In electronics, we have a 50,000 volt spray that coats components with a kind of plastic/shellac. I don't know how that would hold up under vibration/heat/flexibility situations, but there is also a similar product marketed as "ignition wire" spray or something, various brands.
For all I know its the same product, but it might give your ignition (sparkplug) wires some extra life and stop shorts/arcing which may be preventing the cylinders from firing. For a $5 (hopefully) can of that, you might at least temporarily get rid of your problem.
Some mechanics I recall in the past spraying motors with WD-40, I can't remember if that was to drive out moisture or provide an insulating barrier to electricity.