Onan 4kw white smoke won't run, gas running out

Disconnect the fuel line at the outside where it attaches to the RV fuel system, not on the inside of the generator. I don't see how that would void the warranty; it's not an Onan-installed fuel line at that point. (You have to disconnect it on the suction side of the fuel pump anyway, and short of dismantling half of the generator, that's the only reasonable place to get access anyway.)