The sweet sound of generator surging

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Jun 2, 2006
I just bought a 89 fleetwood southwind. The generator starts up fine and idles good for a few minutes. After it warms up it starts its surging sound. If I turn on the AC or the microwave it stops surging and everything is fine. I have done some searches on the web and I have come to the conclusion that I need to change the fuel filter and take off the fuel line and put it in a gas can with fuel injector cleaner in it and run it with a load. Do you guys have any other tips?
Before you do that check to see if there is an altidute adjustment on the side of the generator and if it's set properly

Also, look up the genset's owner's manual In another thread I posted a link to ONAN's site where you can download manuals for most anything.  Sounds to me like a minor mal-adjustment but I'd need to be hands on to be sure

The genset governor is seeking to maintain a constant rpm. It's probably a centrifugal and spring system, and over time the spring may have become a little weak and it's overrunning a bit; therefore the hunting. At higher loads, it's not an issue because the genset has its' 'foot' constantly on the gas to maintain the required 1800 or 3600 rpm. My suggestion would be to drain and change oil and filter, a new fuel and air filter, new spark plugs, carb rebuild, new governor spring, and proper adjustment of all components. It's an old unit, and deserves a little TLC. You didn't mention what brand/model unit it is, but some have an articulated arm coming from the governor which you could try adjusting a bit to overcome the problem temporarily. It's a little tricky without an tachometer or freq. meter, but can be done if you're careful. 
Thanks guys. Its a Onan 6.5 NHE. It probably has not been used for a year before I got it. I had to actually disconnect the fuel line and put it in a gas can to prime it to start. Now it starts great hooked up to the gas tank on the MOHO but like I said, its surging until I put a big load on it like a air conditioner or microwave. It does have the altitude adjustment. I looked in the manual and it did not mention how to adjust. What do I do? Do I just warm it up and then adjust until it stops surging?
The altitude adjustment will not stop the surging; it's there to adjust the fuel/air ratio for different altitudes. Simply set it for your approximate current altitude. The other things I suggested will probably stop the surging, in particular, the governor spring and setting.

Also, run it under heavy load like the a/c for at least an hour. Gensets should be exercised this way for about 30 minutes each month to keep them running properly. Obviously this hasn't been done.
I wanted to just post a follow up for anyone that has had the same problem. I spoke to an expert yesterday when I purchased all my " tune-up " parts which in the end I did not need except the oil filter and oil, but good to have this stuff laying around.

He gave me a few tips.
-Turn the fuel mixture out counter clockwise. You cant go to far because there is a cover on the screw keeping this from being a problem. ( This actually fixed the problem for me and now it purs like a kitten )
-Remove the clip on the carb that the governer connects to and crush it down with plyers. Sometimes these have slack in them creating this problem.
- Move the condensor out of the points box and mount near the coil. There is a screw rigt there that you can remove and mount the condensor. The condensors tend to heat up in the stock location creating a problem thats tough to trouble shoot.
- The governer spring is generally never a problem unless your unit is super old or the spring has been damaged. You can pretty much tell by tugging on the arm while the engine is off to feel the tension.
Hey guys,

While you are on this subject my Onan generator runs great until I turn on my a/c.

Once I put a load on it the thing starts cutting out.?
Normally this only happens during the hot part of the day.

Mornings and late evenings the generator seems to run just fine with the a/c on.

I had new plug, points and condenser installed but I am still with the same problem
Any suggestions???

Robert Skinner
I am for sure not the expert but I would think thats a carb problem. Either in need of a cleaning or adjustment. I was told you can take the fuel mixture screw cap off and turn it 1/2 half turn either way and put the cap back on if you need more adjustment. Make sure too with a multimeter your outlets read around 120v too when you adjust.

My best suggestion to do is get on the manufacturers website and find a authorized repair center and call them explaining the problem. The guy I went to see even showed me what to do on generators that were in his shop. Very helpful guy!

Sounds like it's not getting enough fuel, but why only when it's hot? Is there adequate air flow in the generator compartment? Maybe you're getting vapor lock. As QSL said, carb. problem or fuel filter clogged, maybe float or needle valve that it operates, but that shouldn't be temperature dependent. Are you getting any black smoke from the exhaust? - possible choke problem. 
Is it possible that the fuel line? from the fuel tank has a rubber hose ( eliminates vibration) may have deteriorated on the inside and be collapsing when the suction starts.? ? It would normally be about a foot or so from the fuel tank.? Just a thought? ?cause this has happened to me before.
QSL said:
He gave me a few tips.
-Turn the fuel mixture out counter clockwise. You cant go to far because there is a cover on the screw keeping this from being a problem. ( This actually fixed the problem for me and now it purs like a kitten )

Interesting.... I'd have thought it woudl need to be turned the other way... Glad you got it fixed though  Good job

Hey everyone,

Thanks for the advice. Here are my comments

It looks to me like the rubber hose leads all thee way from the tank to th generator. 
It does look old how do I tell if this could be the problem??

Yes we tested the voltage when the generator is running normal and it is 120 volts.

It looks like the generator has plenty of breathing room.

No smoke coming from the exhaust that I can see.

What is the manufactures website address, where I can look up a local repair shop.

I haven't been able to find anyone willing to work on a Onan near me yet??
Onan is part of Cummins so look for a local Cummins shop.  Many of them also are Onan repair centers.

use this to find a service center.
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