Onan 5500 won’t stay running

**joe2low** · 06-06-2023, 07:44 PM

Hello,
I have a 2022 Momentum 397 ths with a Onan 5500. It has around 45 hours on it and won’t stay running. I have replaced the fuel filter, and pump. With a new pump it will run longer but still won’t stay running. I have also try venting with opening the gas cap. That doesn’t seem to help. Any ideas? Thank you

**Redapple63** · 06-06-2023, 07:50 PM

Fist, Welcome to the forum! Sorry to hear of your generator troubles. I used to have the same genny. If this a propane or dual fuel model. I had a similar issue but it has far more hours and was a fuel pump issue.

These have governed on them to maintain a specific rpm to produce the required 60 htz which could also kept it from running (spring).

Some additional basic info fuel type and if your tank is in the rv or separate (sometimes the generators gat added and they may not have the built in tank.

Bill

**joe2low** · 06-06-2023, 07:59 PM

Thank you!
It is a gas gent with built in tank. Same set up as my previous fifthwheel.

**mwdilday** · 06-07-2023, 07:38 AM

I had a similar issue with mine. It was because I had the electric hot water heater on and it, along with other loads, was overloading the generator and shutting it off.

**msutoad** · 06-07-2023, 06:40 PM

I had a problem with my 2021 Momentum 381. It would not stay running, unless I left the front door open. I spent a ton of time debugging and working with Cummins, and low and behold there is a tornado action created with the air exchange from the Generator and the ground, so the cooling air was being sucked in from the hot air from underneath. GDRV send me a vent type baffle that screwed to the genset and it would push the hot cooling air to the side, versus just straight down. I have an entire post with pictures on this. If you search my username “msutoad” you can find the genset post about my issue and the remedy with the pics. Hope this helps

**joe2low** · 06-22-2023, 02:10 PM

Originally Posted by msutoad

I had a problem with my 2021 Momentum 381. It would not stay running, unless I left the front door open. I spent a ton of time debugging and working with Cummins, and low and behold there is a tornado action created with the air exchange from the Generator and the ground, so the cooling air was being sucked in from the hot air from underneath. GDRV send me a vent type baffle that screwed to the genset and it would push the hot cooling air to the side, versus just straight down. I have an entire post with pictures on this. If you search my username “msutoad” you can find the genset post about my issue and the remedy with the pics. Hope this helps

Thank you for the info! I have ordered the part. Hopefully this will fix the problem. Kind of frustrating looking further into it knowing it's a known problem from at least 2017 - on. Several different version depending on how it's mounted.

**joe2low** · 07-10-2023, 06:35 PM

Looks like GD pre installed the exhaust diverter. Have replaced 3 fuel pumps, 2 filters, and will replace not stay running with the front panel off. It is still getting too hot with it all closed up. Any one else have any ideas.

**Redapple63** · 07-10-2023, 08:14 PM

Originally Posted by joe2low

Looks like GD pre installed the exhaust diverter. Have replaced 3 fuel pumps, 2 filters, and will replace not stay running with the front panel off. It is still getting too hot with it all closed up. Any one else have any ideas.

What about the fuel filter? From the fuel line to the carb? Blocked or collapsed fuel line?

Just throwing stuff out there, hopefully something sticks.

Bill

**tjndsa** · 07-11-2023, 09:23 AM

Following thread as we occasionally have a similar issue. Have checked fuel lines, fuel pump, and fuel filter. All are in great running order. Through research, learned that sometimes the level of the oil can be an issue as the 'full' line on the dip stick is not in the correct position. Generac knows this and has not corrected it. When oil heats/foams up, it reaches the sensor and shuts it down. Also learned that if the generator itself is unlevel within the compartment, that can be an issue as well. Interesting that having the water heater on might be an issue too. As of today, it seems to be running ok during monthly start ups.