2021 Momentum 381 w/Onan 5500

[Hoopy Frood]

Hmm, I don 't know about that "notoriously finicky". This is our second one and they've both been trouble free. The first one ran on the same fuel tank fill for over 5 years. We didn't use it much but it always started and ran with no problems. I did drain the carb at the end of the season. This one has been troublefree too.

[msutoad]

Hmm, I don 't know about that "notoriously finicky". This is our second one and they've both been trouble free. The first one ran on the same fuel tank fill for over 5 years. We didn't use it much but it always started and ran with no problems. I did drain the carb at the end of the season. This one has been troublefree too.

Right now, my TH is at the dealer for some warranty work, but they are not an authorized Cummins dealer, so they cant do much. I will go through it with a fine tooth comb. I will also search for a mobile Tech, which I know will be covered by GD with the exception of the travel dollars given my dealer is not certified. I will keep this thread up to date once I get some more info from my own investigation, or from a mobile tech.

Thanks to everyone who has replied already!
Jason

[msutoad]

UPDATE TO THIS THREAD:
I spent alot of time with ONAN/Cummins on this, as well as GDRV. My testing showed them that the air intake to cool the genset was creating a tornado effect between the generator and the ground and the hot air exit from cooling the genset was being sucked back up to cool the unit, so it was overheating.
GDRV sent me a baffle that screws to the bottom of the genset, that vents the hot air away from the genset and my issue went away.
Attached is the Cummins part # as well as a pic of what I installed, super easy, problem solved!!!

[RoyBell]

UPDATE TO THIS THREAD:
I spent alot of time with ONAN/Cummins on this, as well as GDRV. My testing showed them that the air intake to cool the genset was creating a tornado effect between the generator and the ground and the hot air exit from cooling the genset was being sucked back up to cool the unit, so it was overheating.
GDRV sent me a baffle that screws to the bottom of the genset, that vents the hot air away from the genset and my issue went away.
Attached is the Cummins part # as well as a pic of what I installed, super easy, problem solved!!!

I am pretty sure mine is doing the same exact thing. It will startup and run no problem. Runs for 20-30 mins and then surges and shuts down. I will go to re-start and it surges and shuts down and not run. I let it sit for 20 minutes and it will start back up and surge and then start running normally. Then after a short while it will shut down again.

A couple weekends ago it was doing the same thing while camping. I was only running it during the day (75-80deg). The last morning the batteries were almost dead so I started it up and it ran just fine for 2 hours. It was 50-60 degrees out.

Did yours surge before shutting down or just shut down? I believe I had a similar code last time I looked it up. Just a generic "shut down automatically" code or something like that. I definitely get the impression some sensor is telling it not to run. The surging part seems weird to me though.

[msutoad]

I am pretty sure mine is doing the same exact thing. It will startup and run no problem. Runs for 20-30 mins and then surges and shuts down. I will go to re-start and it surges and shuts down and not run. I let it sit for 20 minutes and it will start back up and surge and then start running normally. Then after a short while it will shut down again.

A couple weekends ago it was doing the same thing while camping. I was only running it during the day (75-80deg). The last morning the batteries were almost dead so I started it up and it ran just fine for 2 hours. It was 50-60 degrees out.

Did yours surge before shutting down or just shut down? I believe I had a similar code last time I looked it up. Just a generic "shut down automatically" code or something like that. I definitely get the impression some sensor is telling it not to run. The surging part seems weird to me though.

Mine did not surge that I know of, and he outside temp only mattered and kept it running if it was below 50ish degrees.
The baffle was the game changing moment and when I spoke to Onan/Cummins engineering and escalation support, they absolutely knew about it and I told them how I diagnosed it and the were impressed I used saw dust under the trailer to see it recirculating then air and ingesting the hot air back into the unit.

Lemme know if you want pics directly from my uni versus the manual pics from Onan I put in this thread.

Jason

[RoyBell]

Mine did not surge that I know of, and he outside temp only mattered and kept it running if it was below 50ish degrees.
The baffle was the game changing moment and when I spoke to Onan/Cummins engineering and escalation support, they absolutely knew about it and I told them how I diagnosed it and the were impressed I used saw dust under the trailer to see it recirculating then air and ingesting the hot air back into the unit.

Lemme know if you want pics directly from my uni versus the manual pics from Onan I put in this thread.

Jason

After some troubleshooting I am positive I am having the same issue. I changed the fuel pump and it still shuts down after 30 mins of running. Fuel bowl is empty when it shuts down. I put a fan under the camper blowing the hot air from the generator away from the intake and wala, it runs fine then. The generator is getting vapor lock. It is sucking in the hot air from the discharge and recirculating it inside the generator compartment. It's getting so hot inside there it just vaporizes the fuel and shuts the generator down. This last time it did it I pulled the fuel line, broke the air lock, and it started right back up. I emailed GD to see what they have to say about it.

Did you have to install the vent on the underside of the generator, or did you just screw it to the bottom of the camper?

[msutoad]

Thanks for the note JKellerJr- I figure someone would say that, which makes me feel better that its supposed to work with the door closed. I just need to figure out if something is either not installed properly or if my genset is hosed up. Thanks again, and I look forward to some of your pics. Cheers-

The baffle screws with self tapping screws to a specific place on the genset itself actually. If you need detailed pics PM me and I can get you some!

Jason

[RoyBell]

The baffle screws with self tapping screws to a specific place on the genset itself actually. If you need detailed pics PM me and I can get you some!

Jason

Did you have to lift off the generator or were you able to attached it while still bolted to the camper?

[msutoad]

Did you have to lift off the generator or were you able to attached it while still bolted to the camper?

All is done with the genset securely in place!