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dieselclacker · 10-19-2021, 05:55 AM

Try Amazon for carb. They have kits, or you can get new knock off carburetor for your Onan for less than $60.

yeloduster · 10-19-2021, 07:31 AM

The carburetor on the 4K Onan generator on my old Bounder started acting up probably due to lack of exercise. I bought THIS and a repair kit which is mostly gaskets.

I think the carburetor on your generator is essentially the same design as my old generator.

I disassembled the carb, dunked it in the carb cleaner for a few hours, rinsed it thoroughly with water, used an air gun to blow off the excessive water and let the parts set in the sun for a day. I re-assembled carburetor and it worked fine for the rest of the time I owned it.

SmilingSam · 10-19-2021, 06:39 PM

Of course make sure all levers and arms on carb work freely and seemingly correctly then:

I would suggest try cleaning carb with a high quality carb cleaner, onan makes them but any good brand should help - you are trying to remove any gunk (dried gas & blow back) that may hinder carb.

You spray directly into carb air inlet, the gen will likely almost quit, of course stop spraying, do this several times, then the directions say to spray a massive amount until gen dies, let it soak in and dry some 10mins? and then restart and do again a few times - then I would always spray massive amount and just let sit overnight.

my old onan bgm 5000 would need this nearly every yr, as preventative if for no other reason - when you need a gen, that is NOT the time to get it working well !!

GL!

ps: if above does not help/work, do the carb rebuild bit.

Quote:

Originally Posted by CamJam1

DieselClacker, I'm very familiar with what you did as I was previously reading your old posts. In fact, yesterday I did more or less the same thing, but I instead ran a hose through the unused vent port on the passenger side of the tank. As it turns out that did not fix my problem, but at least I now know that it's not a fuel pick up or pump problem.

I spent today working on it and discovered that if I hold the choke partially closed that the generator does not shut down. I think that means that the mixture is too lean, which COULD be a restriction in the fuel line or a pump that is weak, but since I've changed 95% of the fuel line and tried three different pumps, I think it's more likely that the carburetor itself is the problem. Could be a vacuum leak too, I suppose, but I'm going to go after the carburetor first as these small engines with carbs are notorious for such problems when they don't get run a lot.

On the way home I stopped by my local RV dealer to see if they could clean and/or rebuild the carburetor for me. They said they're not allowed to do that any longer. Not sure if that's due to regulations or just a corporate decision, but they will only replace the carburetor now, which is $400 not including installation labor. The service manager suggested I just buy a rebuild kit and do it myself. I might do that, but I really hate working on carbs.

Tom, thanks for your tips on dealing with the fuel tank when replacing the generator fuel line. I'll keep that in mind in case i decide to go back to using the factory fuel pick-up.

CamJam1 · 10-20-2021, 12:17 PM

After trying to clean the old Onan carb and getting nowhere, I went ahead and ordered a knock-off carb from Amazon. We'll see how that goes.

GREGORYJ · 10-21-2021, 09:52 AM

Hi Camjam1, I also had this similar problem with my Onan 7000 and was also convinced it stopping after a few minutes, especially when the load of the AC kicked, it was a carb or carb vacuum problem. I could keep it running by manually holding the choke at a particular position. I replaced vacuum choke control and hoses, cleaned the carb , and none of these things helped. After searching on Google, I found another owner mentioned a problem with one cylinder not working. I started the generator , nursed the choke to keep it running, then let it stop and felt each cylinder rocker cover and found one cylinder was cool, the other hot. I removed the rocker cover on the cool cylinder and found the intake valve rocker was broken, so that cylinder was not working at all. It appeared over time the adjustment stud the rocker pivots on had worked loose and slowly rotated out to a point the rocker maybe badly mis-alingnment and broke. The exhaust rocker stud was also loose and had rotated out as well. I replaced the broken rocker($20) & adjusted both, the generator engine ran perfect from then on. I was very surprised how well the generator run on one cylinder when playing with the chock to get it running until a load was added, like the AC, when it usually died. Yours may not have this fault, but it easy to confirm, feel each rocker cover after it runs for a few minutes. The Onan 7000 & 5500 are very similar. Yes, we sure have drifted away from talking about suspensions.....LOL.