Generator surges

Governor issue. Want to sound like a "pro"? The governor is "hunting". Proper governor action is an ideal point found between throttle reaction time and sensitivity to changes in load.

Governor induced hunting is diagnosed as steady speed unloaded all throttle positions (load must be disconnected and max speed-increase limited to 65 Hz) Steady speed until an "x" load is reached then the engine speed will oscillate up and then down, not down and then up. An analog Hz meter helps diagnose this. The vibrating reed type is the best. Have those also gone the way of the dinosaur?

I used to fix gumming issues with a cleaner called Berryman's Chemtool. Probably isn't the same stuff these days due to EPA. With engine not running I squirted it through the spray can straw onto governor and carburetor shafts with engine shut off. Moving the throttle back and forth by hand. Then I applied turbine oil or 3 in 1 oil for lube. Note the shut down engine notation repeat.

If the above did not work I then tore into the governor itself which is not recommended unless you are familiar with governors.

Boy, I'll bet Woodward gets a pretty penny for their electronic governors these days. They cost $500.00 33 years ago. Swapped out the power NPN transistor and driver on both of mine and they have trucked onward.

Here is what is going on now. I start the generator and it starts fine . I plug in a fan still runs fine. So no load or light load runs good. The wife plugged in the vacuum cleaner and it starts surging. The wife doesn't know any better so keeps running the vacuum and burns it up. Under no load the ac plugs are running 123v. I didn't check it when it was surging didn't want to burn something up.

I need to add I took the carb out cleaned it the fuel pump wasn't working so I pulled it out it was clean inside and so is the filter the plunger was stuck I freed it up oiled it and the pump works great. I was still having trouble getting it to pull fuel from the rigs fuel tank I fix that by replacing the rubber fuel line that was cracked. Before i id all that it would run but surge all the time and smoked black (rich) smoke. Now it runs clean (no smoke) and runs good under no load and light loads.

Seafoam is the best snake oil I have ever used. Spray/pour Seafoan into carb until it chokes out let it set for 20 mins then start the eng again, it will smoke like mad run it until smoke stops. Repeat this again and the smoking will diminish. Then put other half a can in a gallon of gas and run it until empty. Put the genset under load and you can see how much your genset burns per Hr. If this doesn't cure your surging then you can try more drastic measures.

My 6500 was surging under a load when I first got it. Someone (perhaps in this forum) suggested running a can of Seafoam mixed in a gallon of fuel through it. It worked great and hasn't surged since.

I know a lot of people think Seafoam is snake oil but it worked for me.

If your carburetor's clean and adjusted right: Replace the Governor Spring. Manual suggests that AFTER the messy project of cleaning out the "governor cup" but wife suggested I get a spring too, while going to Cummins/Onan for parts. I couldn't tell the difference between Old and New, but New solved it. Good Wife!

We Cant Wait wrote:
If it is surging without a load on it this is not uncommon.

I it surges under a load too.

If it is surging without a load on it this is not uncommon.

Our 96 Southwind also has the Onan 5500. It had a similar problem, surging.

Replacing the fuel filter solved my problem.
Maybe you will luck out and have an easy/cheap fix.

moved from technology