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Onan generator
- Thread starter Rusty red
- Start date
Gary Dotson
501 Club
Just a little FYI, Most of the class "C"s have the Onan 4.0. They have been in service for many years and with minor changes, are still being installed in new units. This has a single cylinder engine and is the only model Onan has made that has no oil filter.
I had one a few years ago that had the symptoms of yours. Have you checked for fault codes? If I remember correctly, you push and hold the stop button and it will blink a code. I had to replace the control box, about $360 at the time, I'm sure it's more now. The repair manual wasn't a lot of help, the only other solution mentioned was the brushes. PM me if you think I might be any help!
I had one a few years ago that had the symptoms of yours. Have you checked for fault codes? If I remember correctly, you push and hold the stop button and it will blink a code. I had to replace the control box, about $360 at the time, I'm sure it's more now. The repair manual wasn't a lot of help, the only other solution mentioned was the brushes. PM me if you think I might be any help!
outdoors4evr
501 Club
Keep the troubleshooting basic. Spark, Fuel
Spark - Does it produce a bright blue spark when cranked?
Fuel - Is the fuel making it to the cylinder? Most RV's only have the fuel pickup line in the tank mounted higher in the tank (around 1/4 tank). Make sure there is adequate fuel in the gas tank. It may also have a separate fuel filter. Verify you have fuel at the carburetor.
Note: Sometimes it is easier to remove the fuel bowl from the carb than removing the fuel line to the carb.
Battery condition: The generator starting power probably comes from your coach battery and is "assisted" by the RV when the vehicle engine is running and the coach battery is charging. I find that it helps to have the vehicle engine running to spin over the generator engine faster for easier starts. My coach battery is a marine deep cycle battery which is not as well suited for high amp draw, but is excellent for slow drain use. The vehicle engine battery is a high amperage starting battery. Enough babbling by me.
Make sure your connections to the batteries are shiny and clean!
Spark - Does it produce a bright blue spark when cranked?
Fuel - Is the fuel making it to the cylinder? Most RV's only have the fuel pickup line in the tank mounted higher in the tank (around 1/4 tank). Make sure there is adequate fuel in the gas tank. It may also have a separate fuel filter. Verify you have fuel at the carburetor.
Note: Sometimes it is easier to remove the fuel bowl from the carb than removing the fuel line to the carb.
Battery condition: The generator starting power probably comes from your coach battery and is "assisted" by the RV when the vehicle engine is running and the coach battery is charging. I find that it helps to have the vehicle engine running to spin over the generator engine faster for easier starts. My coach battery is a marine deep cycle battery which is not as well suited for high amp draw, but is excellent for slow drain use. The vehicle engine battery is a high amperage starting battery. Enough babbling by me.
Make sure your connections to the batteries are shiny and clean!
I had the same thing happen last summer to my Onan 4KW microquiet when on the road. The flashing diagnostic codes said I the generator was not coming up to voltage at the end of the starting sequence. Like yours, the generator would run as long as you held the start button. I bought a HF inverter generator to finish the trip.
When I got home and took it apart, I found that one of the brushes had "stuck" and was arcing on the slip ring. New brushes and polishing the slip ring took care of it. It is quite a job to tear this one down and the brushes cannot be replaced without doing it.
Best of luck with this.
Ron
When I got home and took it apart, I found that one of the brushes had "stuck" and was arcing on the slip ring. New brushes and polishing the slip ring took care of it. It is quite a job to tear this one down and the brushes cannot be replaced without doing it.
Best of luck with this.
Ron
Gary Dotson
501 Club
You got lucky, Ron! I was hoping for bad brushes and even bought a set. I don't remember if I replaced them, or not, the originals were still in great shape.