If it's engine trouble best place to start is with the LT lead and then go from there.
I speak from experience when i say that the LT lead is a pain, where it goes into the dizzy there is a little rubber gromet and it has been known for the said gromet to be knackered and thus you loose the power because it disapates the power to earth through the casing.
Don't know if thats any help but still, hope you sort it either way.