trouble shooting weak ignition spark !!! Help

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trouble shooting weak ignition spark !!! Help

Post by Dave_Kriegel » Mon Jun 03, 2019 8:24 am

Well I have been working on a non starter 1917 for a month Zero compression, no spark Now with valve and ring job, new wiring, rebuilt coils still no start I have narrowed it down to a very weak visible spark when I lay the plugs on the block and rotate the cylinders into firing order . I have read on the forum years past that a weak spark visible on a plug OUTSIDE the block will result in no spark when the spark plug is chambered and under pressure. I am using modern F 11 plugs new, set at 032 I have strong coil noise New spark plug wires, The only thing I may think of since this is a non starter car is I used 12 gauge wire for both the 12 volt :?: :!: battery ground and running up to the ignition switch Could this thin wire not carry enough amperage ?? Any ideas ?

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Re: trouble shooting weak ignition spark !!! Help

Post by rickd » Mon Jun 03, 2019 8:34 am

What kind of shape is your coil box and switch in? Maybe some carbon tracking or some other kind of resistance holding back a decent spark?

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Re: trouble shooting weak ignition spark !!! Help

Post by Hal » Mon Jun 03, 2019 12:16 pm

Professionally rebuilt coils or .......?

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Re: trouble shooting weak ignition spark !!! Help

Post by Scott_Conger » Mon Jun 03, 2019 12:38 pm

Hal's question as well, plus, are your spark plug wires copper conductors soldered to their terminations, or are they modern carbon-filled wires?
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Re: trouble shooting weak ignition spark !!! Help

Post by It's Bill » Tue Jun 04, 2019 7:37 am

I suspect the gap. My antiques do well with about a .022 gap. Might be worth a try. Hope this helps, and good luck! Cheers, Bill

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Charlie B in N.J.
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Re: trouble shooting weak ignition spark !!! Help

Post by Charlie B in N.J. » Tue Jun 04, 2019 12:31 pm

Not sure about the wire size as it doesn't take much to fire the coils but, as mentioned earlier, "rebuilt coils" ? Done by who and were they properly set up on a HCCT or similar unit? If they weren't it's probably a big part of your spark problem. It simply MUST be done. No question. If they were done correctly run a larger size temporary wire to the coil box and check for a difference. Disconnect the coil box wire first though. A poor ground is another thing to check as in a clean timer. It's as bad as low voltage. I's also try a smaller plug gap. 0.30 for instance.
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