Onan 5500 will not stay running.

timsitis

Member
Used my generator one time since I bought my 3850 in March and it quit after 20 minutes. Fuel pumping okay, oil okay. I am getting a code 1-12 on this which when looked up instructs me to go to the Onan dealer. Trying to save time with any known fixes or issues that you all may have. By the way, it fires up and shuts down within two seconds. If I manually hold the choke open along with the throttle, it will run for 15 seconds or so.
 

PUG

Pug
I had a 5500 in a 3950 I just sold and had kind of a similar experience. I always exercised my unit every 30 days and kept gas additive in it to keep the fuel from going bad. Also if you run ethanol gas it can plug up your carb but there is a ethanol additive to keep this from happening. One day my unit would start and then quit and start and quit. I cleaned the carb to no avail. Finally to it to a Cummins Onan dealer and they put a new carb in. Still not fixed. They pulled the unit out and found some kind of a spring clear down underneath it that had broken. They replaced that and presto it ran again.
 

TwoGypsies

Well-known member
It does sound like a fuel problem. The one thing I can offer is that ours acted like this with about 7 gallons in the tank, although I didn't get a code (actually, I don't know how to get or find a code...). I filled the tank and it immediately started and ran.
I need to take Pug's advice and get some additive and run it routinely.
 

Vtxkid

Well-known member
I agree that you should run the unit about once a month to keep it happy... Since you haven't run it since March. Get rid of the fuel and put fresh in the onboard tank... Ethanol has made it where the fuel needs to be replaced ever 3 months if you don't put in fuel additive to keep it from going bad.
 

timsitis

Member
It is gas and other then running it every month for a few minutes it ran fine to this point. It was a hot day and the gas was fresh as I had never topped the tank until then. I will get it to the dealer and see what they can find.
 

porthole

Retired
other then running it every month for a few minutes

This not the best way to "exercise" a genny.

Once a month is good, but you should let it warm up a few minutes, start adding loads up to at least half capacity, maybe 3/4 capacity. Let it run 15-20 minutes then remove all the loads and let it run unloaded for about 5 minutes.

Sta-bil in the fuel too. I add Sta-bil every time I add fuel to the tank, whether we are using it or not.
 
Last edited:

Wmnmy

Well-known member
I had the same problem mine kept cutting off I found out if I have a quarter tank of fuel it won't run filled it up and it ran like a champ in 110 weather it got hot so I opened the main door no problems since
 

neegirll

Member
I had the same thing happen... luckily an HVAC guy was camping next to me and looked at the wiring diagram and then looked at the unit... on the right side towards the back a wire came loose on the ride. It was a tight fit be he managed to get it hooked back on and it fired right up... saved me a trip.
 

newbie

Northern Virginia
Sounds like a fuel problem. You could make sure you are getting fuel to the carb. It could be a dirty fuel filter or a dirty carburetor.

John
 

gpshemi

Well-known member
Anyone know the model number for the Onan 5.5k in the 2010's? Mine's running after cleaning the green goo out of the bowl and carb, but it's running really rough.
It seems the common fix is to replace the carb...why do they not clean them? I took it apart. There's nothing shocking about it.
 

Vtxkid

Well-known member
Anyone know the model number for the Onan 5.5k in the 2010's? Mine's running after cleaning the green goo out of the bowl and carb, but it's running really rough.
It seems the common fix is to replace the carb...why do they not clean them? I took it apart. There's nothing shocking about it.
You should of recieved a Onan installation/ operating manual with your RV. That should have the information in it or tell you where to look for it on the unit it's self...
 
Top