Weird Problem - Is it fuel or electric?

[Jeff W]

I would:
1) warm up to get into the "no start" situation.
2) pull a plug wire off of the spark plug side and insert a spare spark plug on the end of the wire.
3) ground the metal base of this loose spark plug against a bare piece of metal such as an unpainted valve cover bolt or bracket.
4) have a helper crank the engine (trying to start it) while you are watching for the nice strong spark from that plug.

There are other ways to check for spark but this is a nice safe process that keeps your hand out of the fan.

Should help narrow your problem and show you which fork (gas or ignition) you need to go down.