Onan generator shuts off after 45 minutes.

[RJay]

It could be that the demand of both fuel pumps running at the same time creates more suction in the tank than a partially blocked vent cap can handle and that the engine fuel pump is more powerful and able to overcome the suction.???

[ImagineIF]

You have something restricting an adequate flow of fuel, as proven by opening the gas cap. This could be the cap--if vented, the fuel tank vent, or the GenSet's fuel filter. I'd probably start with the GenSet's fuel filter given the RV engine runs fine.

[Stump Jumper]

I think that I will do just that. 1) Replace generator fuel filter. 2) Replace fuel cap. If that doesn't fix the problem, I will have to bite the bullet and try the fuel pump, but at $240 for the pump itself, that will be a last resort!

[RJay]

Stump,
Before you replace the fuel pump disconnect the output from the pump and crank the engine. If you have sufficient output the pump is good.

[Pubtym]

Originally Posted by thepratts

Had same symptoms with a bad fuel pump. Replaced it and all was OK. It was also an Onan 5500. It is not hard to replace, it is under the generator. It looks almost like a filter but has two wire going into it.

Replaced filter. Replaced fuel pump. Could not get generator to run. Cranks good. Discovered fuel pump not running. No power to fuel pump. Checked power to pump and connecting blade connectors. No voltage at those connections. Jumpered the fuel pump wires to the house batteries. Pump works. Generator starts and runs.

Question: Where do the wires to the connecting blade connectors end? Is there a 12 V fuse or CB that controls power to those connectors?