Troubleshooting help needed!! '93 Riv - was No Spark, now won't crank also!

OK, so I have a '93 Riveria, came out from work one day and when I attempted to start it, I heard something that sounded like the ignition blew back through the ignition. After that, the car cranked, but wouldn't start. I had the car towed home, started driving my other car. Problem is, now that car is having problems, so I need to get the Riveria back on the street ASAP!! My brother works weekends in a junk yard (he actually grabbed the car from the yard for me - clean, in decent condition, and nearly zero $$ in it). He'd had to replace the ignition computer (PCM, ECU - pick your acronym) in it, it wasn't operating one of the injectors. He tossed a couple of extra ECUs into the trunk for good measure, and I drove it from Ohio to Houston. I'm not getting spark, the diagnostic mode doesn't show any ignition codes (there's one code - r061c). I swapped out the ECU for a different one (and changed the PROM from the old ECU to the one swapped in) - and it wouldn't even crank. I swapped the old ECU back in, traded the PROM back into it - and now the car won't crank with it either!? I'm going backwards, it was at least originally cranking with the first module! I've checked the fuses interior to the car, they're all good. I have the factory service manual (I can find the "cranks, won't start" troubleshooting flowchart - but I'll be darned if I can find the "won't crank" troubleshooting flowchart, I assume there is one.) I've also swapped out the ignition module that mounts under the coil packs before I swapped the ECU.



So, any tips on at least getting it cranking again? How about the "no spark" condition?





ANY suggestions what to look at? HELP! I need at least one working car!!



Thanks!



Barrett

Check the wiring in the connector at the firewall. You probably have more than one break either at the firewall connector or in the wire. Brittle copper. Not on many cars, but on more than one the wires tended to break at or near the pin crimps usually within a mm or 2 of the crimp. Sometimes there is a break further back due to an incident (engine fire, collision repair) - you will have to look under the hood for hints that this may be the case.

Anyway -- that harness goes to the PCM which is likely why it seemed the old one was bad (if you did not actually test it you will never know... ) ...so you have to find the broken wires then uncrimp/strip/recrimp at good wire or splice in good wire. There is usually enough slack to let you do this. You can usually get repair pins/wires already crimped at full-line auto parts stores (I heard CarQuest has them, Rockauto.com carries many too). There's more than one thread on this - if you can't find it repost and someone should help you find it.

Albertj

PS - see if you and your brother can get your hands on a Tech II (GM's old handheld 2-way scanner) for troubleshooting.

Good point - with the flexing of the wires in getting the old module out, then swapping the new one in, it could easily have caused a brittle wire to break. IIRC, in the factory manual, there's a table with nominal values for the different connectors, so hopefully that will help me identify which conductor may have broken.

BarrettN wrote:

Good point - with the flexing of the wires in getting the old module out, then swapping the new one in, it could easily have caused a brittle wire to break. IIRC, in the factory manual, there's a table with nominal values for the different connectors, so hopefully that will help me identify which conductor may have broken.

There is a good chance that such a broken wire will be obvious on close inspection, although the insulation may not be compromised. Not sure it would be a problem on the '93, but that's what I'd be looking for.

Albertj

Well, turns out the table for the pcm connector values is for the car when it's running, so that's no help. I tried getting at the starter relay, looks like jumpering pins 1 - 4 should allow me to crank as the pass-key module only cuts power and doesn't have as complicated a function to bypass as the fuel cut-out. Only problem is getting it out, I can't see how the connector comes free, it looks like wires in a connector plug straight into the base of the relay, and that it's secured somehow. I's guessing that's what it is, given it's in the right area and has the right color leads going to it.

At some point you'll have to check the wires for hidden breaks. I think you're on your way. Good luck.

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OK, so I think I'm looking at two different problems possibly:

At first, car cranked, but no spark. I swapped the original PCM for a spare one, and put the ROM from the original PCM in it, car wouldn't crank. Swapped back to original PCM w/ original ROM, car won't crank.

Last night I got up under the dash and pulled the starter enable relay leads and bypassed it - voila!, the car cranks. So either the pass-key module is defeating the starter because of the anti-theft function, or it's doing the starter overide because it thinks the PCM is telling it the car's already running. I should be able to check the PCM signal that the motor's running tonight.

In the meantime, is there any special "gotcha" to swapping a PCM? I came across a pdf online that claims that the PCM for pass-key has to go through a "relearn" process of ignition on for 11 minutes, off for 30 seconds, repeated 3x. I've not found that in the factory service manual, although there's a lot in it and maybe it's tucked away somewhere unexpected. Anyone else heard of this relearn process (I'll try it, easy enough - it just got too late last night) or anything else to try when the pass-key module isn't enabling the starter (I assume fuel as well).

That being said, given the original problem was no spark, I'm probably getting this working just so that I can get back to troubleshooting the original problem!