Onan 2800 S2 Disable But Still Stops

[booster]

Originally Posted by nomadikus

So far the parts have been available on the Onan site (rods and valves). I don't trust myself with the engine internals yet so I'm waiting for a friend to come by and check things out with me. He did say that the rocker arm seemed like it had more play than it should, and the rods seemed to fall out kind of easily, even after we straightened them. I did just do a compression test and I'm only seeing 32 psi as it cranks (from the starter motor attempting ignition), so it looks like we're probably opening it up to see what's going on.

I have never seen the valvetrain on an Onan, but usually there is some kind of lash adjustment and a quite tight specification for setting them. I recently adjusted the lash on our 20+ year old John Deere yard tractor with a Kawasaki engine and the setting was quite tight . IIRC it was in the range of .002 to .004 clearance and a PITA to set because of the weird double threaded support you adjust with all 3 of your hands. Even that tight clearance feels really loose sometimes on the tiny rocker arms.



It will be interesting to see what you find inside the top of the engine. I hope with head off you can see down to check the condition of the lifters and cam to make sure the pushrod didn't mark them up.

[Stovebags]

I've had the same issue with only running when holding the start button. Went underneath and unbolted the rubber hose line at back of gen. It's like some kind of water waste line that gets clogged. Bent it and reamed it out with a wire. Started fine after that. Done that maybe 3 times. Maybe you have already done this but if not it's worth a try...
r

[honeyboy]

I am, by no means an expert on your Onan issue but, this same thing happened to me. After $800, the generator repair weasels found that one of the brushes was totally worn out on one side. One was fine and one was totally worn down. They replaced the brushes and it’s been fine since. I have no idea why worn brushes would cause the “ only run when holding the button” condition but, replacing the brushes fixed it.

[nomadikus]

Huh, that's interesting. The only hose on the back of mine is the fuel line coming in. It does make sense that it might varnish up I guess, if fuel sat long enough in it. I seem to have a pretty serious compression problem so we're going to take the engine apart and see if anything is obviously out of tolerance.

Originally Posted by Stovebags

I've had the same issue with only running when holding the start button. Went underneath and unbolted the rubber hose line at back of gen. It's like some kind of water waste line that gets clogged. Bent it and reamed it out with a wire. Started fine after that. Done that maybe 3 times. Maybe you have already done this but if not it's worth a try...
r

[booster]

Originally Posted by Stovebags

I've had the same issue with only running when holding the start button. Went underneath and unbolted the rubber hose line at back of gen. It's like some kind of water waste line that gets clogged. Bent it and reamed it out with a wire. Started fine after that. Done that maybe 3 times. Maybe you have already done this but if not it's worth a try...
r

I think that is atmospheric reference hose for the regulator on propane generators.


Is your generator propane?

[nomadikus]

That's interesting - I think that would be a voltage shutdown. From my reading I think some of them shut down when the wrong voltage is appearing on the 110 out to protect your in-coach equipment. Good thing to add to the list of problems given it doesn't seem like it's the S2 sensor.

Originally Posted by honeyboy

I am, by no means an expert on your Onan issue but, this same thing happened to me. After $800, the generator repair weasels found that one of the brushes was totally worn out on one side. One was fine and one was totally worn down. They replaced the brushes and it’s been fine since. I have no idea why worn brushes would cause the “ only run when holding the button” condition but, replacing the brushes fixed it.

[Stovebags]

yes, an Onan gen on a 2012 Roadtrek

[nomadikus]

I put together a 7 minute video just going over the Onan inputs and outputs for those who are considering tackling fixing their generator themselves. Includes the location of the S2 sensor (from the top). It isn't super dense, more meant to bridge the gap I had with the videos I'd seen, especially with how many inputs and outputs the gennie has. Hope it's helpful to somebody.

https://www.youtube.com/watch?v=t4MP0aI2FNc

[Andiamo RV]

My 2800I had the same issue in June. Took my 2022 Winnebago Travato 59K to my local Cummins dealer and they looked at the error code (flashing lights on start buttons directly on the device underneath my rig) and It was two flashes and then eight flashes. Error code 28. Except, there is no error 28. It was 82! So they took it in and did some diagnostics on it. Turns out I have a bad pressure sensor on the fuel injection system. Its Nov. 3rd now and I'm still waiting on that part to arrive. They told me at the time there were none in N. America and it would be months... I hope your situation is better. Check the error codes. Or drive it to a Cummins repair shop. Mine is covered under warranty... if they ever get the parts.