L3901 Bogging Down Under Heavy Load

[mkreul]

My Kubota L3901hst has been giving me trouble for a few months. It runs fine when just driving around or under light loads. When under heavy loads it bogs down and eventually dies. I finally took it to a local Kubota dealer who is telling me that there is gas mixed with diesel in the tank. They said they ran it on the dyno and everything looked good, but when they dipped a rag into the fuel, it smelled like gasoline, so they lit it on fire and it "burned like gas would". I am the only person that has ever put fuel in it, I can say for certain no gas has mistakenly been used. Now they want $10,000 to replace the entire fuel system and of course KTAC insurance doesn't cover fuel contamination. This does not make sense to me, especially since this problem has persisted for several months. Any help on this would be appreciated.

 

[Jim L.]

I wasn't aware that the Society of Automotive Engineers had a "set it on fire" test. I would get a second opinion.

 

[85Hokie]

My Kubota L3901hst has been giving me trouble for a few months. It runs fine when just driving around or under light loads. When under heavy loads it bogs down and eventually dies. I finally took it to a local Kubota dealer who is telling me that there is gas mixed with diesel in the tank. They said they ran it on the dyno and everything looked good, but when they dipped a rag into the fuel, it smelled like gasoline, so they lit it on fire and it "burned like gas would". I am the only person that has ever put fuel in it, I can say for certain no gas has mistakenly been used. Now they want $10,000 to replace the entire fuel system and of course KTAC insurance doesn't cover fuel contamination. This does not make sense to me, especially since this problem has persisted for several months. Any help on this would be appreciated.

I would syphon the hell out of the old tank either with mechanical pump or allow it to spill from nearest hose connection.

Then I would add 100% clean fuel from another container from a diesel supply known to be "good" - run it for a bit - after 10-15 minutes the contaminated fuel will have run its course through the system - even if it pumps back a bit to the bypass, the dilution would be very effective.

And then test it under load - despite being the only user - is it possible that someone "did a good deed" filling up your diesel fill tanks?

 

[6869704x4]

Notice any smoke while it's bogging down?
How many Kubota dealers have dynos?

 

[GrizBota]

They told you $10k with a straight face? Wow, zero conscious. The negative karma points will kick thbutt hard someday.

Have you replaced the fuel filter?

Odd that an actual dyno couldn’t tell them what your butt dyno can. And the dyno says all is good, but the “burning rag” test can substantiate a $10k repair the dyno can’t sense. I’m always a bit pessimistic, but I smell a rat.

 

[whitetiger]

Notice any smoke while it's bogging down?
How many Kubota dealers have dynos?

Quite a few...

 

[NCL4701]

If contamination of fuel or any other fluid is suspected but not severe enough or of a type to be definitively determined, or is questionable for any reason, sending a sample to a lab for testing is the appropriate way to verify what the fluid actually contains. For a $10K repair, a lab test is reasonable. If you drain the fuel currently in it, drain it into a clean container and save at least a quart of it in case you need it later for testing.

Also, you said the only symptom is bogging under load; otherwise runs fine. If it “everything looked good on the dyno” that means it was NOT bogging under load for the dealer. So they essentially told you they were unable to get it to repeat the reported problem, then came up with a totally different problem. They haven’t even said exactly WHAT is damaged in the fuel system, just “gas in diesel based on non-standard test; hand me $10,000”.

I would definitely get a second opinion. Chances I would let that dealer work on my equipment or even so much as buy a hat from them going forward would be near zero.

Also, if you have insurance on it, check with them to see if fuel contamination is covered. Some does cover accidental fuel contamination, some doesn’t. On a $10,000 repair (if that’s really what it needs) it’s worth a phone call to find out.

