Two things come to mind. You didn't mention the year of the generator, so the first possible problem may not be relevant, but if you have points and a condenser they may be the problem. I've seen that before.
Tha other problem could be the LP fuel regulator. They are know to have problems with oil build up from the LP. They can be removed and reconditioned, but I have never done it.
Jim and Lynda, (Sophie, Jake, attack trained killer Shi-Tzus :-))
2003 Fleetwood Expedition 38N 2005 Saturn Vue