How I diagnosed my Onan generator

[Trempert]

The issue I was having was that my generator was randomly stopping - especially when it was hot outside.

1. Generator stops
2. Open the generator cover
3. The start switch will have a light blinking. That is your first number. It is probably blinking 3 times and then pausing.
4. Press "stop" once to read the next code. It will be some blinks (count them) followed by some more blinks. The number of blinks is the error code. 4 blinks then 7 blinks is 47.
5. Restart the generator (if it will start) and when it stops again read the error code. See if there is a consistent error code. Mine was all over the place telling me the error codes were bogus. Everything from take it in for service to wrong hertz to adjust voltage output.
6. If the generator won't start, prime it by pushing down on Stop button (do this from outside) for about 30 seconds. Do you hear a clicking sound from the fuel pump? If so, the fuel pump is sucking air and not fuel. This will happen for a few seconds during the first start of the day but should not happen continually.
7. If it doesn't stop clicking, let the generator cool for several hours and try again. This will help you diagnose if it's a fuel issue or not.
8. Does the generator run (even for just a minute)? If so, I determined that it was not getting fuel and when I forced fuel by priming it ran.
9. Fuel starvation is the cause: Onan will never find it because they test the generators with their own fuel source when you take it in for diagnosis.
10. I replaced the fuel filter ($15) and put a swim noodle on the fuel line to insulate it from the extreme highway heat. I believe the problem is solved. No problems yet........
11. If the generator stops again then see if the pump is clicking or running quiet. You will know if fuel starvation is an issue.

[AquaMan]

On my 5500 I could see the fuel line vibrating, which was telling me that their was vapor in the line and holding the prime button for a couple minutes told me I had a serious vapor lock. We were stopped at a lookout in SD while I was trying to diagnose why my generator stopped working. It was 95+ that day. After about 5 minutes of cooling off, the generator started again and rain fine for a few more hours. Ever since that day, I haven't had a problem, although it's never been that hot either. I did adjust my altitude, which I think helped some.

[Trempert]

PS - if you have a transfer switch you will need to bypass that for a period of time or, in my opinion, you will never know where the issue is.