I have been trying to troubleshoot a problem with the ignition. The car drove fine with no indication at all that there was a problem. Sat for 3 or 4 days without being driven . . . wouldn't start. Turn the key and it turns and turns with no indication of starting.

Here is what we have determined so far:

Does anyone have any experience with a similiar problem? What can we check that we are missing?

Thanks to anyone that can offer suggestions.

Sounds like a bad ign module.

Check your ignition coils first.
https://www.gmforum.com/trouble-shooting-test-procedures-141/testing-coils-spark-plug-wires-278818/

I may be wrong, but call Autozone, I think they can test your ignition control module(ICM).

Maybe it is the crank sensor.

That is a possibility Bob. If his scanner showed a bad cam sensor, then wouldn't it show if his crank sensor was bad, or no signal?

the scanner should show rpm in the data if it is showing rpm reading then the crank sensor is working. usually if the crank sensor is bad the fuel pump wont work either

I'd check over the VATs, try a different key, or do this to bypass it. https://www.gmforum.com/electrical-133/bypass-vats-92-99-a-279119/

I have a high mileage 93 with the 3.8L series engine. I had the same thing happen to me. After replacing and checking every sensor on the car, I decided to clean the grounding wires that are mounted to the ignition control module. It helped for a short time, then it happened again. When I decided I was going to have to tow the car to a shop to put it on the diagnostic machine, I thought I should change out the plugs and wires to eliminate that as a possibility. The plugs were pretty worn and the gap was very large. After I made sure the new plugs were gapped correctly and the I bloodied my nuckles getting the wires off of the back three cylinders, I started the car up and haven't had a single problem since. Sometimes, it'* the simple things that work! I now have about 5 or 6 backup sensors and an ignition control module on my shelf. It reminds me not to overthink a problem. Remember, the codes that are thrown are what the sensor is sending, not the problem itself. Before I tried the new plugs and wires, it wasn't showing codes because they are after the sensors in the logic of it all. Good luck and I hope this helps.

On my '95, any error I get related to cam or crank sensor means that entire circuit has to be checked. It goes from the cam sensor to the crank sensor to the ICM/coils. Those wires are a frail gauge, any nick in them will set it off. Do a search and you find one of the quickest ways to get a cam sensor error is to change your water pump, and nick those wires.

Check the wires and connectors closely. Then the coils, and pull the ICM and clean it.

This assumes you have pristine and solidly connected battery cables. Which includes pulling out the post and plates at the rubber ends that connect to the battery. And cleaning and resetting the connections at the starter and the ground that goes to the base of the engine block.

In 15 yrs with the '95, I have had 1 cam and 1 crank sensor error. One was a nick in the wire, the other was the ECM/PCM.

In other words, those errors aren't necessarily a smoking gun for that which is wrong.