Hello all, working on one of the kids' car. A 91 Riviera. Stalled while idling (quite possibly ran out of gas) Then.....crank, no-start. I've been out of the business for over a decade, but we used to change alot of crank sensors for this, so I did. No joy! My next thought, Ign module. Had it tested.....failed. Replaced it. No joy! I have voltage to the module, but am unsure of which wire should provide ground, I have none that I can find. Tried an old cam sensor test on recomendation of a friend with no result. Any ideas?

Sounds familiar. You might want to look at my thread: https://www.gmforum.com/buick-172/90-buick-stalling-no-start-300509/

Well.... I got the GM trouble tree for 'crank, no start' from a friend still in the dealership.
Ruled out crank sensor and module. With a noid light installed now, and the entire ignition harness replaced (turns out I had some insulation issues) I now have injector pulse while cranking, no spark and the wierd thing....... when I stop cranking, the injectors go NUTS! I start getting random injector fire and fuel pump with KOEO after attempted starts. Probably more harness issues... any hints?

Normally at KOEO the fuel pumps runs for a second or two. That'* hard to catch if your working by yourself unless you have a meter, current clamp, etc. attached. Don't think you should have injectors firing during KOER!

I've seen shorted injectors cause this. You can check ohms or disconnect one at a time to find the bad one. It will usually start and run on 5 cylinders.

I got it!!! I was looking at the test to check the crank sensor and thought I would check the grey wire with the red tracer to see if it was grounding through the module. it wasn't. I fixed a random PCM ground and all has returned to to peaceful bliss!!