Diesel tractor over revving, why?

[Perry Holbrook]

I've got a 23 HP diesel Kioti tractor, 3 years old. As I was operating the backhoe at about 1/2 throttle, the engine suddenly over revved, smoked for less than 10 seconds and then died. I checked all fluids, temps, etc looked over the engine for any obvious problem and all was fine. To my surprise, it started right up and ran fine for the rest of the job.
The next time I used it, it happened again, this time when I was trying to make it happen by operating the throttle from idle to fast and back a few times in rapid movements.

The only thing that was a little different is I had filled the fuel tank that was near empty with fuel that had been in the fuel can over the winter.

Can anybody tell we what could be happening and what my next step should be?

Thanks.

[Tom M King]

I know nothing of that tractor but if it has not a tremendous amount of hours on it and a mechanical fuel pump, I would change the fuel pump. After checking the air intake to see if it's contaminated, I would change the mechanical fuel pump. It sounds like it's getting too much fuel for some reason. Might have been flooding out when it smoked and died.

[Bill Dufour]

First easy step, did any water come out of the filter drain. Drain the fuel tank and let any water settle out before pouring it back in.
Bill D

[Tom M King]

I’m interested to hear about the water. None of my tractors will let any water get past the filter. Too much water and they won’t start or would quit running.

[Tom M King]

How many hours on it?

[Jim Koepke]

Are you sure there wasn't any fuel contamination of any kind?

jtk

[Michael Schuch]

Since the RPM of a Diesel engine is only controlled by how much fuel it gets if the Diesel engine is overrevving either the fuel injection pump is sending too much fuel OR the engine is burning something else as fuel... i.e. engine oil.

Water in the fuel could cause the engine to cut out but it shouldn't cause the engine to overrev.

The engine probably has some sort of governor that cuts the fuel when the engine overrevs causing it to die... so the engine doesn't run away uncontrolled. I would guess the base cause of the engine cutting out is the overrevving.

I would suggest trying a forum that has more expertise on Diesel tractor engines than a woodworking forum. https://www.tractorbynet.com/

[Perry Holbrook]

How many hours on it?

The tractor has 250 hours

[Perry Holbrook]

Are you sure there wasn't any fuel contamination of any kind?

jtk

I'm guessing it is somehow related to the fuel. Don't understand how water would made the engine rev up. I looked at a diesel fuel conditioner at the auto parts store yesterday but thought it might be better to drain tank. But before doing that, I wanted to ask those smarter than me if I was on the right track. As far as going to another forum, I have great respect for members on this forum and know that someone will have the answer to most of lifes problems.

[Tom M King]

That’s still a new one. I’ve put over 3,000 hours on my utility tractor myself. The hour meter was broken when I bought it when it was 12 years old 33 years ago.

No question it’s a fuel issue.

[Ronald Blue]

I do believe it's a fuel issue. Not exclusively water though but with it happening right after adding fuel it most likely is. Does it have a fuel/water separator? If there is a drain where you can access and drain some fuel off, if there is water in the fuel it will come out first. So only drain a couple gallon if it's a valve you can close in to a clean container. The water will be easy to see if it's there. Get a new fuel filter as well. Whether you choose to drain all the fuel will be up to you but unless it's a large tank I probably would. You can still use it to start brush piles on fire etc. But it doesn't take much water to create issues. The surging and smoking are definitely a contaminated fuel symptom.

[Tom M King]

I've never seen a tractor fuel tank that didn't have a draincock at the bottom of the tank. You have to get under it, but even on the old ones it's pretty easy to operate. You can drain some out in a glass jar, and it's easy to see water in it. I've never seen a diesel that didn't have good enough filters on it to keep all the water out of the injectors though. At 250 hours, the fuel filter should not be a problem. I don't see any way this is a water issue, but don't claim to never be wrong.

I would check for oil in the intake before I would worry about it being a water issue.

Does it have both a lift pump and an injector pump? The "lift" pump is usually a mechanical pump. That's what I would put the priority on checking after a quick look over the linkage system to the injector pump.

[Maurice Mcmurry]

My little diesel Ford has a hand throttle and a foot throttle. Several times I have run over a stick or sapling that got stuck in the foot throttle linkage which has caused an unexpected rev. It does not smoke or die. It is alarming. I did a google search "2021 23 HP diesel Kioti tractor over rev smoking dying" The majority of the results are about bad fuel.

[Jim Becker]

When that's happened with my Kubota BX22 over the years (same HP engine) it's generally been in the fuel system...debris or bad fuel. Clean/change the filters and you may need to deal with debris in the tank at the outlet which can be a super pain in many tractors.

[Jim Becker]

I've never seen a tractor fuel tank that didn't have a draincock at the bottom of the tank.
Alas, that's not a thing with many subcompacts that utilize blow molded tanks that are complexly shaped and generally live under the seat, draping over the drivetrain.

[Tom M King]

Shame on them for not providing a tank drain. I’ve never had any dealings with that category of tractors though. My smallest utility tractor is a 70 ho category 2. I have been looking at them for getting a smaller one for pulling a topdresser with. This gives me one more thing to look at on them.

[Tom M King]

With no tank drain I would keep the tank full as much as possible. Some water does condense in them.

[Bill George]

It should have a glass bowl filter with a petcock in the bottom. Aside from a linkage sticking IF the diesel engine gets a shot of oil from a engine leak or bypass open it will happily burn it as fuel and it can not be shut off. I do not see how water in diesel could cause the over revving?

[Jack Frederick]

When I had my Kubotas I hung out at tractorbynet. No aspersions on the good suggestions here, but they do have a Kioti specific forum. Good luck with it.

