Check the fuel lines from the tank to the generator. Our 2004 B+ sat for 3-4 years with non-treated 10% ethanol fuel in the tank. This cause a few problems with the fuel system including fuel lines, carb and pump. The faulty fuel lines were replaced by Onan due to very small cracks and sucking small amounts of air into the system when the fuel pump was activated , full flow on fuel when dis-connected from carb. Plus it didn't help the operation since R-vision had installed a fuel line that was 2X over the required Onan size specification, causing the pump to heat up.