# Kobota 3 Cylinder Diesel Random Power Loss and Stalling



## gw1500se (Dec 28, 2019)

I have a Kobota 3 cylinder diesel on a Grasshopper 721D mower. At random times (loaded or idling) it loses power then either recovers or stalls. It is very hard to start in that it sputters or lags before finally coming up to speed. I had the injectors rebuilt and tested but that did not help. I added stiction eliminator to my oil change and that seemed to clear the problem up after a couple of tanks full of fuel. However, the problem has now returned and the stiction eliminator does not seem to help any more. I am guessing the problem is the injector pump but that is an expensive part with no assurance it really is. Can someone suggest other possibilities or how to go about diagnosing the problem? TIA.


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## thepumpguysc (Jan 25, 2015)

It sounds as if theres a fuel SUPPLY problem.. either coming from the fuel tank, a clogged fuel filter or a faulty supply pump..


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## tractorfacts (Dec 7, 2019)

thepumpguysc is right on track. With the problem coming and going it is not likely to be the injection pump. Clean your entire fuel system up to the injection pump. Also it would not be a bad idea to check your air breather, if it has a rubber hose running from the breather to the intake make sure that it is not collapsing the hose and starving the engine. It does sound more like a clogged fuel system or a weak supply pump.


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## thepumpguysc (Jan 25, 2015)

I like to take the rubber hose off from the tank to the fuel filter or right off AT the tank & drain it into a 5 gal. bucket & WATCH the flow for a few gallons..
Ur watching for any slow down.. like some "floaters" inside the tank blocking the outlet.
U might be able to google a break down of the fuel tank to find out if it has a screen on the outlet pipe. 
The elbows on the fuel filter are KNOWN to collect garbage.. pull the hoses off & have a look..


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## gw1500se (Dec 28, 2019)

Thanks for the replies. I'm sure it is not the filters because replacing them did nothing. I will pull the hoses and clean them along with checking the outlet from the tank. I found there is a type of algae that grows in diesel fuel so that may be the problem as well.


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## Bob Driver (Nov 1, 2017)

I have a customer (actually the mailman) that has a 721D. His has a horizontal shaft CH25, not the diesel, but that thing is a *BEAST* of a mower. 72" deck and an awesome ground speed. That thing will cut some grass....


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## gw1500se (Dec 28, 2019)

It does a hell of a job, when it works.


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## Bob Driver (Nov 1, 2017)

I lean toward agreeing with a fuel problem. Diesels are much more sensitive to fuel/water contamination than gasoline engines. Drop a sample of fuel in a clear glass jar and let it sit overnight. If you've got water, or algae, you'll see it. 

Do you run "dyed fuel", or regular pump USLD? Dyed fuel is like running 98 octane gas. The fuel sits in storage tanks a lot longer, because of demand, and there is more chance of contamination.


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## lewis cassill (Jan 12, 2018)

thepumpguysc said:


> It sounds as if theres a fuel SUPPLY problem.. either coming from the fuel tank, a clogged fuel filter or a faulty supply pump..


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## lewis cassill (Jan 12, 2018)

Possibly the fuel solenoid. I bought a new LS with a mitsubishi engine. I had a multitude of problems from day one. I sent it back to the dealer for warranty service. Called to see if my tractor was repaired. The guy said he had no record of me being a customer of his. Never seen my tractor again. I have also been told by farmers that a thousand hours is the lifetime of all asian tractors. This must be the case as i bought a new Branson and it has issues.


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## Hoodoo Valley (Nov 14, 2006)

Were you making financed payments on the LS?


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## lewis cassill (Jan 12, 2018)

Hoodoo Valley said:


> Were you making financed payments on the LS?


 I paid cash. Im not the only one to have had this problem.


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## Hoodoo Valley (Nov 14, 2006)

Ouch. I've never heard of such a move. That's crazy.


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## Raymond Henrie (Sep 18, 2019)

gw1500se said:


> I have a Kobota 3 cylinder diesel on a Grasshopper 721D mower. At random times (loaded or idling) it loses power then either recovers or stalls. It is very hard to start in that it sputters or lags before finally coming up to speed. I had the injectors rebuilt and tested but that did not help. I added stiction eliminator to my oil change and that seemed to clear the problem up after a couple of tanks full of fuel. However, the problem has now returned and the stiction eliminator does not seem to help any more. I am guessing the problem is the injector pump but that is an expensive part with no assurance it really is. Can someone suggest other possibilities or how to go about diagnosing the problem? TIA.


I have a Yanmar that once did something similar and I discovered the fuel intake line had a small crack that allowed air to be sucked in by the injector pump. Look for a small fuel leak along the intake line as an indicator. It may be just a damp spot and not a drip.


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## gw1500se (Dec 28, 2019)

Thanks for all the replies. I will be working on it this weekend.


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## DK35vince (Jan 22, 2006)

lewis cassill said:


> I have also been told by farmers that a thousand hours is the lifetime of all asian tractors. This must be the case as i bought a new Branson and it has issues.


Wow, that's news to me.
I'm at 2238 hours on my Korean built compact tractor and its still working like new.
There are a ton of Kubota and other Asian tractors out the with many thousands of hours


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## Richard O. Braun (Apr 14, 2019)

gw1500se said:


> I have a Kobota 3 cylinder diesel on a Grasshopper 721D mower. At random times (loaded or idling) it loses power then either recovers or stalls. It is very hard to start in that it sputters or lags before finally coming up to speed. I had the injectors rebuilt and tested but that did not help. I added stiction eliminator to my oil change and that seemed to clear the problem up after a couple of tanks full of fuel. However, the problem has now returned and the stiction eliminator does not seem to help any more. I am guessing the problem is the injector pump but that is an expensive part with no assurance it really is. Can someone suggest other possibilities or how to go about diagnosing the problem? TIA.


I also have a Grasshopper 721D with over 1300 hrs. I've never had a problem with it not running right. From what little I know about diesel engines, It sounds like you may have air in the fuel system. It may pay to check all of your fuel connections and try bleeding the system. Also, I have always added an additive to my fuel that helps to remove any moisture.


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## bmaverick (Feb 20, 2014)

Raymond Henrie said:


> I have a Yanmar that once did something similar and I discovered the fuel intake line had a small crack that allowed air to be sucked in by the injector pump. Look for a small fuel leak along the intake line as an indicator. It may be just a damp spot and not a drip.


Exactly. My old John Deere 850 (Yanmar) had old fuel hoses and did just that too. Replaced the hoses and it did run again.


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## bmaverick (Feb 20, 2014)

lewis cassill said:


> Possibly the fuel solenoid. I bought a new LS with a mitsubishi engine. I had a multitude of problems from day one. I sent it back to the dealer for warranty service. Called to see if my tractor was repaired. The guy said he had no record of me being a customer of his. Never seen my tractor again. I have also been told by farmers that a thousand hours is the lifetime of all asian tractors. This must be the case as i bought a new Branson and it has issues.


Did you get a receipt the tractor work was being done or anything??? Time for the law to look into that!


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## lewis cassill (Jan 12, 2018)

The law is already involved. They figure i was sold a new tractor that was stolen from another dealers lot or it had been reported stolen for the insurance and then sold to me for cash. It was likely exported. I should have known something was fishy when i could never get the dealer to service it or replace defective parts.


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