I have been having issue with my generator, onan microlite 4000. Has gas fuel pump works spark plug new filters are good. Took the carb off and it is clean. Nothing gummed in bowl or jets from what I saw. However, I get it going and all it does is rev up and down?Is the carb needing replaced or is something else up with it?

Hook up the fuel supply line to a gas can with a can of Seafoam cleaner in it....run the genny for a half hour and then shut it off and let it sit overnight.....the next morning run and if the "Hunting" or "Lean roll" is gone.....rehook up the fuel supply line.....if not the carb will need to be rebuilt.......

RVDisney wrote:I have been having issue with my generator, onan microlite 4000. Has gas fuel pump works spark plug new filters are good. Took the carb off and it is clean. Nothing gummed in bowl or jets from what I saw. However, I get it going and all it does is rev up and down?Is the carb needing replaced or is something else up with it?How many hrs. on it.

There are not many hours on it. I want to say about 250 is a good estimate. I do not use it often. I many run it to excercise it more than I use it. My main concern is making sure that it is the carb before I replace it. Can anything else cause this to happen?

I have been doing more reading on here. Some people had to replace the control box for the generator. How do I know if this is going. I remember reading that the box controls the idle speed which is an issue I am having?

96Bounder30E wrote:Hook up the fuel supply line to a gas can with a can of Seafoam cleaner in it....run the genny for a half hour and then shut it off and let it sit overnight.....the next morning run and if the "Hunting" or "Lean roll" is gone.....rehook up the fuel supply line.....if not the carb will need to be rebuilt.......I did this a few times AND I sprayed carb cleaner in the carb, following directions on the carb cleaner can. Worked after a while and has been great since...

Onan 4000 Revs up and Down | Good Sam Community

12 Replies

Supercharged
Explorer
May 05, 2014
RVDisney wrote:
I have been having issue with my generator, onan microlite 4000. Has gas fuel pump works spark plug new filters are good. Took the carb off and it is clean. Nothing gummed in bowl or jets from what I saw. However, I get it going and all it does is rev up and down?

Is the carb needing replaced or is something else up with it?
How many hrs. on it.
96Bounder30E
Explorer II
May 05, 2014
Hook up the fuel supply line to a gas can with a can of Seafoam cleaner in it....run the genny for a half hour and then shut it off and let it sit overnight.....the next morning run and if the "Hunting" or "Lean roll" is gone.....rehook up the fuel supply line.....if not the carb will need to be rebuilt.......

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Onan 4000 Revs up and Down

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