Onan 5500 won’t stay running

[Hightowerng]

I have a 2008 Onan 5500 I just got the trailer used/as is from a reseller. When we looked at the trailer everything to be working and the generator was running. During our first trip we noticed a strong smell from the exhaust and at times running ruff. After the trip I went to service the system new oil filter and clean out the carb ect... I noticed the electric choke was disabled and the system was zip tied with the air valve on the intake about 95% closed. I took off the zip ties and and hooked the system back up and now the generator won’t stay running. If I hold the air valve almost closed it will run smooth but as soon as I let it open up it runs really ruff sputters and shuts down. I did a sea foam deep clean of the carb and replaced the fuel pump and filter and no change. Not sure what to do next new plugs maybe? Just need some help.

 

[hoefler]

Carburetor needs to be disassembled and cleaned or replace the caburetor

 

[6.7LMegaCab]

I had the same year/model. Take the carb apart (carefully so you don't damage the thin gasket) and use some thin wire to run through every orifice on the carb. I used a single wire from some cat5 cable. Blow air through it as well. That's what I did and it ran very well afterwards. If that doesn't work you may need a new carb.

Also if you don't know the history of those spark plugs, I would change them anyhow. A bad plug, oddly enough, can cause a magneto to go bad. That's what happened to my 2014 Onan 5500 that's in my Road Warrior. The entire generator had to be removed and the engine removed from the base just to change it. The generator only had 170 hours on it when the magneto went bad.

Once you get it running again, be sure to let us know what you did.

Sent from my SM-G955U1 using Tapatalk

 

[Lynn1130]

Before I would disassemble the carb I would be inclined to dump a bottle of Sea Foam into the tank and use the method you are using to start it and let it run for awhile. It will clean the lines and carb if you can get it to run. Tearing thing apart is always my last choice because almost always some part gets damage or lost or I end up running around town to find a part that broke while trying to fix it.

 

[dave10a]

Carburetor needs to be disassembled and cleaned or replace the caburetor

X2--- We make a lot of money servicing carburetors on marine and outboard engines because the owners do not properly store thier motors for winter or long term storage. To clean a carb properly it needs to be dissembled and cleaned with cold parts cleaner and compressed air to blow out the ports. Gasoline has at least 10% ethanol which absorbs water that in turn corrodes the internal parts. Proper cleaning is the only solution..

 

[LBR]

I brought our Onan back from the walking dead by siphoning out as much old gas from tank as possible, then put in a 5 gallons of fresh gas and 2 bottles of Seafoam for an IV shot.in.the.arm.

Ran it a few minutes each day for a couple weeks until it would continue to run, then more gas and another bottle of Seafoam with longer run time under increasingly heavier loads for another week.

3 weeks of pampering and close to 3 Seafoams later, runs perfectly....just as it did before our dealership "had to let our CY sit for parts" at their repair shop for 5 1/2 months...(Grrrrr)

Go to YouTube and search "Seafoam"...you will see the resurrection video specifically for the Onan.

 

[Lynn1130]

The other thing I don't see mentioned in your post is fresh gas in the tank. Are you still running on what was in the tank when you got it? The post above made me think of that and if you are trying to run on stale gas, it won't.

 

[b_king1]

X2--- We make a lot of money servicing carburetors on marine and outboard engines because the owners do not properly store thier motors for winter or long term storage. To clean a carb properly it needs to be dissembled and cleaned with cold parts cleaner and compressed air to blow out the ports. Gasoline has at least 10% ethanol which absorbs water that in turn corrodes the internal parts. Proper cleaning is the only solution..

Great advice! I concur