no spark with new coil installed 94 S10 Blazer
 

Hey all, Toby Hanson told me to post here as we are a bit stumped why the wife's truck won't start. (very angry look and toe tapping)

I have searched for roughly an hour an a half thru these forums and also at S10forum and not finding an answer.

1994 Chevy S10 Blazer 4x4 Vin W
unable to start truck
.. checked IGN fuse, looks good visually and test light liked it too
... checked for spark at plugs: nada
.... checked for spark after coil: nope
..... used test light on pink wire to coil and it lights up when key is ON
bought a new coil and installed it, turned key and no joy.

Toby does own the GM shop manuals and used that to check the ICM and removed and took it to Autozone and they tested: Passed
...New Distributer last August
....new Cap and wires and plugs at same time

Any ideas or a step by step testing plan??
Thank you in advance for the help.

Alex

maybe take the ingition module under the rotor in and have it tested - just a thot

Maybe just a bad coil, yes you can buy new coils that are no good

Alex took the ICM off and had it tested several times at AutoZone and it passed. We've also swapped another coil from another of my trucks and it still didn't make any spark. We also tested the pickup coil on the distributor shaft and that checked out OK.

I don't know these ignition systems terribly well. I'm wondering what tells the coil to fire. Is the crank position sensor involved in that process? We haven't done anything to check the CKP yet.

At last! The Blazer is running again! It had a bad ignition control module. You may recall...

> check the ICM and removed and took it to Autozone and they tested: Passed.

That was our problem right there. Autozone tested the ICM and it passed their test. They ran it several times on the test bench and it passed. However, after Tormatix went back through the ignition system testing things out he discovered that the ICM wasn't sending out the proper signal to fire the coil which is why he wasn't getting any spark. He swapped in one of my spare ICMs and—voilà—the Blazer fired right up.

The moral of the story is to never completely trust a parts store component test. Always follow the diagnostic tree in the manual.

thats the truth, cleaning my garage i brought in 3 starters i had laying around, they all tested bad... about 7 years later still using the same starter in my 86 that was bad