Where is the fuse on the onan 5500 built in generator?

First verify that the breaker for the outlets is not tripped and make sure that the generator is running at full operating speed. let it run for 5-10 minutes and check for output power. If there is nothing, there are two possible problems. One could be that the automatic voltage regulator is bad. The other is that the field needs to be flashed - a high possibility if the generator has not been run in a long time. There are many videos on the internet that show you how to solve both of these problems. Just do a search for No output from a portable power generator.

It is right behind the start switch. There is one bolt that holds your start switch housing down, remove it and the housing. You will see the P1 connector with a lot of wires plugged into the control board

It sounds very much like no AC output from the stator to the run circuit, or the main PCB failure

Possible solution: if it's been sitting idle for some time, you might need to flash the windings. see this link:
http://www.endtimesreport.com/dead_gen.html
If you're uncomfortable doing it yourself, your Onan dealer can do it in 10 minutes.
Don't forget to check the circuit breaker on the generator itself!

Is your generator 4 kW or 4000 Model 5500.
If 5500 as on the picture over your question the reason may be short in the receptacles or low voltage/ rpm.
If 4 kW MicroQuiet, there the reasons may be too much, that you will nead a troubleshooting manual.

Do you have reading on the voltmeter. See the position of the switch under it. Try to reset the lights and the sockets.

Try to reset the AC breaker. If no success the field needs to be recharged.

on your generator ther is a reset if thats not it check for fuses if still no then u neda check the wires in the pluges if no then ur generator it self needs re bilt

there should be a fuse at the housing by the start/stop switch. if deisel then take the 10mm screw out of the coolant cap cover and check those fuses. verify power after. good luck.

Standard 30W motor oil.