91 TBI 350, No Start, No Spark

[sfara002]

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.

[sfara002]

Update...

I have code 42 (distributor signal) and Code 56 (fuel pump relay) present. I have a short data log if anyone cares to view it. Again, the truck turns over but no spark.

And I still have continuity on the pink wire to ground. I added a heated O2 sensor on this bus, would that create a contact to ground? I turned on the multi meter to beep and could not change resistance when I went through and wiggled the each section of harness in the engine bay.

I plan to have the ignition control module tested again tomorrow at a different auto parts store but not sure that will change.

[1project2many]

The O2 heater is a resistor connected between power and ground. Many continuity testers will show this as a complete connection although an ohmmeter should show some resistance.

[bdads]

ive had a coil issue before where the power wire was not making a good connection down in the coil itself--- so testing the wire shows power-- but the coil didn't get it,,, this would come and go intermittently.. I ended up replacing both the lead and coil to finaly fix it--- had this happen on a blazer-- and on a firebird !!!!

[whatif3387]

I had a similar problem where I would randomly lose spark and no power to injectors. This began shortly after installing a new distributor with new ignition control module that was included with the distributor. I swapped the ICM and would still give me the same problems. I traced a ton of wires and tested all kinds of stuff. The ICM tested fine. The problem still ended up being the ICM. Strangely the metal prongs that interface with the plug for the ICM were not making good contact with the plug even though it was plugged in. I had to bend them slightly in opposite directions from what I remember and now havn't had a problem since. So before even when it was plugged in if it jiggled the wrong way it would cut power to everything. That was incredibly hard for me to figure out. Odds are this isn't your problem but I know how tiring it can be to track down these kind of issues so I figured I would share my story with you. Maybe it will help maybe it wont either way good luck!

[sfara002]

Thanks for all the good support! I had the ICM tested twice at two locations as good. So I picked up a new one anyways, and the truck now runs great. I just saw the updates to this thread, looks like I might have had they same issue as whatif3387, I'll check the plug just to ensure I won't have issues with the new ICM. Thanks for everyone's help! Gearhead efi rocks, I hope others might learn as much as I have from this forum!

[cwkerr]

if you had the problem while putting the breather on you might check the wires going to the inj the little rubber insltr it they maybe touching the breather just a thought