s fine”, said the instructor. My boss wouldn’t let it go, and he said there was a problem “under the cap”. No, no it’s fine. When break came, he told me to find a screwdriver and get the cap off. And that I did, and the rotor was burned up so bad it was surprising that the engine ran. The instructor was red in the face. My boss (gruff old guy), not one to gloat, said something like “next time when I talk, you might want to listen” lol. Ford TFI was another one that had problems with ignition modules mounted on the side of the distributor. Same thing there - repeat failures got a pick-up coil. Ford knew it was a heat problem, and eventually moved the ignition module off of the distributor housing. If an engine had ignition coils mounted directly onto an ignition module (wasted-spark GM for example), any hiccup and the coil pack (or individual coils) and ignition module were replaced together.
Dave Ray converts the stock distributors to MSD trigger only, or GM HEI. His GM HEI conversion mounts the module to the bottom outside of the distributor, or as a remote mount on a heat sink. You also use the stock type remote mount coil. Along with custom curving of the advance and full rebuilding of the distributor, a much better option than using a junkyard OEM Big cap HEI. www.davessmallbodyheis.com
Well Cr*p - I received my new DUI coil (it got good reviews) and just for giggles I put the digital multi-meter on it - same results. What the? So I dug out my high school Micronta meter - good results - ON BOTH the new and old coil. My digital meter was not reading low enough on the ohms! It does not have a "low" scale but is supposed to read down to 1 ohm. It pays to have good tools! More troubleshooting! BTW this is what I checked(coil is out): To test the resistance of the coil, touch the positive lead to the red wire terminal and the negative lead to the yellow/white wire terminal. The primary resistance value should be 0.6 – 1.5 ohms. To check the secondary resistance, touch the negative meter lead to the ring terminal on the black wire and touch the positive lead to the bottom of the coil where the rotor bushing makes contact. Your secondary reading should be 6.0k – 10k ohms.
