Yellow Spark No Start

[HotWheelsBurban]

Wild Guess: It wasn't the rotor burn-through that killed the modules.

The high firing voltage killed the rotors AND the ignition coils. The failed ignition coil then killed the module.

The failed coils could still provide (weaker) spark, but they'd draw excess current from the module to do so.

Repeat module failures of name-brand, properly-made modules (excluding Communist Chinese bottom-feeder crap) on HEI is nearly always due to a problem that begins when the insulation on the wires inside the coil fails, so the wires short to each other. When they short to each other, the resistance goes down and so the current draw goes up.

That makes sense! I wasn't working on cars much then, just selling and fetching parts in the store ( I was in grade school then). But I can definitely see that, especially if people didn't push the coil wires into the slots in the cap carefully, or got them caught in the coil cover and pinched the wires during reassembly.
At that time we had many service station customers, and some of them had fleet service contracts. So we sold a LOT of GM parts in the late 70s and early 80s. Then some of these fleets got rid of the Impalas and Lemans', and got Ford Fairmonts, and when those were worse than the GM's, then K cars. There was one fleet that was over 600 cars, driven every day in Houston, Texas area, so they were a great test bed for what would hold up to Houston summer and traffic. Of course this was also when a lot of people from up north came down to SETX, cause there were still jobs here and it wasn't as cold.
I did help Dad with the tune ups then, and he showed me how to properly assemble the cap/coil/cover package. So that became one of my tasks when we were working on our vehicles, along with tool fetching and reading the torque specs and setting up the torque wrench. Little did I know this was training for future endeavors....

 

[Schurkey]

Folks are lucky to have in-person mentors.

The internet is OK, it's "remote learning" with a hundred mentors, some of which are more "mental" than "mentor". But it's better than going it alone.

 

[Frank Enstein]

Getting a new coil and module when I get paid!

 

[Schurkey]

Getting a new coil and module when I get paid!

If this were me...I'd poke an HEI spark tester into the coil wire. If it reliably fires the spark tester, you almost certainly don't need a coil and module.

There was a time when I'd say that the new coil and new module "wouldn't hurt, except your wallet", but with counterfeit and Chinese junk parts epidemic in the industry, there's a real chance that what you buy "new" may not be as good as the old parts you take off.

 

[Frank Enstein]

I just want one of each on hand. I will save the old ones on the Astro shelf.
I am thinking about AC Delco or Standard brand parts. I can check country of origin on the ones I can get at work.

 

[Schurkey]

I just want one of each on hand. I will save the old ones on the Astro shelf.

I understand that! I've got an assortment of new and used caps, rotors, a module or two, and entire used distributors for my various vehicles. Even one nearly-new, (defective) distributor for Vortec, and one unused/new OEM Delco distributor for TBI.

As long as you're careful to get OEM-quality or better, you'll be wise to have spares. The prices on GOOD parts is not going down anytime soon, unless the economy totally collapses.

 

[Frank Enstein]

I put the new stuff in and it started even quicker than usual. Drove it around for 3 hot/cold cycles and it ran fine.

Now it won't start. It has to be something simple. When it starts it runs perfectly.

it has a strong spark, it's spraying fuel, and the timing is set correctly and didn't need to be adjusted (I thought it may have jumped time but no).

Borrowing a code scanner tomorrow and plan to clean and inspect all the grounds and all the plug in connections.
I also plan to unplug the temp sensor to trick the ecu that it's 40 below to see if I can get it to start.

Anyone have anything to add to the list of what to check?
I'm burning another vacation day and my wife can't work without the Astro so we lose a day's pay every day it won't run.

Thanks again folks!

 

[Schurkey]

Now it won't start. It has to be something simple. When it starts it runs perfectly.

it has a strong spark,

Where? At the coil? At the plug end of the plug wire?

What's important is spark across the gap of the plug.

it's spraying fuel, and the timing is set correctly and didn't need to be adjusted (I thought it may have jumped time but no).

Any chance you got some bad gasoline? If you crumple up a paper towel into the throttle bores, let the gas spray on it, can you take the paper towel out, put it on concrete, and have it burn furiously?

Borrowing a code scanner tomorrow and plan to clean and inspect all the grounds and all the plug in connections.
I also plan to unplug the temp sensor to trick the ecu that it's 40 below to see if I can get it to start.

Spraying more gasoline doesn't seem like it would be of benefit. I'm half-suspecting the plugs are fouled as is.

Anyone have anything to add to the list of what to check?

Four things needed: Compression, burnable fuel mix, spark across the gap, at the right time, and a relatively non-restricted exhaust.

Have you tried a cranking compression test? That also allows you to see the condition of the plugs. If the compression is uniformly low, you might have timing chain problems.

If the exhaust were restricted, it'd likely fire then stall, not fail to fire at all.

If the previous problem was a failed rotor, consider another rotor. Maybe there's something going on that's causing repeat rotor failures.

 

[Frank Enstein]

Thanks! I had a fleeting thought about the fuel and plug wires.

 

[HotWheelsBurban]

Where? At the coil? At the plug end of the plug wire?

What's important is spark across the gap of the plug.


Any chance you got some bad gasoline? If you crumple up a paper towel into the throttle bores, let the gas spray on it, can you take the paper towel out, put it on concrete, and have it burn furiously?


Spraying more gasoline doesn't seem like it would be of benefit. I'm half-suspecting the plugs are fouled as is.


Four things needed: Compression, burnable fuel mix, spark across the gap, at the right time, and a relatively non-restricted exhaust.

Have you tried a cranking compression test? That also allows you to see the condition of the plugs. If the compression is uniformly low, you might have timing chain problems.

If the exhaust were restricted, it'd likely fire then stall, not fail to fire at all.

If the previous problem was a failed rotor, consider another rotor. Maybe there's something going on that's causing repeat rotor failures.

On the early GM HEI, early rotor demise was usually from bad coils or wiring. Maybe there's too much resistance somewhere?