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Hi folks, I'm having an issue with my home generator surging and pulsing.

Its a coleman 5000 with a 10hp Techumseh engine. I bought this unit used about three years ago with a dirty carb. I took it apart and cleaned the carb, ran a tank of good gas with extra carb cleaner through it and it began running great. I've used it 4 or 5 times in the past three years and it always starts easy and runs smooth. I always add a bit of carb cleaner and Stab-IL as well as a drop or two of Lucas Oil to every tank of gas.. I do this for all my small engines around here as it has greatly reduced maintenance issues on everything from the chainsaws and log splitter to the mower and leaf vacuum. (that ethanol is a pain in the rear!)

This past weekend, we had a big windstorm in Michigan and we lost power while the temps dropped into the low teens and some single digits. The generator ran fine for a while, then started acting up. It is pulsing.. When it first started doing it, I was able to close the choke lever just one notch from wide open and it fixed the problem. Then the problem slowly returned. Research on web almost always blames the carb..

I had an emergency new spare carb on the shelf just for this generator. No change.. generator still pulsing. (It was a lot of fun replacing it in the dark, at 10 degree's F last night) I noticed that if I place my finger on the governor linkage and sort of stop it from oscillating every second or so, it will steady out and run smooth for 20 or 30 seconds when I take my finger off..

I also tried adjusting the idler screw so it could not idle below 125 volts @ 62hz. (I have a fluke meter to measure this stuff) Adjusting the idler screw seems to have helped but it is causing the generator to idle higher than it should under no-load and it still want to pulse sometimes.

The generator seems to also run smooth if I turn some appliances on and place it under load. When I turn on the toaster, the output voltage drops to 110 volts and 59hz.

Something else I found odd... The pull cord to start the engine is unusually hard to pull.. I am almost certain this is because of the extremely cold oil as it gets easier to pull the start cord once its warmed up. It only takes two pulls to cold start the engine at 12 degrees.

As I spent 14 hours messing with this thing on and off, it seems to me that it was giving me more problems as the night wore on and the daytime temps of 24 deg dropped to nighttime temps of around 10 degrees. Anyone ever hear of temps affecting a generator? All help is appreciated. Thanks!
 

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Discussion Starter #2
For some reason, my neatly organized paragraphs got deleted and reformatted into one big long one.

sorry about that.
 

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Have you considered the carburetor icing up?

You describe it almost perfectly, runs fine for a while then acts up. If you shut it down and restart it, does it run good at first? Usually, residual engine heat will help melt any ice - if it gets warm enough for it to happen.

If it was a dirty carb it should do it all the time.

Maybe you can make something to help warm the air before going into the carb, like what a snowblower uses. You probably don't need the air filter in winter.
 

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For some reason, my neatly organized paragraphs got deleted and reformatted into one big long one.

sorry about that.

Fixed the best I could for ya!


My Coleman genny is a B&S and it has a deflecter so it draws in warm air off the engine.... No help to me because if my power goes out its in the middle of a hurricane in the summer

My B&S genny does not have this pre warmer

The Onan on the motorhome has a pre warmer too

The tech may not run right without a air filter, the tech on a go-kart I had would surge and barely idle w/o the air filter so maybe check out your air filter

If its got alot of hours the governer can be wore out

If it is iceing try the idea in the link I posted, it should keep the genny warmer

http://www.powerequipmentforum.com/forum/9-generator-forum/76-good-cheap-way-quite-your-gen-set.html
 

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Discussion Starter #5
Wanted to give you all an update on this... It would appear that the cold weather was causing the problem.. Looks like gasoline doesn't vaporize very well when its 10deg outside. Is that considered "carb icing" ?? Sure seems like it to me. To solve the problem, I build a quick plywood box around the generator with the air intake on the generator head side so that the air would have to flow past the cylinder head, pick up heat from it, then enter the carb. It worked great and it stopped sputtering almost immediately when I put the box over the generator. To make a long story short, I have changed the generator over to use natural gas from my home when the power goes out. I plumbed a gas line to the outside of the home with a cap and valve and can now hook the generator up to it anytime. In the sub-zero temperatures, the generator runs smooth as can be on natural gas.. its absolutely amazing how smooth it runs.
 
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