Check the plug first. I assume it's completely clean between the centre electrode insulator and the body. It's also possible that there is a crack in this, difficult to see. Instead of grounding the plug see if you get a spark from the HT lead itself - you may have to stuff a wire into it. Don't recommend sticking your finger into it to do this though!
If it isn't the plug it'll have to be the coil.
wes, March 2009
