Is there an inline fuel filter besides the Onan filter

klutchdust wrote:

The trailer is not far off from being level, it's in my backyard.

It will cost you nothing to level the trailer.
What is "not far off"? When dealing with liquid spread out over an oil pan maybe 12" x 12" not far off can make a difference. If it is 1 inch off over the 8 feet it will be 1/8" difference from one side to the other on a 12" oil pan. Are there any blinking lights on the generator panel when you try to start it? 2 blinks indicate low oil on many Onans.