Kubota rough running and smoking

[bandit67]

It's not simply the altitude and a case that you have to live with it. I run my machine at 8500', and the only time it runs like yours does is at initial startup when the engine is very cold. My 7.3L diesel runs the same way at initial very cold startup, for longer and with more diesel odor than the little Kubota engine. But both engines clear up rather quickly, and do not do that at all once warm, especially at higher rpms.

Does it do this year round? The newer ULSD fuel doesn't burn as well as the LSD did, and in the cold weather, I've found that initial startups are much worse now. It is possible that the fuel you are getting is very low quality, as I've heard of some really bad fuel in certain parts of the country. Before you take it in to the dealer, you may want to try draining the off-road fuel and run a gallon or two of regular #1&2 winter blend ULSD on-road diesel and see if there's any change.

If not, take it in and have the mechanics run all the tests on the injection system, check cylinder pressure, etc.

 

[Jon-ecm]

My guess is that it's your injectors; Take your injectors to a shop and get them to test their blow off pressure...and spraying characteristics if they are starting to let fuel out at too low of a pressure they will make the engine run rough and they will not mist the fuel so it will have incomplete combustion
If that is the case usually replacing the springs will fix that...Another thing that happens is sometimes they spray in a jet pattern vs a mist...that can also cause incomplete combustion and a rough running engine.


Jon

 

[BIGSKYSNOWBLOWER]

Did you by any chance accidentally mix some gasoline in with your diesel? I have seen this happen several times, to check ,smell in your fuel tank. Also have you used starting fluid on some cold day? If you use to much it can blow the top of the pistons off. Good luck.

I am pretty sure gasoline has not gotten into the tractor. It would have had to come from the diesel pump where I buy the diesel, and I have never used starting fluid. I keep the freeze plug heater plugged in all the time and never have any issues getting it started.

 

[john_bud]

Could be some water in the fuel. Or a stuck injector.
jb

 

[RickB]

I am pretty sure gasoline has not gotten into the tractor. It would have had to come from the diesel pump where I buy the diesel, and I have never used starting fluid. I keep the freeze plug heater plugged in all the time and never have any issues getting it started.

Last month, one of my more knowlegeable customers walked right past the diesel pump he usually buys from and filled his yellow jug with gasoline. He proceeded to dump it into his NH TZ24D. Needless to say, it ran like crap, and he didn't know why. I think I'd drain your tractor's tank and start fresh before I did anything else.