I am having difficulty addressing a no spark issue when engine is warm. It's not vapor locked, simply has no spark. Can sit a day or two and fires up. I have replaced coil, module and checked relays & fuses. No codes found when scanned. I am leaning towards a pick-up coil in distributor. What do you guys think? Cap and rotor should be changed, but not bad enough to cause issues.

Whats the battery output voltage when this occurs

New batteries. Gauges showing 14v

pick up coils do go bad from time to time.I would have bet good money it was the ignition module too.

What ecm... 1 or 3..........it wont start at all till it sets for a day ??

Did you replace the module with aftermarket or genuine ACDelco. ? Did you test the new module since you still have this issue ?

MEFI 1. Yes the new module was good, as it initially starred when installed. Of course the old one was working at that time too. Once you run it for a half hour and shut it off it then has no spark when you try to re-fire.

I verified the no spark condition with an extra plug wire and plug grounded with an alligator clip.

That is the same unit as a pass car distributor. They are everywhere used cheap. Hell, everybody should have a spare on board...

Anything else in overlooking that it could be?

Here is how to test the dist's pick up:
Part 6 -How to Test the GM Distributor Mounted Ignition Module

Earlier in article how to test module.

Remember, when the engine is running fine you will not find an issue. So, will have to test these things when not running. I know,,,, YEH ! :rolleyes