I have been reading many threads about these 4000 microlite issues that people had. However, I have yet to find one that applies to my situation.Okay, so went to start the genny when I gave it prime etc. It starts and runs but never gets up to rpms it sputters. Then it dies. No matter what I do I get the same results. I took the carb off cleaned it and the solenoid on the carb. All were clean I did not find any crud in the carb bowl etc.. I sprayed it all down and put it back in same results. Tried new plug same issue. What can be my problem and what should I try next. Also, pump is running because when primed I heard the gas go into the carb bowl.

Stupid question, but do you have enough gas in your tank ? Most generators won't run if it's down around a quarter tank, but you probably know that.

How long has it been since the generator was used, and worked properly? Was it Exercised monthly since then? Do you treat your gasoline with Stabilizer? It doesn't take long for varnish to build up in an ONAN carb, and the slightest bit will really louse it up. There are ecopolitical reasons whey ONAN doesn't offer carb repair/rebuild kits but the fact is they (I'm thinking the KY series ONAN) carbs are very difficult to clean.My guess is there's crud in the "idle" passages. Remember, an RV GenSet is a fixed-RPM unit. 3600 if it's a KY which I expect it is. That means the "Idle" circuit has to work all the time. Some KY series had a Low Oil Switch, but later Spec Codes deleted them as they were troublesome.Post the full Model Number (last character is Spec Code) and we can find you a Service Manual. No point in blaming and testing an Oil Switch you don't have.The genny gurus hang out on the Tech Issues Forum. Might be a good idea to hit "Notify Moderator" and ask this to be moved there.

The Onan generators have circuitry that shuts down the generator if it is not operating properly.

I had this one time ,run stop had to buy a new carb.

Onan 4000 Start Runs and Dies Issue | Good Sam Community

j-d
Explorer II
May 05, 2014
How long has it been since the generator was used, and worked properly? Was it Exercised monthly since then? Do you treat your gasoline with Stabilizer?

It doesn't take long for varnish to build up in an ONAN carb, and the slightest bit will really louse it up. There are ecopolitical reasons whey ONAN doesn't offer carb repair/rebuild kits but the fact is they (I'm thinking the KY series ONAN) carbs are very difficult to clean.

My guess is there's crud in the "idle" passages. Remember, an RV GenSet is a fixed-RPM unit. 3600 if it's a KY which I expect it is. That means the "Idle" circuit has to work all the time. Some KY series had a Low Oil Switch, but later Spec Codes deleted them as they were troublesome.

Post the full Model Number (last character is Spec Code) and we can find you a Service Manual. No point in blaming and testing an Oil Switch you don't have.

The genny gurus hang out on the Tech Issues Forum. Might be a good idea to hit "Notify Moderator" and ask this to be moved there.
Mich_F
Explorer
May 05, 2014
Stupid question, but do you have enough gas in your tank ? Most generators won't run if it's down around a quarter tank, but you probably know that.

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Onan 4000 Start Runs and Dies Issue

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