RE: onan generator - no spark
You stated that if you spray either into the engine it will run on one cylinder. Have you gone thru the carburetor and cleaned the mixture jets yet? Sounds like you have a clogged fuel circuit. If spraying either gets it to run at least one cylinder, you most likely don't have a "spark" problem. I'd look into the carburetor.
RE: New 2012 Jayco Greyhawk 31SS
We bought our 2010 Greyhawk 2 years ago and no regrets! We don't get to use as much as we'd like but this has been a great RV far. The floor plan has worked perfect for us and our 2 large labs.