No spark when plug is installed

[jimw]

Hello,

I have a 1982 Yamaha G1 golf cart that was working, but not running now. After some extensive trouble shooting I've narrowed down the problem (I think).

I doesn't make sense to me, but I get spark when the spark plug is not installed. Its good spark that arcs at least 3/4". When the spark plug is installed, I don't get any spark. As a test, I left the spark plug out, depressed the gas pedal and got good spark. While the engine was trying to start, I placed my thumb over the spark plug hole and the spark disappears -- remove my thumb, and the spark comes back.

It's the strangest thing! Anyway, all I can think is somehow the engine recognizes when there is compression present or not, and creates a spark when appropriate???

Any help would be greatly appreciated.

Thanks!

 

[bonduranth]

The spark is controlled by the flywheel turning. Check to make sure that the clutch is not loose. It may be just turning with no spark plug and not turning with your thumb over the hole. What is the compression? If good compression, change the plug. In my many years, I seen a plug or two that look great, but are bad (including one out of the box). Advance Auto also sells a device that allows you to simulate compression while watching the spark. I bought one and it works great.