Onan RV QD 12,500 generator running rough

[Piros1]

So I have a 2015 Newmar Essex with a Onan RV QD 12,500 onboard generator with only 635.8 hours. I purchased the Coach in 2020. From the beginning of ownership the generator has run rough. When I first purchased it the generator did not want to stay running when first started but would some times run after you started it a few times, at that time it was still running as if it was over fueling. First I know it is diesel and it does not have a choke but for comparison the way it runs is similar to a gasoline engine with the choke partially closed. So for what I have done so for. I have changed the oil twice, replaced air, oil, and fuel filters, new belts, and all three injector nozzles. (When I pulled the injector nozzles one was obviously bad.) This seemed to help and at least it will stay running but still runs as if getting an unbalanced fuel to air ratio. I checked all the intake passages to the air filter as well feeding the engine and did not find any obstruction or blockages. I plan to remove the injector nozzles again since it has been over a year so to check their condition.

This is my second coach with the same or similar generator. The other coach a 2005 CC never gave me any performance issues of this type other than a bad connection once on the primary controller board and a faulty low oil sensor. Both were completely different scenarios.

Any ideas or experiences would be appreciated. I could not find anything similar in the forums or on the web.

[twinboat]

Need to get the injection pump gone over.

The injectors are just nozzles, fuel delivery is from the pump.

[Piros1]

Thanks Twinboat I was considering that as a possibility but with such low hours I was making sure yo rule out any other possible issues. Right now it only has 635 hours, when I first got the coach it had less than half that, 250 or so I think. I will definitely keep an open mind as I move forward. It is man made and mechanical do it may have a flaw from the get go. I will continue to post what I find.

[RVFunlovers]

After you get the generator running and warmed up what is it doing?
Is the exhaust normal? Does it handle a real load just fine?

I have had a couple of these generators and while not bullet prof they tend to purr with almost not change in sound after they are running. What causes it to run ruff? A change in load or just every so often it changes rpm / sounds?

We just spent a few days at the Tampa super show and they had a power problem in the RV parking areas. We were surrounded by Entegra’s and Newmar’s, and most use the 10KW or 12.5 KW Oman’s. We were talking about how perfectly smooth they were all running.

[153stars]

Is it possible your drawing air through bad/cracked inlet fuel line or connection.

[Piros1]

Originally Posted by RVFunlovers

After you get the generator running and warmed up what is it doing?
Is the exhaust normal? Does it handle a real load just fine?

I have had a couple of these generators and while not bullet prof they tend to purr with almost not change in sound after they are running. What causes it to run ruff? A change in load or just every so often it changes rpm / sounds?

We just spent a few days at the Tampa super show and they had a power problem in the RV parking areas. We were surrounded by Entegra’s and Newmar’s, and most use the 10KW or 12.5 KW Oman’s. We were talking about how perfectly smooth they were all running.

(This is my second coach with the same generator, the first one ran smooth as silk.
It runs rough and loaded up consistently. You can see it in the exhaust and hear it.)

(The exhaust is black as if running rich. It does handle a load but runs rough and sounds loaded up.)

(Correct normally they run very smoothly.)

[Piros1]

Originally Posted by 153stars

Is it possible your drawing air through bad/cracked inlet fuel line or connection.

I don’t believe it is drawing air, it is running rich more so than just rough.