[Maurice Mcmurry]

Several of the videos I watched talk about diesel bug and biofilm as well as water. Water puts the fire out. Diesel bug and biofilm cause the fuel delivery system to malfunction.

[Edward Weber]

Don't neglect to look at the air intake filter and associated items in conjunction with the fuel issue.

[Jim Becker]

It should have a glass bowl filter with a petcock in the bottom. Aside from a linkage sticking IF the diesel engine gets a shot of oil from a engine leak or bypass open it will happily burn it as fuel and it can not be shut off. I do not see how water in diesel could cause the over revving?
These are small tractors and that kind of feature isn't really a thing, unfortunately. Some folks will relocate the fuel filter and sometimes use a different type, but many of the subcompacts have simple in-line filters. Any draining is done by unclipping the hose from the tank side of the filter.

[Ronald Blue]

There won't be a glass bowl. They don't put those on bigger equipment anymore either. Many fuel tanks are mounted low these days. Under steps, the cab, or wherever with being able to mold any shape they want it fits in. So they use lift pumps to get the fuel to the injection pump. The beauty of these is no hand priming is required when filters are changed. Just cycle the key a couple times and they are bled. As Jim said it will be a molded tank. I have never looked for a drain on my Cub Cadet/Yanmar. With it happening right after adding fuel I'm confident it is fuel related. I saw this more times then I care to remember. There won't be a lift pump because the tank will gravity feed to the injection pump. You may have to pull a line to drain fuel off. I absolutely would put a new filter on as well. If contamination has already impacted engine performance it needs changed. The filter is all that protects the injection pump and you don't want to damage it.

[Bill Dufour]

Be glad this was not a giant engine in a container ship trying to thread the passage under the bridge as the engine failed. I agree with everyone else it is the new fuel. Either the fuel is bad or it pushed/dissolved old bad stuff into the pump.
It is much easier to drain and check the fuel then try to adjust any pump or linkages. Also easy enough to see the problem if it is bad fuel. That is way I recommended check filters first. Not because it is too likely but it should be done any time the pump is worked on, just in case.
Bill D

[Perry Holbrook]

An update. I remembered I had a filter kit that I bought with the tractor. The fuel filter had a drain but that produced about 1/4 teaspoon of water with the clear looking fuel. I replaced the fuel filter. Replaced the air filter. Fuel tank has no drain, so I pumped out as much as I could and put in 5 fresh gallons. We'll see if it happens again. BUT, I did remember something else. The manual, both hardcopy and online, says the engine holds 6 qts of oil. When I changed the oil at the first 100 hours, after adding the 6 qts the drip stick showed the level well above full. I just assumed the dip stick must the wrong and made a mental note to remember that when routinely checking oil levels. So today I changed the oil and filter and added just 5 qts and the dip stick still showed slightly over filled.
I don't see how all the manuals could be wrong and the dip stick right, but if that is true, the engine had at least 1 qt too much oil, which could have possibly found its way to the combustion chamber. Probably just overthinking.

It's probably just the fuel in the can went bad over the winter.

Thanks for the comments.

[Tom M King]

Diesel fuel sitting over a Winter shouldn’t be much of an issue. My 100 gallon tank has sat over Winters for 30 years with some in it. I do use some in Winters, but nothing like in grass growing season. I don’t burn a hundred gallons a year, so some of it is always over a year old.

The oil sounds suspect to me. I would want to know exactly how much is supposed to be in it.

[Perry Holbrook]

I want to apologize to everyone for wasting their time!

You know those large containers of motor oil at the auto parts store? Did you know they are 5 qts not 1 gallon? I didn't until now. How stupid can 1 old man be!

So, I had been running the tractor with an extra qt of oil and it finally said "I don't like this". Problem solved, just hope it didn't do any damage.

Good night.

[Tom M King]

No apologies needed. It's always an interesting problem to solve and not as much work when it belongs to someone else. I'd still like to know how the oil got in the combustion chambers.

[Bill George]

I want to apologize to everyone for wasting their time!

You know those large containers of motor oil at the auto parts store? Did you know they are 5 qts not 1 gallon? I didn't until now. How stupid can 1 old man be!

So, I had been running the tractor with an extra qt of oil and it finally said "I don't like this". Problem solved, just hope it didn't do any damage.

Good night.

Thats what I said, burning oil is just like diesel only no metering. I would Never adjust anything for a one time deal, I would check for binding and the oil burning thing. I have owned two diesels one a JD 650 a compact tractor and yes it did have the glass bowl with a drain, the other was a VW diesel which had a "special" filter to take out the water.

[Ronald Blue]

I want to apologize to everyone for wasting their time!

You know those large containers of motor oil at the auto parts store? Did you know they are 5 qts not 1 gallon? I didn't until now. How stupid can 1 old man be!

So, I had been running the tractor with an extra qt of oil and it finally said "I don't like this". Problem solved, just hope it didn't do any damage.

Good night.

Well now that we know you are human like the rest of us.... I don't think I've had one of those moments yet today but the day isn't over and I might have forgotten. These moments keep us humble.

[Bill George]

Interesting to note that he used a replacement filter that did have a drain. That should be a routine thing with a diesel which regardless of the size seem to get water in the fuel. As a farm kid I grew up around real tractors.

[Patrick McCarthy]

Perry, no apology needed. I always find these discussions interesting. Echoing one of your earlier comments, the breadth of knowledge and life experience people here are willing to share is impressive.

[Ed Aumiller]

Have an older Ford 3cylinder 4500 diesel backhoe... when is gets a fuel problem (lack of fuel) it will always rev up for a few seconds before it dies.... then will start and run normally... always a fuel problem....