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Leading coil not firing

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Old 09-16-16, 08:24 AM
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Leading coil not firing

Trouble shooting my 100% stock 1990 GXL.
After working my car, (Replacing OMP and ECU) my car is still running very rough. tests show that the Leading coil is not firing at all. I have replaced Plugs and wires with NGK . Using a timing light, I see that the Trailing coil is firing and thus the car will start, but is very rough. I had a extra (stock) leading coil and it gave the same problem.
To prevent anymore throwing of tools and loud vulgar language in my garage.... I would appreciate some suggestions of what to look/test for.
Old 09-16-16, 09:00 AM
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The coil needs proper grounding to work so it has to be bolted firmly to the fender surface and the surface should be clean. Additionally the Black/Yellow wire to the coil needs to have 12 volts w/key to on. if that checks out then the other wire which is Green/Yellow is the trigger wire. If the main pulley was rotated by hand and w/key to on the voltage should alternate between two numbers and those numbers are 0 volts and 5 volts. The main pulley can be rotated simply by rotating the alternator pulley. The voltage reading should be 0 volts and briefly changing to 5 volts before returning to 0 volts.

Last edited by satch; 09-16-16 at 09:44 AM.
Old 09-16-16, 10:24 AM
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Are there any fuses or relays to check?
Old 09-16-16, 11:11 AM
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If your trailing coil is working then no.
Old 09-16-16, 11:25 AM
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Originally Posted by Only The Rotary
Are there any fuses or relays to check?
Check the wires Satch said to check.
Old 09-20-16, 10:20 AM
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All of the Electrical Tests that Satch suggested were done and the output is correct.
Soo, since the power coming into the Trailing Coil/igniter is correct, and the Wires and plugs are new, then it appears that I have a bad coil. I will be getting one soon.
The part that still concerns me is that the engine runs VERY rough and smokes a lot.
I understand that the Trailing coil is mostly for emission control and that the car should be able to run on just the Leading coils. I have a feeling that both coils may be toast.
I'll see when I get a different set of coils next week.
Old 09-20-16, 11:04 AM
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I find it weird that you tried 2 coils and both didnt work. have a feeling its not your coil.
Old 09-20-16, 11:39 AM
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I also thought these wouldn't start without the leading firing
Old 09-20-16, 11:57 AM
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Originally Posted by lduley
I also thought these wouldn't start without the leading firing
It would likely struggle to start but it should/could start.
Old 09-20-16, 11:58 AM
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Originally Posted by Only The Rotary
All of the Electrical Tests that Satch suggested were done and the output is correct.
Soo, since the power coming into the Trailing Coil/igniter is correct, and the Wires and plugs are new, then it appears that I have a bad coil. I will be getting one soon.
The part that still concerns me is that the engine runs VERY rough and smokes a lot.
I understand that the Trailing coil is mostly for emission control and that the car should be able to run on just the Leading coils. I have a feeling that both coils may be toast.
I'll see when I get a different set of coils next week.
If the engine was running on just the trailing coil then that would explain the roughness etc.
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