runs rough after about an hour

SydKen · Apr 4, 2009

Hi Guys,
I got my YM3000 out for the first time this season today and after running for about an hour it began to run rough. I started noticing it and it slowly got worse. Came home this evening and it started right up and ran great but after about an hour it started doing it again.

Any ideas?

carpenter383 · Apr 4, 2009

This may not even be close, but make sure the feul cap is vented good. Other than that make sure it's not getting hot

LMTC · Apr 4, 2009

"About an hour". If it's closer to 20 minutes each time I would consider injector, then head. I've seen both (when damaged) create rough running when hot, but not cold. If it's a vent issue in the fuel tank, it should eventually just shut down until the tank is vented.

RickB · Apr 5, 2009

Change the fuel filter, and while the filter is off, check the fuel flow from the tank to the filter head. Save the gloom & doom catastrophic stuff until the simple and cheap has been eliminated from suspicion.

SydKen · Apr 5, 2009

I will pay close attention to the time today as I finish cutting the grass, but I'm pretty sure it was more like 45 minutes to an hour instead of 20 minutes. I just replaced my fuel filter at the end of last season so i don't think that's it. I am curious about the venting though. I assume that if it starts running rough and I loosen the cap on the fuel tank it will smooth out if it is a vent issue?

RickB · Apr 5, 2009

Could also be about a 75% mix of gasoline in the diesel fuel. They will run more or less OK until they get warm.

LMTC · Apr 5, 2009

RickB said:
Change the fuel filter, and while the filter is off, check the fuel flow from the tank to the filter head. Save the gloom & doom catastrophic stuff until the simple and cheap has been eliminated from suspicion.

The fuel filter was elminated when it ran for an hour, ran rough, then ran well when cooled down. I have never seen a fuel filter issue cause repeated rough running after an hour (or even 20 minutes) only to clear up when the engine cools down, and then reoccur when hot. It's just not an issue that fits those symptoms. The clearing up when cool is a major factor...it means the source of the problem is not consistent, i.e., it probably has to get hot to mal-perform.

RickB · Apr 5, 2009

Opinions differ. Cylinder head problems don't come and go, in my experience. A mostly plugged filter or restriction in the tank outlet are common, easily cured, and are very much within the list of possible causes. Prudent troubleshooting begins with the easy, cheap stuff. I can't tell you how many times I have heard " Don't bother to check the fuses, I did and they are all OK" only to find a blown fuse. Last year's fuel filter is still last year's fuel filter, and last time I checked, cheaper than a head gasket and easier to change.

kenmac · Apr 5, 2009

do you have a temp light / gauge ?? If light. check to be sure temp light/ sensor is working properly

LMTC · Apr 5, 2009

RickB said:
Opinions differ. Cylinder head problems don't come and go, in my experience. A mostly plugged filter or restriction in the tank outlet are common, easily cured, and are very much within the list of possible causes. Prudent troubleshooting begins with the easy, cheap stuff. I can't tell you how many times I have heard " Don't bother to check the fuses, I did and they are all OK" only to find a blown fuse. Last year's fuel filter is still last year's fuel filter, and last time I checked, cheaper than a head gasket and easier to change.

Opinions do differ.....I have on several occasions seen a tractor with a bad head run well for 20 minutes or so, then run badly. On cool down, same pattern. I wouldn't call that "come and go", I would call it a repetitive pattern. But then your experience may go well beyond mine with these tractors.