Spark weirdness

[DjEep]

Problem "solved", but question unanswered. I was helping "lovemybus" troubleshoot a miss in cylinder 2. When I'd pull the #2 plug wire at the dist, the miss would remain, but as I'd go to put it back on, it would fire and the engine would run smoothly. But, as soon as it was back on fully, the miss would return. So the cylinder would fire when the spark was arcing to the wire, but not when the wire was fully connected. Swapped parts until a "new" old plug solved it.

???

[Amskeptic]

Problem "solved", but question unanswered. I was helping "lovemybus" troubleshoot a miss in cylinder 2. When I'd pull the #2 plug wire at the dist, the miss would remain, but as I'd go to put it back on, it would fire and the engine would run smoothly. But, as soon as it was back on fully, the miss would return. So the cylinder would fire when the spark was arcing to the wire, but not when the wire was fully connected. Swapped parts until a "new" old plug solved it.

???

That is one of those weird ones with many antecedents. I have had that happen in all sorts of ways, including the coil wire coming from the coil.

What is happening, is that by pulling the wire a little, you are causing a resistance that actually collects and "heats up" the spark pulse. Plugs at the edge of function can be inspired to suddenly fire with this hotter spark. This is a great trick, by the way, for tired engines with lousy compression or those cold mornings where you fear you may have flooded the plugs. Pull the center wire out of the coil and keep it only 5/16 to 1/4 inch away from the distributor cap terminal.
Colin