Onan marquis gold 5500 won’t stay running unless it’s connected to jumper cables

[Mac801]

I’m having an issue where my generator died in the middle of the night, batteries drained, and now when I start it with a jumper box or jumper cables it just wants to die out after a short while when I disconnect the cables, also my lights are super dim when the cables are not connected and the generator is running. 
 

Could bad batteries  cause it too just die out under any kind of load? 
 

Next thing I noticed is the idle arm with a spring attached to it if I push it up even just slightly the generator dies out. The fuel filter bowl only fills up about 8th of an inch to a quarter inch max while running. 
really just not sure where to start or what too look for.

Trailer is a 2008 new vision TH by k-z 

 

still doing research as I’m writing this for similar problems.