[T3] Arc's sparks and missing the mark's

Jim Adney jadney at vwtype3.org
Mon Jun 3 06:38:57 PDT 2019

On 2 Jun 2019 at 21:30, Keith Park wrote:

> Tonight I decided to see how sensitive it was to moisture, sprayed the
> distributor cap and it didnt react, but get the coil top a little wet
> and Im jumping all the way out of the center wire to ground, about a
> 1" path Usually when I see this I think there is an open somewhere that
> is raising the voltage needed to jump the gap and it finds an easier
> way to do it on the coil, not so this time, everything checks out. So I
> guess at idle a rather high voltage is needed for a good spark. 

If anything, the voltage required at idle should be lower, because the 
pressure inside the combustion chamber is lower. (Higher gas pressure 
makes a better insulator.) You're setting the SP gaps normally, at .027 or 
.028, aren't you? If you've gone to the larger gap that Delta says you can get 
away with sometimes, that will cause problems, but the problems I've seen 
have always been elsewhere.

Have you cleaned all the dirt off the nose of your coil, inside and out? That's 
one thing that I do occasionally, because black crud seems to accumulate 
there. It's also possible that you have a coil with a crack or track there. I've 
never seen that, but it's possible, and it's also possible for it to be so small 
that it's almost invisible.

Check the resistance of the HV coil wire. Some wiresets put a carbon core 
resistor wire there, and those can develop a break in the core.

Check inside your cap to make sure the carbon center contact is still there.

You could try sliding the rubber boot up on the wire, to see if that helps, as 
the problem/track might be in the boot or in the first inch of insulation on the 
wire. Normally, any spark would have to run up the inside of the coil nose 
and then down the outside. That makes for a nearly 3" track, which seems 
way too long for a sound, intact insulator.

Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA

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