I recently purchased a 1991 Chevy C1500 2wd 5.7l TBI from a local school. According to their records it has a crate motor and a replacement transmission, and 118k miles on the body. I have no spark at all. I did the appropriate thing and loaded the parts cannon! New distributor, wires, plugs, coil, ignition control module - basically anything that made the spark work - I replaced - sometimes twice! I have 10.9 volts at the coil at the pink wire on both sides and going into the dist. Even with a charger on the truck, I never get better that 10.9 volts at the coil. No spark on the other side of the coil. I have checked the distributors (I have 2) and all of them are showing that the pickup coil is working (if I spin the coil with meter attached, I can see the coil work). I am also getting fuel out the injectors as the more I turn it over the greater the fuel smell gets. Even tried starting fluid - no help there. Any suggestions before I try a ritual cleansing and burn the thing to the ground, as it has to be possessed!! Thank for the help.

 

So, having loaded and fired the parts cannon, do you still think that was the appropriate thing to do?

What’s most likely the problem is only having 10.9 volts at the coil. Did you get that reading with the coil disconnected?

The power for the coil is sourced (via ignition switch) at one of the black fusible links on the firewall junction block. Since there’s likely discoloration due to age and/or previous repairs, you may need to remove them one at a time to isolate which one is actually powering it. Once you know which one is correct, check resistance between the fusible link eyelet and the pink wire (engine harness side) at the coil with the ignition switch in the on/run position. Anything more than 0.5 ohms indicates the fusible link, ignition switch, or related wiring is suspect.

 

Thanks for the reply. My other vehicle is a diesel, so part for this thing are stupid cheap. Loading the canon and firing really was cheap. When I researched the problem, it showed three parts that produced spark. Now I am finding that is not the case.
Doing some more testing I am not getting a signal from the ICM to the coil to send spark to the dist. Tried 2 different ICM's same results. Going to try a third here in a little bit. I did measure the resistance from the black wire to the pink on the coil and it came up with 22 M ohms. So that could also be a problem....
Could I run a wire from the lug to the pink wire, just to bypass all the other crap?
Thank you for the help.
BB

 

Update- I did try running a wire directly to the coil to increase the voltage to the coil - no luck. Three different Ignition modules tested. Two different coils. Two different distributors, both tested for pickup and they both work. Two different caps and rotors. No spark coming off the cap. Tried jumping pin A and C as some people suggested in other posts, no luck with that. Really running out of options on what it could be - unless every part I have thrown at it was bad, which I find very hard to believe.
Sitting down - totally stumped on the problem. Never had a vehicle act like this before, at least one this old. Newer ones with all kinds of sensors, yes. Older one usually just work.

 

Did you make this measurement with the key in the ON/RUN position? If so, then yes, this is the problem - cut off the fusible link and re-measure.

Bypassing the circuit provides power to the coil and ICM but there are other components that also depend on power from that circuit, so it doesn’t surprise me that bypassing it didn’t produce results.

 

Sorry for the late reply. I was so fed up I put the whole thing on hold.
I cut the fusible links out and no change in situation. Not sure where else to go. Probably going to start walking through the harness from top to bottom to see what might be messed up. I am also going to try disconnecting the computer to see if that makes any difference.
Thank you for your help and suggestions.
Bob