I have a 91 GMC Jimmy (full size) leaving my stuck in the driveway. My wife drove it the other day and it turned off in at a stop sign. It will turn over but will not fire. I towed it to the house and have been messing with it for 4 days now. I have good fuel pressure and no spark. The Spectra Premium Distributor and BWD coil are about 3 years old and about 4000 miles on them.

I followed this detailed article for troubleshooting:

http://easyautodiagnostics.com/gm/4....ed-icm-tests-1

I have no spark to any cylinder, no spark from coil to distributor, good 12v to pink wire at ignition coil with key on and running. I hung tested a new ignition coil with no changes and I tested my ignition module at the auto parts store and it tested ok. So then I replaced the pickup coil for $20 even though it ohmed out ok and didn't have contact to ground through the distributor shaft. I didn't have a lot of confidence this would fix the issue but for $20 I was tired of staring at a broken down truck. After disassembling everything and reassembling, the truck fired right up and ran great of and on a for about 10 min while I reestablished the base spark advance. I thought I had everything set and I went to put the air cleaner on while the truck was still running. As I lined up the air filter and began to screw it down the truck died and now I am back to no spark again.

I am thinking I have a short/ground condition somewhere. Looking at the wiring diagrams for the truck found on this link

http://www.gearhead-efi.com/Fuel-Inj...Information-42

I was wondering where to start again. I dont suspect any bad components since it ran flawlessly until it didn't. I think i just need a good route to troubleshoot to find what is giving me problems.

I had some questions for the smart people in the group,

1. When I checked my 12v pink wire at the ignition coil with the key off, I had continuity to ground, is this correct? If not I would think this is my ground condition. I do get 12v with key on and running. I am assuming a short/ground condition on this circuit would now allow the distributor to create spark.

2. What is the best way to check the signal wire coming from the distributor pickup/module? The article above noted to use a led test light. I didn't have a test light but I adapted a 12v power adapter for a USB charger which had an LED. I plugged my adapter into the tach wire coming from the ignition coil and did not observe any flashing.

Thanks in advance for anyone who might have some good advice, I will be out there trying to figure things out.