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ThunderChicken 09-14-2021 04:27 PM

1988 z24i ignition modules overheating
The truck had a bunch of new parts thrown at it, starter, alternator, fuel filter, cap, rotor, plug wires, both coils, both ignition modules. This was all before I bought it. Orileys warrantied me a new set of modules and upon plugging them in and starting the truck it ran for about 40 seconds and quit. I look at the intake side module and it has a crack with smoke pouring out, too hot to touch. Suspecting a bad orileys coil and bad grounds, I ordered new coils and modules from rockauto and grounded the crap out of everything, checked codes on ecu(nothing), and no fuses are blown. They don't get hot if the key is on and they are unplugged from the coil. The truck just cranks if only one is plugged in. The rockauto stuff still heats up, but with aluminium foil behind them as a heat sink it'll run for 3 or so minutes before getting too hot. I had to build my own bracket to mount the coils and modules on, the original location was too rusted, but its all still grounded, I test everything with a voltmeter. I've done a bunch of research and can't really find anything, all that's left to replace is the ecu and wiring harness or convert this to another ignition system. Anyone have this problem or knowledge of how this ignition system is wired up? I'm also curious if the distributor has a stock ground location, and if the ecu is what sends power to these things. This truck is so cool but man these are expensive to replace. They have fins to dissipate heat but not this much heat. Napz is quite the interesting motor. Thanks in advance for any help

ThunderChicken 09-14-2021 04:52 PM

I got a morning off of school tomorrow and found a parts truck so I'm going to rob the whole ignition system off of it, plug wires to ecu. The fuel pump went out on this thing so it all should work. I'll test the resistance on those coils vs my new ones and see if I can get any results. Also might measure voltage from the power wire on the modules while the truck is cranking vs the key just being on. I'll keep the thread updated.

ThunderChicken 09-18-2021 12:35 AM

Parts truck was a complete bust, wrong year and motor than what the guy said over the phone. This thread and some basic gnition system resarch provided a lot of good information moving forward. Another 120 bucks on a new ignition module and also this jumper harness to bypass the modules from rockauto are my next steps. It appears as though either the ecu or these modules control the dwell time on the coils, this harness thingy should tell me that. If this isint the fix, then I'll probably order a new ecu and inspect the one in the truck very closely for anything weird looking. Still very interesting that this truck won't just run on one coil.

Stinky 09-18-2021 04:25 PM

My '86 Z24 ran on 4 plugs. Check your fuses....I was missing one.

ON an HEI in a Chevy, the pick-up coil, if bad, could cause this. I have no idea if this is the same type of system. Is there a star thingy under the rotor, on the dizzy shaft? If so, then magnetic pick-up for the stars is the coil. Also, bad coil(s) might do it.

You are using grease under the module right? It helps conduct heat away from the module.

ThunderChicken 09-19-2021 05:24 PM

Holy crap I think it might actually be the pick up coil. When I unplug the plug wire from the distributor and turn the key on they stay cool, and when I plug it back in they get super hot like right away. Thanks for the advice man!! Gotta figure out how to replace that now.

Deerhurst 09-19-2021 06:07 PM

Don't use just any grease if you want to use the body as a heatsink. A thermal paste will be what you want.

Sounds like it's probably a funky coil.

ThunderChicken 09-20-2021 01:47 AM

Ordered a complete distributor and two new coils just to be safe. I really hope this is the fix, Ill keep the thread updated with results. If anyone knows of a write up on distributor shaft replacement on these, Id be very thankful for a link. Seems pretty straightforward as long as I get the timing set right.

Deerhurst 09-20-2021 02:19 AM

Got a copy of the FSM?

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