Onan 4000 Generator Problem

[Jerry_Amerson1]

Hey all,
I recently posted that the Onan 4000 on my Fleetwood was roaming and would only stay running if I wedged the Governor open, but that is not the case. I went out today to check the adjustment you all told me about and realized that what I was wedging wide open was the CHOKE!!
This puts a whole different twist on things and tells me that there is a fuel delivery problem. My first thought is to replace the fuel filter and I got the seafoam to run through it as well. I'm testing it without any load so if any of you have other suggestions I welcome hearing them. I will have to order the fuel filter so it will be next week before I get it replaced.

Any help is always greatly appreciated.
Thanks,
Jake

[Oldme]

OK so you have the opposite problem.
Not enough gas/ not rich enough.

Still could be the choke setting for altitude.

Or

Carb problem - Dirty jet, worn float valve/seat, or leaky float.
Solution is a carb rebuild kit or new/rebuilt carb.

The kit will have the new jet, float, float valve and gaskets, plus float gauge
and instructions.

Clean the carb before rebuilding with lacquer thinner and spray the internal passages with carb cleaner. Let dry before rebuilding.

30Min job after removal.

[Jerry_Amerson1]

I was wrong about having to wedge the choke open, I think I'm having to wedge the choke closed to get enough gas to the carb to keep it running. This just started on our last trip to the races, so I'm thinking it's a clogged fuel filter and I'm taking it out today and getting a new one.

I have also noticed that it looks like my GenSet is actually sitting in the compartment crooked, and it sways back and forth fairly easy. I don't know if it's supposed to be able to move around or not but it does so I have to check that out as well.

Any ideas on that would be appreciated.
Jake

[Oldme]

If you are able to keep it running by blocking the CHOKE OPEN then the choke is set too tight or ypu have a mechanical spring/lenkage problem. Just like cars of old you would need the choke to close more in colder weather than hot.

On the generator you will see an altitude setting screw. This does basically the same thing. Air is thinner at high altitudes.So you do not need the same amount of choke as at sea level.

Now you have have a problem with it either being set for the wrong altitude or
the spring/linkage that should allow the coke to open is stuck or something is broken. If the spring is broken then the air entering the carb will pull the choke closed and choke out the motor.

When ypu block it open, you are keeping the air entering the carb from pulling the choke closed.

[j-d]

There should be a tag or label on it someplace showing an exact Model and Spec Code. Might be a "BGE" - something.

[Jerry_Amerson1]

I'm looking at your picture of the unit and the one you show looks like it has the fuel filter right out front, and that's where my carb is located so it's different, but the same model.

[Jerry_Amerson1]

Yes, that's it exactly. The fuel pump and filter is over on the right at the bottom of the unit.

I know it has been changed because I have two receipts from Camper World where they changed it. It looks like they pulled a cover plate up and away far enough to pump mounting bolt, and it looks like there is only one. Then the connection to the fuel line is the next thing to undo, then I think they have put extra hose on the pump/filter so it can be pulled out of the unit before disconnecting the incoming line. I will also have to track down the hot lead on the pump so I can change it out as well.

Any help here would be greatly appreciated, and can you tell if that bowl on the carb comes off with the nut that's on the bottom of it.

Thanks again
Jake

[j-d]

Look like this?



If so, add 50-pounds or so to the 175 estimate above.

[Jerry_Amerson1]

I don't think it's the 4KY model. Mine has Onan 4000 GenSet as the model number.

It looks like dropping the unit is not what I want to do. If I can get to the fuel filter to change it out and then drop the bowl on the carb and clean it with cleaner that might do the trick.

The fuel filter looks to be down flat on the bottom panel at the rear of the unit, but I don't see any way to get to it so any suggestions would be appreciated. Also, there is a nut on the bottom of the carb bowl, so if I take it off can I just pull the bowl down and out for cleaning purposes.

Thanks again for your help.
Jake

[j-d]

You said ONAN 4000. Is the model number "4KY?" If so, I summarized carb removal above. You need to flex the blower housing a little. That's what the Torx T-30 screws are about. Then there's only 2 bolts, 1-mm hex heads, holding the carb and they're accessed after the air filter is off. No need to drop a 4KY to remove the carburetor.

If Model is NOT 4KY, then what is it, please...

[DrewE]

Jerry_Amerson wrote:

Has anyone ever pulled one of these carbs off with the generator still mounted in the coach, or should I go ahead and put a jack under it and drop it down.

If there's any chance of doing it without dropping the generator, attempt that. It's no fun to drop the generator--not particularly complicated, but a good bit of labor.

To drop it, one generally needs to disconnect the fuel line, the positive and ground DC connections, the remote start controls, and the AC connections, assuming the wires/hoses are not sufficiently long to reach the ground. If the fuel inlet for the generator is lower than the fuel tank, which is not at all uncommon, you would be well advised to get the fuel level in the tank below a quarter tank or so to avoid the possibility of siphoning it all onto the ground.

Disconnecting the AC lead, at least in my case, involves removing the voltage regulator/control modules (and hence also starter solenoid) from the generator to get to the ground and neutral connections, and also removing or at least partly removing the little control panel to get to the generator circuit breaker for the hot lead.

If you do end up dropping it, make some measurements first and if needed drive that side/end of your motorhome up on ramps so you have enough space under the skirting to get it out from underneath. A bit of planning ahead here will save a lot of aggravation. The generator weighs something like 175 pounds or so.

Don't ask me how I know this...and, on completely unrelated topic, be glad the starter motor doesn't need attention.

[Jerry_Amerson1]

It looks like I can get to the first two bolts holding the carb pretty easy, but I suspect there is a third around the back that may cause some problems. The fuel line looks easy as it's right in front. I really don't see anything else except the choke linkage and it's in back so I will need to get the carb loose before I can get to that.

Has anyone ever pulled one of these carbs off with the generator still mounted in the coach, or should I go ahead and put a jack under it and drop it down.

Also, where is going to be the best place to get a new or rebuilt carb.

Thanks again for all your help.
Jake

[WinMinnie02]

I would get it service and build a relationship with them. Buying a used RV has risks thus the lower price. I was fortunate to buy mine new 13 years ago and I take good care of it and make sure I used it. Thank goodness I did not listen to the person at the dealer who told me not to use the generator often.

[DaCrema]

If the generator ran fine prior to this and all of a sudden quit I would start by doing the simple things. The sea foam was a good start.

I would also consider the fuel filter replacement already suggested.

Have you check fuel flow by disconnecting the line from the carb and running RV? It should run long enough on the fuel in the float bowl to do the test.

The issue on my 2007 RV was the fuel pump. The replacement is involved but not that hard. Likely to cost less than a carb.

[mlts22]

With any used rig, especially with low generator hours, I'd just replace the carb first thing. Better that than trying to spend your time running random substances or do half measures.