I don't have any suggestions on the technical side of this, but, to clarify, do you have an Cummins/Onan propane generator? Probably model # 3.6KYFA26120? Maybe described as "RV QG3600 LP 3000 Watt LP Generator"?
I would check the oil level first. I don't know how your fuel supply line is plumbed, but some are plumbed in such a way that the generator will not drain your fuel tank. If your fuel tank is getting low, I would think that could be a problem.