Worst Automotive Parts / Components of All Time: GM HEI Ignition Module

A new take on the series, highlighting the best and worst of various components. In this episode, learn more about the GM HEI ignition module used on vehicles from the mid 70s - mid 90s.

[spikeprotien]

I remember the GM HEI the coil could put out 50k volts. When the plug wires would go bad and create an open circuit the spark would usually jump through the rotor and ground to the centrifugal weights, you could tell from the rust on them. Of course every now and then the current would hit the module. Game over. Thanks for covering this!

[stoneylonesome]

This is a very good series idea. A lot of people talk about engines and transmissions, not so much about individual commonly shared components.

[richardcumber]

The rest of the known automotive world installs an HEI and makes an oil pump primer out of the old points distributor.

[jimpalmer]

I've owned a couple of HEI equipped vehicles. A 1975 GMC w/ 454 and a 1981 Eldorado. I had the truck for 15 years and never had a problem with the module. The Eldo was blowing one about every month. A close examination of the factory wiring showed a ground that was missing on the car. There was a thin metal strap in the distributor cap that was missing. Once the ground was restored it never blew another module, but it did blow a couple of transmissions. That is another story.

[johntierno]

New to your channel by the way and enjoying. I did 17 years as a GM dealership mechanic and the biggest component failure that I remember was when they went to the plastic intake manifold gaskets on V6 engines that carried coolant through the intake. The 3.1 or 3100 they may have called it and the 4.3 come to mind. This was in the 90's and Dexcool had come out too. These were 100% failure rate for coolant leaks. Coolant would leak externally and internally at the corners of the intake. It wasn't if but when. You would pull off the intake and those plastic gaskets were in pieces. I think the idea itself was as bad as the component. Felpro came out with rubber coated aluminum gaskets that were much more durable. We were paid a flat rate per job and I did so many I was making triple time on the 3100s. You could leave the rear valve cover on then use a line wrench on the rocker arms to open the valve enough to slide out the push rods and change the gaskets

[jayrider]

As a 70's and 80's era GM tech, seems I remember replacing more failed pick up coils than modules. This issue went away when they eliminated the vacuum advance which would flex the wires on the pick up coil to the point of breaking. I still have a collection of GM pick up coil magnets on my tool box...

[tonyscarcare]

Let's do one together on the early GM cable driven window regulators that was my bread and butter throughout the first decade of the 2000s. Grand Am, Alero, Intrigue, LeSabra, and so on.

[njwebste]

I had four Hei modules fail in a month. All standard motor products modules, bought at the local parts shack. I got a Davis module off summit, no problems since.

[markg]

Remember these issues all so well! At our shop we also would see the Ford TFI modules and the 86-92 various GM vehicles with what insiders called "Phantom Stall". On those GM cars we would have to look at the date codes on numerous sensors (crank, cam, MAP/MAF) and replace the ones in question. The worst issue was the intermittent "stall and cranks but won't restart". By the time the car was towed to our shop the car would start right up and could be driven off the tow truck and we were "unable to duplicate the condition". Customers were pissed to say the least. My brother and I wound up doing a series in Motor Age Magazine on how we finally repaired these intermittent problematic cars. Needless to say it took a lot of hours of driving these cars with scan tools and lab scopes connected to various components trying to duplicate the stall condition and catch which electronic sensor was out of range.

[michaelv]

Ford put their ignition module on the distributor in the eighties. There was a class action lawsuit and they had to warrant them to 100 thousand miles. There are companies that sell kits where you can relocate the module to the fender apron.

[johnsalster]

My '88 XJS V12 HE has a GM HEI module located inside the AMP which is mounted on the driver's side intake manifold. That HEI module is, by far, the biggest problem I have w/the car. I always keep an extra AMP and an extra HEI module (along w/tools) in my trunk. I have had modules last for as long as 2 years, while the last two I had both lasted less than 2 hrs. Prices have doubled in the last couple years (although still around $50), but it's really the issue of just shutting down somewhere out on the road that sucks....sure wish I could find an alternative.

[thomaswarner]

I sold/installed lots of ignition modules in the 80's and beyond. Yes the GM modules were quite common but FORD ignition modules were the "big seller" Stories back in the day...like Ford went ahead with manufacturing ignition modules after having over a 54% failure rate in prototype testing... Needless to say, there where broken down, mostly Ford's getting towed in to the shop from all over...

[glennk]

I remember the the first year GM-HEI ignition system back in 1974. If the module failed, the engine will stop. No warning, no engine light. You just simply call a tow truck. The testing unit that was used, was a simple box with a red light, and a green light. Obviously the green light meant good, red, bad. No variance at all.

[paulfrantizek]

The voltage regulators late 70s Fords used were definitely wear items. I recall always keeping a spare.

[cantwell]

I had a 1980 Bonneville Brougham coupe where this issue with the faulty module reared it’s ugly head a few times. I was 17 at the time and had no idea what the issue was. I called my father, told him what was happening. It took him all of 3 seconds to nail down what the problem was. Fond memories now.

[nicholas_scott]

I have a love/hate relationship with the HEI. We use them in old jeeps and IHC trucks. They are great in that they clean up the engine comparments, and get rid of old ignition systems (ie points, prestolite, etc). And generally, maintenance free. .. but I also always carry a spare module with me.

[martyjoseph]

My 76 Nova went out in the mid 80's but I was lucky enough that it only failed when it was cold, once I took it off and warmed it up with a hair dryer and reinstall it the thing would work fine until the car again sat for 8 hours or so. It took me a few days to secure a new one so I got pretty good at pulling things apart.

[Bbbbad]

I found a heat sink, a ribbed piece of aluminum and ground the ribs down for the pin connectors and drilled and tapped the holes for the module to fit. And I polished it up and made sure it was clean bolted it to the radiator cradle near the headlight bucket in a nice breezy place on my 1965 Ford Galaxie 2 dr ht or Fastback as they called it with a FE I have built to tear up the backroads. Close to 500 hp. I tuned a Duraspark distributor for the best curve. And on that heat sink I put a circle track legal Mallory 4 pin HEI module on the advice of a neighbor who runs a class car. I made the loom with the spades and it all worked great. I also found a heat sink from a 351W powered 96 F150 that had been wrecked made for a remote mounted TFI coil. It had a Fomoco coil on it, so I mounted it in an area that also received a nice breeze. I also put a Ford Racing Solid State Voltage Regulator and attached my mix of components to receive a steady 14.3 V, along with the RFI condenser on the coil. No ballast needed. A straight shot of 14.3 running to a Bosch relay triggered by the ignition switch to take a huge load off of the headlight switch. I built this system in 2004, and it fires right up, I use a buss bar from the battery to feed my relays and trigger wires from the solenoid or fused wires from the ignition switch. It has never broken down despite my spirited driving, top speed 154mph and 7000 rpm’s repeatedly. The modern Motorcraft equivalent of BF32s and 9 mm wires. The spark is fantastic. Two of the most cursed pieces of ignition and never replaced since built. The key is the goop and a cool heat sink mounted properly and a breeze to keep them cool.😂

[drf-]

The GM HEI module is not problematic. I worked as a tech in the 80s and 90s. Most GM ignition problems are due the pick up coil, oil wicking up the distributor shaft or a missing ground for the coil. The factory module pictured rarely gives trouble in my experience. Ford's Duraspark is really horrible though.

[apachebill]

The HEI module in my Pontiac is from 1989. Installed with a good heat sink compound on the back. Works perfect. No spark scatter below 6500 RPM. It’s 34 years old.