One of the hardest things on an Old GM engine with HEI ignition to Diagnose the Ignition Control Module when they go bad. I sat there for a few days scratching my head.

Am I getting fuel did not look like it last Sunday Morning since it was running when I parked on Saturday but every once in awhile would cut out like a Fuel Vapor lock in the lines on the last leg of my 3 hours of driving on Saturday on 92 degree day.

Sunday morning went to fire the car up for another drive nothing not even a sputter so thought maybe Fuel Pump then I checked for fuel after buying a new one last night.

Tonight purchased a HEI Ignition Control module because 30 years later remembered the symptoms of the last one that went out on my 1976 Chevelle I owned back from 1982 until about 1986. They will limp home but once they cool off you get nothing or a faint spark then fill your garage up with unburnt fuel from the faint spark which is what I did last night.

The Ignition Control Module dies in 2 ways either by a Slow Death or a Fast one that leaves you stranded on the side of the road. Both of mine that have died were slow death sputter like Vapor Lock or failing fuel pump than when I attempted fire up the next day after it cooled either got nothing or a few sputters. I knew it was not a fuel pump when I attempted to fire it up again last night and filled my garage ally way up with half burnt fuel and a few sputters from a very weak spark.

Purchased a new Ignition Control Module this evening coated the leads and bottom of it with the Die Electric Grease that came with the Borg Warner Module then held my foot to the floor while it sputtered and spit then fired up. Stumbled for a minute or 2 while it cleared the cylinders of the unburnt fuel then ran like a charm.

 

Glad that's all it was. I always carry an extra one with me in the storage compartment, along with some tools and fuses just in case.

 

Saturday while driving around I stopped at harbor freight in the morning and picked up a tool pouch and to buy some tool drawer organizers for my SAE sockets.

Than after my engine stumbled a few times went to Lowes and got an inexpensive 40 piece tool kit for $9.95 that had a few pliers, screw driver bit set, adjustable wrench and channel locks. Finished filling the tool pouch with common wrenches then put it car.

I know to carry tools in old cars and that was the incentive to do it

 

Umm, isn't that pretty much how every component on a car fails?

 

Yup but figuring out the problem in a short period of time and making the right purchase is where the skills come in. yea I thought fuel pump since I have had them die a slow death before also or even Vapor Lock which when your driving the car stumbles or dies.

Once the engine was cold and really saw the problem after checking fuel system at first thought.

I once read all carburetor problems were 90% ignition system problems so once I looked beyond the obvious than I looked at spark and did not even pull a plug when I saw the half burnt fuel roll out of my exhaust system.

Than knew to buy the Ignition System Control Module which when failing can look like a fuel system problem at first if they die a slow death

 

Good for a rookie to know that fuses, a fuel filter, a couple plugs, a fan belt, a relay, and.......add an ignition module to the cargo tool box.

 

I have overcome many problems since I bought this 1977 Corvette last April 2013 and put some bucks into it. First problem I had with it pulled really hard right so I had all the suspension and steering components rebuilt last summer. It still pulled right until I rotated the tires. Anyone that has worked in a tire/alignment shop knows that after a suspension rebuild the continue pulling at this point is a tire pull from the uneven wear on the tires and once you move them to rear the pull goes away.

Next was the Carb was burning fuel way to rich from others trying to incorrectly tune the a carb leaking with 37 year old gaskets. I rebuilt the car cleaned it up took me a 6 pack of beer and 5 hours to clean the carb then rebuild it.

Than in previous post a week or so a go I sent out how to performance tune the timing on a SMB 350 than readjust the carb with a Vacuum Gauge. You always performing the timing first then readjust your carb. Why because while adjusting carb does not affect timing the readjustment of timing will affect the vacuum in the manifold and change the carb settings so always readjust your carb on the engine after a tune up on these Carbureted engines. I am guessing the performance tune fried my 37 Year Old HEI Ignition Module. My engine only has a little over 46,000 original miles on it for being 37 years that is great. Still has all the original tape on the vacuum lines which I have cut them all back by 1/4 of an inch to reseal them but there has been no need to preplace them yet.

Things I relearned recently since it has been 25+ years since I owned a HEI ignition system and a carburetor.

 

When an HEI engine fails to run as expected (instantaneously), the ignition module would by my FIRST choice to test. Those modules have failed due to heat/time/use since the first day they came on the market. They are reasonably reliable...but an engine compartment is a nasty environment for electronic devices.

As others have mentioned: If you have an HEI system, carry a spare ignition module and a screwdriver with you.

 

Have to agree for most that have Corvettes or any Chevy in the 1970s with HEI. Cure all your problems and when you buy an older car get it running right I have spent the last year of owning it.

