Generator Running Hot

Background...we have a new 2023 2552.  The generator has been getting hot and shutting down.  The longest I had running was 1 hour and it has been as little as 15 minutes.  This was confirmed by the dealer.  I'd like to get an idea of what others do with their generators.

For stationary operation, do people need to open the access door to aid in cooling?  What about when your coach engine is also running while stationary, any issues with your generator getting hot even with the access door open?

The dealer's service guy contacted Phoenix and all he got was "we've been building them the same way for 20 years and others don't seem to have a problem".  I don't buy that but I could be wrong.  The service guy was young but seemed pretty sharp.  He was running one test measuring ambient air and comparing to inlet cooling air...just one example of him puzzling through the issue.  He still had a call into Onan to get their input.

Thoughts would be appreciated.

We've had our PC for over 10 years with 5.5-6 of those full time. We avoid running the genny if we can but have run it for hours in heat under load on several occasions with no overheating problem.

It’s a defective generator issue, not a Phoenix USA design flaw. If your dealer service  department can’t or won’t easily resolve it you can go directly to Cummins Onan for warranty work or any generator service needs. If you didn’t get a Onan 4000 user’s  manual with your new coach  here’s a link to find the nearest Cummins sales and service location.

https://mart.cummins.com/imagelibrary/data/assetfiles/0043086.pdf

That is all interesting information.  To clarify, yes it is a shutdown condition.  The Onan panel is in place whenever it is run.  The code displayed inside is fault code 36.

I got it back from the dealer because we have our first outing this evening and we'll be running on shore power.  I tried to run it back at our storage unit with the access door open with the coach engine on.  It only ran for about 20 minutes before shutting down.  The service tech said that they were able to run it for about 1-1/2 hrs with the access door open...I didn't ask if the coach engine was on or not.

Ugh.  I can see this is going to be a frustrating one.  I'm not doing anything weird or unusual.  Prime fuel, then hit starter.  It cranks, starts, then let it run for a couple of minutes before putting a load on it.  The area I've been parked is just a fine gravel surface that is relatively flat.  The load is pretty much just the front AC.  No fridge, water heater.

Additional info...it did shutdown for the service tech with the access door closed.  He said he pulled the fuel line and ran it into a container.  He got bubbles from vaporized fuel (post shutdown).

I agree with CalCruiser, the genset is bad.  It is actually a bad idea to remove the front panel while it is running.  Presuming you don't have the fuel mixture too lean then you either have a bad sensor or fan.  Take it to Cummings, let them look at it.  I have run my genset 8 to 10 hrs a day with no problems.

That is all interesting information.  To clarify, yes it is a shutdown condition.  The Onan panel is in place whenever it is run.  The code displayed inside is fault code 36.

I got it back from the dealer because we have our first outing this evening and we'll be running on shore power.  I tried to run it back at our storage unit with the access door open with the coach engine on.  It only ran for about 20 minutes before shutting down.  The service tech said that they were able to run it for about 1-1/2 hrs with the access door open...I didn't ask if the coach engine was on or not.

Ugh.  I can see this is going to be a frustrating one.  I'm not doing anything weird or unusual.  Prime fuel, then hit starter.  It cranks, starts, then let it run for a couple of minutes before putting a load on it.  The area I've been parked is just a fine gravel surface that is relatively flat.  The load is pretty much just the front AC.  No fridge, water heater.

Additional info...it did shutdown for the service tech with the access door closed.  He said he pulled the fuel line and ran it into a container.  He got bubbles from vaporized fuel (post shutdown).

I had the same problem on my 2012. Exactly as you described. It was the fuel pump. Changed it and no more problems. I'd take it to Cummins as it's still under warranty. Good luck and safe travels.

Quote from: NCPinz on July 07, 2023, 06:37:28 am

That is all interesting information.  To clarify, yes it is a shutdown condition.  The Onan panel is in place whenever it is run.  The code displayed inside is fault code 36.

I got it back from the dealer because we have our first outing this evening and we'll be running on shore power.  I tried to run it back at our storage unit with the access door open with the coach engine on.  It only ran for about 20 minutes before shutting down.  The service tech said that they were able to run it for about 1-1/2 hrs with the access door open...I didn't ask if the coach engine was on or not.

Ugh.  I can see this is going to be a frustrating one.  I'm not doing anything weird or unusual.  Prime fuel, then hit starter.  It cranks, starts, then let it run for a couple of minutes before putting a load on it.  The area I've been parked is just a fine gravel surface that is relatively flat.  The load is pretty much just the front AC.  No fridge, water heater.

Additional info...it did shutdown for the service tech with the access door closed.  He said he pulled the fuel line and ran it into a container.  He got bubbles from vaporized fuel (post shutdown).

I had the same problem on my 2012. Exactly as you described. It was the fuel pump. Changed it and no more problems. I'd take it to Cummins as it's still under warranty. Good luck and safe travels.

Thanks for the advise.  The factor that multiple folks are saying "yep, run it for hours or days with the access door closed with it warm outside and no issues" leads me to a similar conclusion.  There are a couple of Onan service places in the greater Raleigh area so we'll get something scheduled with them in the near future. 

Do not run it with the access door removed.  There’s a warning sticker in place that states not to.  It’s all part of its own cooling system. 

I’d lean towards a bad fuel pump.   It’s doing exactly what mine did.  Sometimes it would run 1 hour, sometimes 5.  The fuel pumps are notorious for failure.   They are located below the cpu and it’s a couple hour job to change it out. After market pumps are about $30.  I relocated mine to the outside so it stays cooler and can now be changed out in under 15 minutes.

An easy way to find out if it’s the fuel pump is set up a gravity feed.  If it runs for hours on it that’s the issue. 

One of the problems of trouble shooting the fuel pump is if you simply disconnect from the carb and run the pump it will pump pretty steady. However the issue is once the pump gets hot it runs sporadically and shuts down. The pumps location under the cpu has virtually no air circulation. Many times even causes pulses that fouls the plug as well once it gets hot.

Unpopular opinion apparently but I had to take the front off of the compartment of mine out west at high altitude -- 8-10,000 feet above sea level at over 100 degrees. It did overheat and it was a new unit. And yes I adjusted the attitude setting. It was a 2005 at the time but probably the same Onan model generator.  I didn't have that many problems with the Onan generator on that PC but the one on my current one has been a nightmare.

One thing that many of the Onan service people don't even know apparently is the level of oil needs to be filled in a pretty tight range, a little below the marker. As in many of the problems people had were solved by removing some of the oil so it doesn't expand too much and become too full while the unit is hot. I just slowly removed oil until it was at a level the generator seemed happy and didn't overheat or run rough. This may not be your problem but look up some YouTube videos on this and you will see plenty of people have solved generator problems simply by removing some of the oil. I mean it's easy so why not at least try? Some of these people had basically spent a fortune replacing stuff to no avail and in the end the generator just had too much oil. Yours is newer than mine but they may well be using the same old Onan model.

I hope this helps. It's worth a try.