trouble shooting weak ignition spark !!! Help

[Dave_Kriegel]

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 ?

[rickd]

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?

[Hal]

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

[Scott_Conger]

Hal's question as well, plus, are your spark plug wires copper conductors soldered to their terminations, or are they modern carbon-filled wires?

[It's Bill]

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

[Charlie B in N.J.]

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.