If your new at buying an older car change all the fluids in the Transmission, Rearend and Engine. Bleed out the brake system and do not believe anything the previous owner tells you unless you have receipts from that owner.

I changed all the fluids in the first month of ownership then went from there on my 1977 Corvette every thing after that is fixing up the problems others did not perform when they owned it.

 

Had one go bad once going down the highway. Its just cut out and died. First was to check for fuel squirting into carb. That was ok which next was to check for spark. No spark. Bingo! replaced control module and continued on.

 

Yeah, and how many of us haven't had to replace an HEI module. The one positive note is that they are a lot cheaper and simpler to diagnose than all of the EBCM and other modules in the late models.

 

Been working on HEI since before was the points system, brand new.....

I have had TWO sending coils fail, requires taking that dizzy apart to slide the rotor shaft out and get to it, it's the white/green wires going to the HEI modlule....they turn tan/dark brown and the coil breaks ....

another one, and for some reason it's just ME.....but the COIL crimped connections are through the form var of the wire, and so I caught on pants down....burnt through all the crap and soldered it, I think it's still on the vette today....only been a decade or so...maybe more....

BTW, 69427/Mike has said the OEM GM modules are reliable as hell, and it's the aftermarket China? crap that gives them a bad name....I tend to believe him, trusting his provenance......

 

Returning from a car show a couple of Sundays ago my 77 cut out instantly. I coasted into a gas station and called for a flat bed tow. I was 99% sure it was the HEI module. Couldn't get to repairing it for about 3 days. Bought a new module installed it and it fired right up. I will carry one with me now. This is my second one to go bad in 21 years on my 77. I did notice the distributor was looking tired inside so I will be getting a MSD from summit.

 

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Soon I will replace my Stock HEI distributer with a High Performance complete set with twice the spark of the stock unit. I have a stock L48 with only about 46,700 original miles on it which just passed emissions today with flying colors Way below the standards they set for the test on a Dual high flow CAT exhaust system and Flowmaster Super 40 Dynaflow mufflers I am very happy. Back in 2009 Colorado took away the Collector Edition Plates for cars under 1981 thru 1975 than have reintroduced them again in these model years this year again. To qualify for the plates again we have to sign a paper saying we will not drive the car more then 4500 miles a year. For not a problem my Collector Car Insurance company limits me to 2500 miles a year on the 1977 Corvette.

Now with collector plates again I only have to have emission testing every 5 years. Sweet but cost me a butt load of money up front at $191.00 and change but will save me money over the life of the car. It will cost me half as much every year to register the car over the yearly price of $90.00 bucks a year and every 5 years unless they increase it only cost 15.00 bucks for an emission test. I will have to pay out about $45.00 bucks a year over the life of the car. I am just happy because sometimes when I fire up my L48 it sends up plumes of white smoke from unburnt fuel and it fired right up every time they did it today.

 

When I owned a 1972 El Camino with points the Timing was off and would fluctuate and also had this happen on a 1976 Malibu Classic this tells you the bushings on Distributor shaft have gone bad. At this point you have to buy a whole new distributor and I have done that twice in older cars. One HEI and the Points System. Anyone that has lasted over 90,000 miles on an Old GM HEI or Points Style and not had to replace the Distributor is lucky. The bushings go bad between 85,000 and 95,000 miles on these older engines in my experience.

Sad to say the older GM engines were never meant to last over 100,000 miles which is why the odometer turned over at 99,999 to 0 again. Todays cars will turn over to 999,999 miles which most are only built to last around 150,000 in the 1990s and after around 2004 they were built to last around 200,000 miles if they are well cared for. I had a 1998 Dodge Stratus that it would not pass emission testing anymore once it hit around 187,000 miles and it was 10 years old and very well cared for. Sold it for $1000.00 bucks to someone that lived in the emission free county. Told him when he bought it he would be dumping a quart of oil in it every 1000 miles.


I still own which passed emission by a very slim margin a 1992 Miata with about 180,000 miles on it. Failed the first round then I dumped half a quart of Seafoam plus a few ounces of another fuel injection cleaner into the fuel tank and topped it off with High Grade fuel. It passed emission by .12 under the maximum allowed at 3.5000 on the NOX emissions. I burned just enough carbon build up out of the heads to pass it by running premium fuel and running high rpms maxing it out between shifts at 5000 rpms on a 1.6L inline four banger. It failed by .23 the first time so it was 3.73 when it failed. Needs a new CAT and engine only has a little under 140 PSI and factory they are 193 PSI on a pressure gauge. That engine will either die or need a rebuild in the next two years. I am hoping my GF will buy another car by then. She drives my Miata.

 

My 82 with 236,000 miles on it passed emmissions well, repeat, well within limits when it last has an emission test for inspection about 2 years ago. Had probagly 225K on the ticker then. Was surprised how well it performed.