Engine lost power RPM

[Jeff Enders 3]

One of my 312-8 garden tractors suddenly lost power. I could hardly get it in the barn. The RPM's just dropped right off. I've checked everything I know how to check, which isn't alot, Ha Ha.  But what would make the engine drop right down to below idle? Any suggestion?

[Ed Kennell 35,963]

Lack of fuel.      Fuel tank vent clogged?

[lynnmor 6,834]

Throttle cable broke or came loose?

[gwest_ca-(File Mod) 10,531]

 

If you have an original muffler as was on my 1990 model 312-8

A baffle in the muffler can burn off and plug the 2nd baffle. The engine will run smooth but not rev up.

When it happened to me the baffle fell off it's location when the engine is shut off. Restart and run OK until the floating plug works it's way to the hole in the second baffle again.

If you bang the muffler you may hear the floating plug rattle.

The inlet tube of the muffler goes through to the far side of the can. The tube is drilled full of small holes for the exhaust to exit and there is a cap on the end of the tube. The tube burns off at the holes leaving the cap and a bit of the tube to float around.

[Jeff Enders 3]

Thank you for the thoughts, I'm on it. 

[ranger 1,657]

I had the same thing with a big diesel engine. It would start and run at idle all day long, but cut out if revs increased? It had been diagnosed with all manner of reasons why, but then we noticed that the exhaust was very quiet? There was virtually nothing coming out from the tailpipe! The D.P.F had broken up internally, causing a huge restriction. Removing the engine side differential pressure sensor allowed enough gasses to escape and the engine would then rev up. Try putting your hand close to the silencer outlet to see if it feels restricted. If it’s not the exhaust that’s the issue, then as others have said it’s probably a fuel supply problem?

[tunahead72 2,346]

A massive buildup of carbon in the combustion chamber MIGHT cause the symptoms you're seeing.  Have you ever pulled the head to see what it looks like in there?  You could start by removing the spark plug and shining a flashlight in the opening to get a clue, maybe clean the plug with a wire brush and set the gap while you're at it.

 

[Jeff Enders 3]

I appreciate all the advice. I'm knew to this so am still learning the ins and outs of the forums. I checked all the areas that the members advised to. Everything looked good, except fuel flow. 

I am going with a new fuel pump on this issue of losing RPM' have after market pump. Looking for OEM. Will add new fuel filter and shut off valve at same time. 

My Son and 2 Grandson's and I are interested in going an event, just deciding on what one. Oldest Grandson (12) is looking for his 1st WH, so I'm checking out the classifieds. 

[Fordiesel69 226]

Jeff,

 

I was unable to read all the suggestions but because you have a kohler 12HP the diagnostics are easy.

 

Do you have a k series (with a round coil, condensor, and points) or do you have the newer Magnum M12 where the sparkplug wire comes out of the flywheel blower housing?

 

Either way, remove air filter, get engine running, and make sure the choke flap is open, then grab a hold of the governor link on the carburetor (throttle shaft) and see if you can speed the engine up and down that way.  Report back how its acting.  If it was fuel flow, I would assume the engine would have died several times, and I would assume you would have had to use full or partial choke.   I have indeed had throttle linkages pop off many different engines and cuase it to just remain at low / idle the throttle.