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edge68474 · 07-18-2019, 06:55 AM

A couple of days ago I went out to the MH to run the generator like I do about every month. After about 20 to 30 minutes, it stopped. OOOk. I remembered seeing or reading about the oil level and lowering the level to make the generator run. I took some out with a turkey baster, not very much, and by the time I got around to restarting the Gen, a little time had gone by. I restarted and again, after about 30 minutes it quit.
That evening I went online doing some research and ran across that video on lowering the oil level. They mention taking out enough but keeping it between the add and full mark. Next day I take it down to almost the add mark. Started the generator, let it run 30 to 45 minutes, it's still running ok, so I turned on the AC and let all run for about another 30 minutes.
Well, it did keep running until I shut it down. This seems so weird to me. I haven't had to remove oil before this. I did check the oil level after shutdown just to see and due to expansion it did come up some.
I hope that solves the problem cause I was thinking I would have to take it to a tech to see what is going on, maybe I still do before the winter run south.
I read where this happens to a few different models not just the 4K.
I have a bout 132 hours on the generator right now and when I bought the MH I think it only had about 50 hours.
I am using 30 wt oil as recommended for the season around here. I wonder if changing to 10-30 or something would make a difference, I'm thinking not.
Other than doing the maintenance on this, what else can a person do to make sure it will run when you need it? Can the techs hook into the system and diagnose these Onans?
What are your thoughts on the oil level thing?, and, has Onan done anything about it. I really don't like to run it so close to the ADD mark. On any motor I have really. I like to keep them full.
Your thoughts gang, Thank you.

stew1 · 07-18-2019, 07:04 AM

Mine was doing this but would run forever under load then die a few mins after the load was removed , replaced carburetor no problems since

ThePowells · 07-18-2019, 08:57 AM

Unfortunately the Onan default for "everything else" is the normal. Service ours and ran it for 30 under load and it died. Ran in "fuel starvation" mode and would die. This was the hottest day of the year, so far. Two days later when I came home, it ran fine all the way home, so it wasn't oil level. My next step will be a new Airtex fuel pump and filter. It's kind of a toss up between oil level and fuel delivery system.

edge68474 · 07-18-2019, 09:05 AM

Thanks for your replies.
I just went out and started it up again and will let it run for awhile. I checked the oil level and it was at full mark. I'm thinking it holds oil up top for some time, maybe. Further diagnostics on my part.
What I am wondering about is how it keeps itself cool for any length of time especially when it's hot out.
Mine is gas just to let you know. I am going to let it run about 2 hours this time.
Have a Great Day

Teamfoxy · 07-18-2019, 09:54 AM

Quote:

Originally Posted by edge68474

Thanks for your replies.
I just went out and started it up again and will let it run for awhile. I checked the oil level and it was at full mark. I'm thinking it holds oil up top for some time, maybe. Further diagnostics on my part.
What I am wondering about is how it keeps itself cool for any length of time especially when it's hot out.
Mine is gas just to let you know. I am going to let it run about 2 hours this time.
Have a Great Day

Very likely the oil level has nothing to do with it. I have seen that video and lowering the oil level did nothing for me.

In hot weather, older fuel pumps on the 4k Onans stop working because the rubber parts bind up. When the generator cools down again it will run for another 30-45 minutes. One can also get a vapor lock in the fuel line if the area between the generator and its housing gets dirty enough to slow the air flow.

So the first step is make sure that the inside of the generator housing is clean. I use one of those skinny long brushes made for cleaning dryer vents. If the generator still shuts down, immediately pull the fuel hose off the carbureator and press the prime button. If you don't get fuel flow, the pump needs replacing. Very likely the pump will work fine again once it cools down, but it will fail again when it gets hot.

Replacing the fuel pump on a 4k is kind of a pain because it is buried behind the control module and that needs to come out to reach the pump. There are some U-tube videos that show you what is involved. When you replace the pump, put a new fuel filter in as well. I had to do this with my 4k last year and it ran like a top after that. Have since traded coaches and have the 5.5 Onan, which I like better.

edge68474 · 07-18-2019, 09:08 PM

I checked for fuel flow after fighting to get the clamp off of the hose. Never seen a clamp like that one. That was after it shut down again. Flow seemed good to me. I see sponge like material around the left side and towards the back. Is that for insulation or is it also for air filtration. There is a fan of sorts in that area also. I had to use a mirror to see it move. Maybe that is a fan for cooling??
I'm thinking I should blow some air in there and try to clean it up some, yes, no?? Airtex fuel pump and filter is mentioned. Does that mean that one doesn't have to have a pump from Onan, and, is it better??
Thanks again. Much appreciated.

ThePowells · 07-18-2019, 10:10 PM

Many have went to the Airtex, and that is what I'm going to. I just wish I already had it since the heat index will be about 115 tomorrow afternoon. Sounds like a perfect day to test a fuel pump.

edge68474 · 07-19-2019, 04:18 AM

Heat relief is in sight for you folks.
Thinking here with a question on heat. Is it common for generators, Onan in this case, to shut down when it gets HOT out?
I guess I need to see the fuel pump to understand rubber parts binding with heat.
And of course, things fail when you need them the most.

edge68474 · 09-13-2019, 07:51 PM

The mystery continues. Today I started it up, after a bit turned on the AC. Let the AC run for about a half hour. Let the Gen run for an hour. No problems. I will try it one more time before the winter trip. I guess if I have problems on the road I will just find someone to try and fix it. Still makes me wonder about outside temperature. Last time when it quit it was pretty warm out. Today is kind of cool. But when it's hot and your not connected to power that's when you definatley want the Gen to work in order to run the AC. My words now, OH WELL.

rfkurtz · 09-15-2019, 05:47 PM

Mine shut off when I was working at the storage place. It is stored outside and the A/C was running. The slide was not out and it was in the high 90's with the sun beating down on the side. I opened the hatch, let it cool down and started it after about 20 minutes. Ran ok.

Looked at manual and it stated that it shuts down on high temperature.

Corc · 09-15-2019, 09:05 PM

The 4000 Onan is air cooled and doesn’t have a temperature shutdown. Temp shutdowns are usually due to boiling the fuel. Cool air comes in the front out the bottom. Got to make sure the front is getting cool air and not recirculating the hot air. Do not take the door off when running, it routes the air.

danhannah · 09-16-2019, 02:48 AM

On my Onan 4000, the oil MUST BE just touching the bottom of the dipstick. Otherwise, it foams up and somehow kills the generator.

I always keep my vehicle oil filled, like you, but don't worry, there is still plenty of oil in the crankcase. The proof is, yours runs great with less oil.

The dipsticks were built wrong, on at least some models...

edge68474 · 09-16-2019, 09:03 AM

Thank you for your responses, much appreciated. Guess I will just roll with it and see what happens. Maybe I will run it again today and see what happens. It's cool out again. I think summer is gone now, BUT, winter is coming, Yeahhhhh!!. That means head south.

HighDesert · 09-16-2019, 10:05 AM

This is not just a Onan 4000 problem. I am having the same thing happen on my QG7000 Onan. First thought was fuel pump - nope, works fine. Have the carb adjusted for elevation I am at (3000'). Last trip out, fired it up - rand fine for 10 - 15 minutes, then just shut down - like flipping a switch. After letting it cool down for about an hour - ran fine for the next 5 days. Go figure?? I am going to take the MH into a local authorized Onan service center in Bend after this next trip I have and let them sort it out as there is smelling going on I cant find. I just changed oil and filter with 82 hours on the unit. BTW - cranked and ran fine.