Took it for a leisure drive the other day, on the way home it started dying.. losing power (engine) not electrical, then back firing finally at a stop light died and wouldn’t start again did let out some amazing back fires though. Towed it home now need assistance with diagnostic work and repair advice.

 

symptoms of a gm hei module going bad

 

Thank you, not sure what that is? the coil? anyways it is a start appreciate the lead. will check it out and report back. tomorrow..lol too hot here now.

 

If you have a backfire you have ignition. Backfire can not happen w/o spark. However, could be On Again / Off Again scenario.

You have the first yr for HEI Ignition. The coil is on top of the distributor cap as opposed to round cylinder mounted in a bracket on the Intake Manifold.

Could be 101 reasons why yours quit. But here are some basics.

Loose coil wire at the dizzy cap.
Loose 12v supply wire at the cap.
Bad rotor
Bad cap.
Part time bad module.
Bad part time coil.
Bad spring bushing under the coil.

Your first exploration is to remove the coil dust cover. Three phillip screws. Check wire harness to that coil. Lift coil check the bushing underneath.
Second chore, put dust cover back on, loosen all four dizzy cap hold-downs.
Remove 3 -5 marked (with tape) plug wires from cap so it can be laid on its side.
Look for cracked cap.
Is spring bushing visible, dead center of cap?
Is there moisture or carbon tracking under cap?
Rotor condition?
Advance springs ok?
Rotate rotor and allow it to snap back.
Remove rotor.
Check wire harness to module.

Those modules were notorious for failing around 60,000 miles when they first came out. But hey, no more setting points, right?
With heat, the modge internal circuits would expand inside the modge. / open circuits, cutting off power.
Then after cooling off, completing the circuit.

An old trick was to place a Ziplock bag of ice on the dizzy, wait 5 mins. If it started right up, it was the modge.
This is why Heat Sink Compound was mandatory

 

ok, will do that first thing in the morning. check etc. and will report back. thanks everyone for all your insights and suggestions. look forward to trouble shooting this beast in the morning.

 

What does it do when you try & start it ? anything ? or totally dead ?

 

it cranks until I run the battery dead. sometimes it will backfire, but mostly it just cranks over without firing.

Did a few tests today as recommended by HeadsUP. everything seems to be ok. visually I have some pics.

not sure it seems ok to me.

seems ok to me but not a expert or any sort.

all wires etc were connected and tight.

 

Ok Soulbite, great pictures.

Disregard my instructions about the coil dust cover (3 phillips screws). That was for a MSD cap. You have the old Delco. That has some type of latch / lock to inspect the coil.

You have substantial amount of rust around the weights and springs of the mechanical advance. A good cleaning and a dab of grease would help things move smoothly.
But that's not your issue.
You still have a GM module. Who knows the date & mileage on that !!!!
Note the orange pretzel wire in your photo at the module. That looks a little iffy.
Weights have a number engraved. Not sure if that's GM or Mr. Gasket kit.

At any rate, I would at the very least swap-out the Module noting where each wire goes.
And replace the rotor, looks worn.
Perhaps it's time for new cap / rotor, coil & module. A new cap will have a new spring bushing included, but not the coil.

You may also want to shop for plugwire ID tags. Very helpful when the cap needs to come off the distributor and all the plugwires too.

When you swap-out the mudule, is a MUST to apply Heat Sink Compound underneath the modge and a dab on the distributor. Some new modges will come with the "paste". (do not use dielectric grease) Check on Ebay, they might have the compound. (RadioShack did)

There is always the slight possibility the IGN switch inside the steering column is giving you grief with the no spark issue.
However, noting your old GM modge, rust etc, the dizzy and parts are likely needing an update.

Some auto parts stores can check the module. If it checks-out ok, throw it behind the passenger seat for a spare, buy new anyway.

Maybe someone can verify the letters "W" and "G" on the right side of the module. Does that stand for White & Green? H-m-m-m-m-m

 

No spark, i'd start with module / rotor ( looks old crusty & corroded ) cap looks ok no burns or rust, but me personally for the small cost i would change that the coil & the wires too / inexpensive, easy to do & you now know you have all fresh stuff. If that doesn't do it / make sure it's getting fuel.
keep us posted.

 

Try to make sure it's an ignition problem, or a fuel problem.

Do you have a timing light, or a spark sensor? You can also pull a plug wire, and test with a spare spark plug (grounded to the engine).

Does the carb squirt if you pump the gas?

 

changed out the fuel filter, it didnt look too bad. there is gas when i crank it over. I have papa duty the next 3 days with my 5 year old grandson. I will try to get more done, and posted; but in all likelihood it will be monday before I can get back at it. I did order new plugs and a new module.




looks like I need to order some more parts any way. I would have gotten them from our local autozone, however it didnt have the plugs and wanted over $90.00 for the module, ordered it from ebay for $37.00

again thanks so much to everyone who is giving me their insight and expertise. Much Much appreciated

 

In the words of Scooby Doo, Rut-Row.

That is quite a price reduction on the modge from over $90 to $37.
I hope it's not one of those 5,000-mile guarantee item.

Anyway, did the new modge come with the compound?

 

In the words of Homer Simpson, "Doh!"

Soulbite, be aware that buying things like spark plugs, electronic modules, and the like off of eBay is a crap shoot regarding authentic vs. counterfeit – functional vs. junk. Buying retail offers a greater degree of confidence in the component but I completely understand wanting/needing to look for the best deal.

 

oops any whos...i havent actually gotten the module yet. But the plugs did come in. Sorry for the hiatus; grandson stayed longer than expected. But not long enough. but im am back. just waiting on the module to come in. I will post a pic of the plugs i got from ebay. I havent gauged them yet.

Hopefully, my module will come in soon and hopefully, it isn't a piece of trash.

plug i ordered from ebay.

 

Curious ? Why NGK Japan plugs & not A/C Delco ? Or Champion ?

 

I'm betting price.

 

And quality. I've only run NGKs for years. Pre-made plug wires, too.

 

NGK are recommended by many aluminum cylinder head makers.
In my case NGK had a longer reach, needed when using aftermarket heads.
They are a good plug . . . . . . usually.

Soulbite,
Just when you thought it was safe to go back in the water:

It seems several NGKs sold by big box / shipping companies were unknowingly selling NGK counterfeits.
You can Google for the story but basically the printing on the porcelain part of the plug was blurry on knockoffs.
And the number stamping on the metal was wonky.

I would think the "fake" issue is over and done with by now. It was a few years back.
However, I bought a 4-pack for extra spare plugs last yr from a huge company that ends in zon.
Three out of four plugs quit firing too early.
Coincidence? Maybe.

 

Not really specific in the brand. Local AutoZone didnt have them, they were going to order NGK, i thought i could order them instead and did. price was about the same. No disrespect intended to AC delco etc. They all are legible etc. so i guess we will just have to wait and see after install.

 

Yes I'm certain the plugs are fine. I run NGK's in my Vette as well. Very good quality plugs.
the cheapo module on the otherhand.......