Onan Generator Problems?

[mjpachuta]

Hi Folks. I have a 2015 Precept 31U that,s been pretty good to us over the last two years ... except for the Onan 5.5K gasoline generator. We have maintained our generator per the maintenance instructions by running it with a 50% load every month and changing oil and filter at the first 50 hours. We have actually used the generator only five - six times, and it has shut itself down every time with a code 14 (over frequency) alert.
Following the first failure last year, we immediately took the unit to the nearest Cummins Service facility where they kept it for three weeks in an attempt to reproduce the problem. They eventually did reproduce the failure and replaced the carburetor under warranty.
This year the first time we used the generator, it ran fine for 2 1/2 days then shut down with the same error code. Then it failed after only 6 hours of running, then 3, then 1. Now the generator fails after 2 -3 minutes of running with no electrical load whatsoever, each time with the same over frequency code. The Cummins repair facility experts are stumped except to state that the generator is no longer under warranty. They cannot get the generator to run more than 3 - 4 minutes, even tough it starts without hesitation and the error is always the same.
While I continually work with the cooperative Cummins staff I was just wondering, has anyone else out there in the RV community run into a similar problem? Was there a solid solution?

[JFlightRisk]

Not an Onan expert, but it sounds as if the engine is running too fast. This can be caused by an air leak at the intake, carb and linkages not properly installed, misadjusted governor or broken governor. There's a very fine line between proper RPM's and overspeed, which will cause a high frequency reading. You would have to get ahold of a frequency meter, and get that measurement the minute it starts up, then call Onan back, and have them check the specs for your genset.

[kevfra]

If you have a smart phone you can load an app that will be basically a sound rpm, or frequency meter, to tell you exact RPM you are spinning.

[eldermike]

I agree that it sounds like what is called a vacuum leak. The intake manifold might be cracked or just a simple gasket issue. Since they identified the carb as the issue it seems they thought it might be leaking air and could not be controlled by throttle position. I think they were right but the leak was one more part under the carb and not the carb itself. It's a guess but something you should run by them.

[abarkl]

It is probably a bad fuel pump. We owned the Onan 5.5k gasoline (HGJAB) for many years and besides having to replace the carburetor once for not running it monthly we had to replace the fuel pump once for the exact same symptoms you describe.
They are $40 on Amazon and take 15 minutes to replace;
https://www.amazon.com/Airtex-E11015.../dp/B0076D5OI2

[RyRoRyan]

Mention to them that you reported the problem before the warranty expired. Just because they could not fix it (correctly) before the warranty expired does not get them out of it. The other thing, is that they should have some sort of warranty for their work like 90 days, 6 months, 12 months something like that. If the same issue is coming back up within that timeframe, then you can bring it back on that pretense as well.

[Oklahoma Dan]

I had a fuel pump replaced on my Cummins Onan 4000W gas generator under warranty. The original Jayco warranty which includes my generator was about to end in 30 days. I specifically asked the Cummins service manager when I picked up my RV how long was this second fuel pump they installed going to be covered if something went wrong with it. I was told that when my Jayco warranty ends in 30 days that the parts and labor for this particular repair would not be backed by Cummins. In other words, you are done. Nice that I escaped paying over $700 for fuel pump and labor due to what was left on a warranty but here is a corporate attitude with customers that I will certainly remember and tell everyone I know when it comes to buying an RV with a Cummins generator.

[Big Bird]

Hi: I did not catch you indicating the required spark arrester blowout. On the CD that came with the our 35US unit it indicated it need done about every 50 hours. It also indicated the tools necessary to remove the plug (ratchet, socket, universal...) and that the plug was difficult if not visible. Basically remove the plug, run the generator, and replace the plug. Just a wild guess but...

[mjpachuta]

Well, after the Onan repair facility had my 2015 Prececept 31UL for a month, they finally found the problem with my 5500 generator to be a "governor gear" contained in the lower end of the engine. This had started to disintegrate after only 200 hours on the generator. In the end, Onan covered 80% of the repair costs even though I was past the 2 year warranty, and my service insurance covered the remainder of the cost (less $200 deductible). Now I just hope that this problem does not reoccur. I will continue to exercise the generator every month with a 2-hour half load run.
Thanks for all of your feedback folks.