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Errant Spark - How to Fix

79 SC 3.0, stock. When I rev the motor, I get a spark from one terminal of the coil to the coil wire. I have replaced spark plug and coil wires and did not make a difference. What is causing this and how do I fix it?

thanks for your assistance.
Old 10-08-2019, 09:08 AM
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If it was me, I would clean the coil exterior with some brake cleaner and use some dielectric grease inside the hi tension boot to seal it.
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Old 10-08-2019, 10:02 AM
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Also, what is the right hand terminal connected to?
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Old 10-08-2019, 10:03 AM
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If it was me, I'd be tempted to dab that terminal with some liquid electric tape if Harry D's suggestion doesn't work. Don't know if you could find some kind of rubber cap to put on those terminals...
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Old 10-08-2019, 11:40 AM
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thanks, i will give all a try.
Old 10-08-2019, 12:59 PM
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Crack in the coil housing. Liquid electrical tape may fix it
Tony
Old 10-08-2019, 04:21 PM
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dielectric grease inside the hi tension boot appeares to fix it. Thanks
Old 10-09-2019, 08:08 AM
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This is a bit puzzling. Indulge me please. To me, I would think the zap would like to follow the easiest, shortest path. So, it seems odd that the discharge would find it easier to follow that incorrect path instead of just passing through the high-voltage cable going to the distributor cap, through the rotor, across the gap to the cap contact, and down the plug wire to the plug. Have you verified that high voltage wire is not open-circuit and the spark is also needing to jump some 'gap' in the wire itself? Or the rotor could possibly be open-circuit and causing a giant spark jump in there. Or, one plug wire is actually open? The point is, when things are working normally, the largest 'gap' in the circuit is the spark plug gap and the small gap between the rotor tip and distributor cap posts inside. That may constitute as much as 0.1", but here you have a much, much longer path crawling out of the coil tower and down to the terminal. That tells me either there is an abnormal 'gap' in the intended path, or there is a conductive path/crack in the coil tower all the way down to that post. Just my rambling curiosity here, a bit puzzling.
Old 10-09-2019, 08:20 AM
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Bob, thank you for your post. I agree with you that it is puzziling that a spark can jump an inch and not discharge through the spark plugs. That is why I posted the issue for the expert advise. What I know is it is no longer jumping at the current location after the grease... as it did.

The car runs smooth, but it did before. the spark plug wires have been changed, coil wire included and the issue followed. I will check the wires again but maybe I will swap the cap and rotor.
Old 10-09-2019, 08:36 AM
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Seeing a lot of sub standard wire sets out there lately. A diluted saltwater mix in a spray bottle will increase conductivity to force ignition to show any weak spots. Best used at night or dark garage. There should be zero stray sparking in factory Porsche ignition. This is really important as these cars begin to turn 50 years old as a slight fuel leak and stray spark make for a bad day. Below happened a couple weeks ago...




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Old 10-09-2019, 07:51 PM
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Quote:
Originally Posted by gold911 View Post
...the spark plug wires have been changed, coil wire included and the issue followed.
You mean the spark jumping issue or something else?
Old 10-12-2019, 04:06 AM
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