I am not an expert by any stretch of the imagination, but I have a good friend who lives near me, who has worked on them for years. He is retired and is always willing to answer my questions about my two Onans. Post your problem, and I will ask him. Others may learn from the answer.
Well to start off, it is a 98 Onan Emerald 5.5 BGMFA26105H 120V, in a 99 H/R Vacationer F53 chassis
We use the gen while traveling, to run the a/c unit or units in hot weather.
During our travels & the gen running, if a real hard bump is hit in the road, it will shut the gen down.
I've ran the gen with both a/cs on & the fridge on ac & it does just fine until a hard bump is hit.
Even had just one a/c on, fridge on LP gas & nothing else on ac except the 12v converter, thinking it may have to much load on it & still after a hard bump will cut the gen off.
The other week, on our trip out to SD & back, it cut off three different times while stopped taking breaks. Once going out & two times coming back home.
It was hot out, so I was thinking it must have been high temps in the gen compartment causing it to shut down. Last time it did it, I used a temp gun & temps inside the gen area were around 190~200*. The one cylinder head you can see, the temp gun was reading 210* on that head right after the gen shut down.
Once it shuts down while stopped, after a little cooling time it with start back up, but trying before it cools it wont start.
Could it be the fuel pump is getting so hot it is vapor locking or so hot the pump is locking up.
Oddly, it will shut down instantly just like as if the switch was cut off.
Most normal small engines, if it has a fuel problem, it will have a flutter like hesitation before cutting off, but not this gen so I'm inclined to think something with the gen part of ignition system.
Now I'm just guessing on this, is there a low oil shut down on the inside of the engine block like other small engines have, or is that controled by the oil pressure sending unit.
What is realy odd, the 89 GBM we had before this 99 H/R, had a 6500 Onan Emerald & it would shut down just like this one when a hard bump in the road was hit.
I'm out of clues trying to figure this out, I change the oil & filter just after every long trip when back at home, like if we have to run it several days & I've replaced the oil pressure sender, installed new spark plugs & the air filters fairly new.
Dont know if any of you ever heard this before, but was told some years ago, if you drop a gen to hard, like unloading it from a pickup, you can knock the ac current out of it. Was never told what that ment & was told by two different people, but it sure sounds crazy to me so I'm wondering.
I called my "expert" friend and told him your problem. He said it would probably be one of two different things: low oil pressure sensor or the remote stop switch. You said the oil was OK, so it probably is the switch. He said it is the cut-off switch on the box at the generator. If you open the box, check to see if there is a loose wire close enough to the off switch to make contact with it when jolted from a bump in the road. He has found this to be a problem is some models. Let us know.
I also have a Holiday Rambler that has had the same issue. See my previous post below...Very few on this forum will say you could have a vapor lock issue but I really believe that is what is going on. Mine will run in the driveway here in Texas all day in 100 degree heat with no problem and die six hours into a 1000 mile run in August.
Read the post, not sure what the fix is other than maybe adding some additional air flow when moving. I think with the chassis and gen exhaust temps added to the outside temp and road temp is what is causing my issue.
I have had the same issues on a 2000 Onan 5500. Original run and die problem ended up being a fuel line issue. Replaced the complete line and all my problems went away except....last August when the temps were 100 plus+ on the road it died after about 6 hours of constant running. Let it cool off for an hour or so and it was good to go for another hour or two. This happened 2 days in a row in the high heat, but has not happened again. I have run 5 or 6 times under full load for 4 to 5 hours each in cooler weather with no problems. Oil level has always been correct in my case. I really think there is a vapor lock problem in the high heat conditions. I think that is why the fuel line was segmented in several places with metal tubing instead of fuel hose running the entire distance to the tank. I was unable to solve my original problem going back with the existing metal and new rubber fuel lines. I think I had a small leak in the one of the metal sections. I will be making another 2200 mile run from Texas to Tennessee in August so I will let you know if I come up with anything else.
Hope this can help in some way. I am thinking of adding additional sheet metal to move a little more air. I am going to wait until after this upcoming trip see if it shuts off.
Ok, thanks for those idea.
Now on the oil level, do you check the level with the cap screwed in, or just place it in the hole & not screwed in.
Not screwed in is how I normally check the level, just like on a lawn mower.