[updated:LAST EDITED ON 01-17-03 AT 01:01 PM (EST)]I have a Generac generator (5Kw w/10 hp Briggs and Straton engine).

After running continuiously for 6-7 hrs, the engine started pulsing or surging. At first it was barely noticable but got worse over 15 minutes or so until it was very apparent. At this point, the output voltage was affected (lights started dimming/brightening in time with the surges).

I shut it off for about 10 minutes and restarted it (started on the 1st pull) and it ran fine for about 10 minutes and started doing it again - barely noticeable at first, slowly building in intensity.

Turned it off for another 5 minutes and restarted it (again on the 1st pull) and after a couple of minutes it started again - same as before, almost imperceptible at first getting gradually worse until it was a problem.

Anyone have any idea what might be causing this?

Your thoughts and assistance on this is greatly appreciated!!!

Gary M.

White '02 F250SD SC SB Lariat 4x4 v10 3.73LS Auto Offrd & Cmpr Pkg, Man Hubs/Xfer, Bed Rails, Mud Flaps, Vent Visors, CB

White '02 Ranger 4x2 3.0L XLT 2dr SC vent visors, camper shell

 

Does it have a fuel filter that might be plugged? That sounds like it's a governor surge and an insufficent supply of fuel could cause it.

It also could be a low level oil switch, oil level drops off and the switch cuts power to the engine, oil level raises as the engine slows down and then the switch kicks back in.

It also could just be the carb needing adjustment.

 

I have 2 generaters like you have and have experianced that too. adjust the carb a little and it should smooth out.

 

Don't be afraid to contact Generac- they're gret to deal with. I had some minor problem with one of their new units, they sent me a new part and a fitted nylon cover for it- at no charge!

 

Thanks for the quick replies!!! This is one great site!

Gary M.

White '02 F250SD SC SB Lariat 4x4 v10 3.73LS Auto Offrd & Cmpr Pkg, Man Hubs/Xfer, Bed Rails, Mud Flaps, Vent Visors, CB

White '02 Ranger 4x2 3.0L XLT 2dr SC vent visors, camper shell

 

i would just about gaurantee the carb needs adjusting. try that.

 

One other thing I have found with many of my small engines, especially those that don't get run all the time...

The fuel sometimes gums up the carb and or the float bowl. Often if adjustments don't work, a good carb cleaning will fix it right up. A good carb spray shot into all the likely places, nooks, crannies, small passages, jets etc will usually do it.

The carb on most small engines is pretty simple.

Good Luck,

Jim Henderson

 

I know this is an ancient thread, but since it bumped up to the top, I thought I'd throw my two cents in.

Always check the easiest thing first: fuel filter. While likely not the culprit, it could be.

The phenomenon described is called "hunting and surging" in the small engine world. It can either be governor-related or carburetor related. It more often is carburetor-related in these days of ethanol fuel.
The engine "runs out" of fuel and the governor opens the throttle to provide more. The fuel supply exceeds the need and the governor relaxes. The carb runs out of fuel again. Rinse and repeat over and over.
There are two fuel circuits in your carburetor; that of the main or high-speed circuit and that of the idle fuel circuit. Unknown to many, during normal low- or no-load operation the idle fuel circuit is adequate to the needs of the engine. The high-speed circuit will kick-in and provide fuel when the engine comes under load. Hence the deepening of the engine note when you demand power from your generator (pull the trigger on your 10 amp circular saw, for example).
The governor is responsible for maintaining the rpm of the engine regardless of the load applied to the engine. So, when you turn on your saw, the rpms drop, the governor spring pulls the throttle open against the governor speed sensing device inside the engine and enough fuel is provided to bring the rpm up to desired while the load is being applied. Turning off the load will allow engine rpm to increase and inform the speed sensing device to push the throttle closed a little bit to again reach desired rpm.

All of this rather lengthy explanation means that you very likely have an obstructed idle fuel passage. In the old days, with fully adjustable carburetors, opening the idle needle valve a bit would sometimes let the obstruction pass (think kidney stone-ouch!) and then could be readjusted back to proper setting. These days, most carbs are completely metered and you'd have to pull the carb, pull the welch plug and blow the passage out with compressed air then install a new welch plug.
Sometimes and ultra sonic cleaning will take care of it.

What does the ethanol have to do with it? Well it does tend to cause degradation of rubber components and shedding of fuel lining. You might be lucky and only have some small bits in the bowl of the carb, so I'd clean that first and blow air where I could and hope for the best. But if that crap got into the idle fuel passage, it can be a bugger to get it out.

Honestly, depending on cost, sometimes just replacing the carb is cheaper in terms of time spent than doing all that other as described above.

 

Have 4 at work
all experienced fuel trouble and acted funny b4 finally quitting
bought new carbs off e-bay from china real cheap...... they run great first pull idle great

here's a link to carb ↓

https://www.ebay.com/itm/Carburetor-...72.m2749.l2649

 

I wholly endorse buying chinese carbs. Dollar for dollar it is cheaper that screwing around trying to clean the uncleanable.
I've installed dozens. Especially on snowblowers that sat too long between uses.