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305 TPI Ignition wiring (NO SPARK)

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Old 04-08-2024, 05:30 AM
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305 TPI Ignition wiring (NO SPARK)

Evening all, I posted about this issue some weeks ago and I'm still struggling with it. I fitted a new dash harness to my 87 Firebird, 5.0L TPI. However, I now do not have a spark coming out of my distributor. What I have done and what I do have is as follows;
- 12V at my ignition switch power wires.
- 12V going into my ignition coil, and 12V in the Tach wire.
- 12V going to the distributor via the pink wire from the coil.
- correct injector pulse, the fuel pump also primes and the fuel rail has pressure.
- 12V at more ignition coil post.
- I have tested wire continuity through the power wires in the C100 firewall bulkhead, I have tested wire continuity to the ECM from the 4 wires that plug into the distributor ICM they all came back good.
I have fitted a brand new distributor, ICM and new spark plug leads as well. I have also tried grounding the ignition coil with a lead to the negative battery terminal to manually prove a ground for the coil.
I am stumped as to what could be the issue. By all accounts I have power going to the coil, to the distributor and all the necessary wires in terms of the ignition system have continuity.

If anyone can jump in and help please do.

TIA
Old 04-08-2024, 07:59 AM
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Re: 305 TPI Ignition wiring (NO SPARK)

Just because the parts are new these days does not always mean they work. I would start to look at components inside the distributer.



Old 04-08-2024, 08:04 AM
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Re: 305 TPI Ignition wiring (NO SPARK)

Have you grounded out a spark plug in a dark garage to see if they're sparking?

If you aren't getting spark at the plug then work your way back. My guess is the ICM, as it seems to be the culprit 90% of the time.
Old 04-09-2024, 12:04 AM
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Re: 305 TPI Ignition wiring (NO SPARK)

Thanks for the input guys, I agree that new parts these days aren't always the golden fix to issues, However, I also tried to start the car with a dizzy and ICM from a working Firebird before fitting the new ones. Still the same result, 0 spark at the plugs.
I feel it must be a wiring issue but I'm unsure where to continue testing for it.
Old 04-14-2024, 08:25 AM
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Re: 305 TPI Ignition wiring (NO SPARK)

Basic coil test. 12v on + side, with a jumper wire connected to - side and for now not connected to anything. Coil output wire, connect a spark plug and lay it on the engine somewhere to provide a ground to the threaded portion of the plug. With key in run, 12v on the + side of coil. touch the jumper wire to ground and spark plug should fire.
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