ok, i went to start my 94 LT1 Caprice Wagon on friday morning and it cranked but never fired. so i jumped the two terminals on the data port to try to read the codes like i have always done on my old 93 Z28. well i forgot 93 was the last year you can do that, the speakers started making some goofy noises and the fans turned on. now realizing that i cant do anything with a 94 to check for codes without a highend machine, i decided to wait and check it out more in-depthly this morning.

left it until this morning.... i figured out there was no spark to the number 1 plug. so i check the coil, the coil wire is not sparking at all. i checked the harness to the ICM (ignition control module) and of the 4 pins, the 2 outside ones lit up my test light so i knew that was getting power. anyways, i check the coil wire to be sure that was fine.

upon removing the coil and ICM assembly, i began to back off the outer bolt that holds the whole thing to the head and the 3 wires with the ring terminals that attach to that stud broke when i backed them off, i ran them right into the ICM and snapped them all, and i THOUGHT i saw something spark when i did that. so ok, i finish taking it all apart (put 3 new ring terminals on the 3 wires) and swap the new coil in and try to start it. nothing again. now im sure its the ICM, i swap a new one of those in and still nothing.

now, i check the 4 pin harness with my test light that connects to the ICM and this time im not getting the juice to the 2 outer pins that i was earlier today. so now i know the main problem is im not getting juice to the ICM (or so i think). so does anyone know what the hell could have caused this.

here are my main questions/thoughts:

- perhaps i had a bad coil/ICM and thats why it wasnt starting initially, but would jumping those 2 top pins on the Data port cause something to get electronically messed up?

-why would i have power to that ICM harness 1 time, and then not have it 40 minutes later, could it be possible when i broke those ring terminals, i screwed something up?

-why would those ring terminals spark when i hit them on the ICM/stud or w/e if they are just grounds? (i believe it sparked however maybe im just an idiot)

any other thoughts or suggestions would be great, im pretty stumped right now.

PS, i also checked all the fuses in the dash as well as under the hood and all looked good.

 

You don't need a high-end scanner. You can find used Auto X-Ray OBD-I scanners for less than $100. You can download free scan software and buy or build a cable for less than $100. I'm assuming the 94 Caprice was still OBD-I (I honestly don't know if it was).... and if its not, its even cheaper to scan it.

If a ground sparks, it means you are completing a circuit that is pulling amps. Did it spark with the key on or key off?

 

the key was off.

if it makes a difference, i was jumping the battery while doing some of this work and i noticed when i put the 3 ground wires back on the head the underhood light got much brighter, then i pulled them off and it got dim but still stayed on.

im positive its OBD1.

 

ok. i figure out the reason i wasnt getting power to the ends of the ICM harness the second time around was because i had the coil harness unplugged which was the difference.

i'm pretty sure it's the opti, here is what i figured out...

i'm not getting an injector pulse which would come from the opti so obviously it's not doing that.
i also did this...
http://shbox.com/1/4th_gen_tech2.html#opti_test

and got no voltage. since the coil and ICM are brand new and one night it was running fine and the next morning wouldn't start, i'm almost positive it's the opti. i was going to try to pull the codes (paper clip method doesnt work and my connector is for OBD2) but i figure if i actually pulled them, the OBD1 computer probably wouldn't tell me a whole lot about what's goin on anyway.

i'm gonna order an opti in a few days and try that. i think i've pretty much nailed the problem, but any other thoughts or suggestions before i try this?