Old thread I know, but has this been resolved "officially"?
Are the two plugs in parallel, or (as would be better) in series?
If, as above, they are in parallel, then, yes, one shorted plug would sap all the spark energy from the other plug. THAT would mean if one plug was fouled then the other wouldn't get spark and they couldn't run one one cylinder.
But we all know they can, and do.
Hence I contend they are wired in series. One HT coil, completely isolated from the chassis (ground) and isolated from the primary winding.
When the primary current is interrupted by the pints opening, the inducted HT current goes to one spark, through the chassis to the other, then back to the other side of the coil secondary winding.
So both plugs fire together. If there is any short circuit from one plug to ground (wet plug, cracked insulator, dirt etc) the other plug will actually see more energy than if it was sharing the spark with the other plug.
In multi-cylinder engines (Commodore Ecotec V6 comes to mind) this is how I believe they run them. They are wasted spark with two cylinders sharing one coil. Hence they have three coils.
So if one plug fails (short circuit) then the other one of the pair still runs fine. You only lose that one cylinder.
Now there's a thought... I wonder if a Commodore V6 coil could be adapted, using a 12Volt SLA battery and the Victa Twin points?