I have been personally involved in a handful of cases (like maybe 15 cases involving a total of around 500 vehicles over the past 33 years) of gas being introduced into diesel tanks at fuel stations by error of the delivery person, resulting in gas being mixed in with diesel in the diesel tank at the fuel station. Vehicle drivers then fill up with diesel and contaminate their fuel system with gas through no fault of their own. Sometimes that causes various severe damage such as bent rods from severe pre-ignition, damage to fuel pump(s) from lack of lubrication, etc..; but more typically it just takes out the injectors, even on the “new” high pressure systems.

The dealer may be 100% correct, and completely above board with everything they’re saying and doing. Based on your description of what has transpired it appears much more likely they didn’t even have the courtesy to buy you dinner before asking you to bend over for a brief drive.

 

[mikester]

Go to a new dealer.

If these guys claim to have a dyno to test your machine but use a rag smell and burn test to inspect fuel quality they are FOS.

Get a sample of your fuel tested and go after warranty if it's in spec.

 

[mkreul]

I have not noticed any smoke from the tractor.
I do have KTAC insurance, but apparently they do not cover fuel contamination even if I claim vandalism. I talked to my insurance agent that holds my homeowners policy and he said they might cover it, but we would have to prove vandalism.
Fuel filter was replaced just a few weeks ago and the problem continues to persist.

 

[SDT]

My Kubota L3901hst has been giving me trouble for a few months. It runs fine when just driving around or under light loads. When under heavy loads it bogs down and eventually dies. I finally took it to a local Kubota dealer who is telling me that there is gas mixed with diesel in the tank. They said they ran it on the dyno and everything looked good, but when they dipped a rag into the fuel, it smelled like gasoline, so they lit it on fire and it "burned like gas would". I am the only person that has ever put fuel in it, I can say for certain no gas has mistakenly been used. Now they want $10,000 to replace the entire fuel system and of course KTAC insurance doesn't cover fuel contamination. This does not make sense to me, especially since this problem has persisted for several months. Any help on this would be appreciated.

Like ohters have recommended, thoroughly flush the fuel system and fill with new fuel. Operate for several minutes and have another go under under load. If still unsitisfied, take it to a different dealer.

Dealers are in business to make money for the owners and some (many/most) will do whatever it takes to do so.

 

[mdhughes]

I would hope that the dealer would have check this, but I would pull the fuel line going to the water seperator and see what kind of flow you get from the tank. Use some kind of clamp to clamp off the hose before taking it off. Get a container and release the clamp. If the fuel doesn't flow out at a good rate, I would say that is your problem. They have been several people on the forum that had an issue and there was something clogging the outlet of the fuel tank.

 

[GrizBota]

The only “evidence” of fuel contamination is the “rag burn” test the dealer claimed to have conducted right before they said they could fix it for $10k. I don’t know for sure, but I suspect there’s a 90% chance what you’ve been told is 100% hogwash.

Here’s a test you can perform yourself. Obviously you need to be safe. The YouTuber didn’t even have a fire extinguisher in the frame. And I’m not sure he understood the proper usage of a first aid kit. But for what it’s worth (and I’m thinking it’s a grade or two above the rag burn test):

YouTube Gas/Diesel Flame Point

 

[jimh406]

I'd also suggest doing the easy things first. That is, drain the fuel, and change the fuel filter.

Fwiw, bogging down under load is also what happens when a DPF is clogged. How often does it Regen and do you remember the last time? How long ago was that?

When you add the fuel, I'd overdose it on fuel additive. I'd add a bottle. I prefer Diesel Kleen that has Cetane booster. It makes the fuel burn hotter which can help clear the DPF/clean it. It will need to run a while at higher RPM to clear the DPF.

Depending on where you buy your fuel and how they filled their tanks, it may or may not have been contaminated. Note: the fuel location could have put some amount of gasoline in their fuel. Frankly, I think you would have noticed a significant amount of gasoline in your diesel.

 

[Runs With Scissors]

I'd also suggest doing the easy things first. That is, drain the fuel, and change the fuel filter.

Fwiw, bogging down under load is also what happens when a DPF is clogged. How often does it Regen and do you remember the last time? How long ago was that?

I was thinking the exact same thing, but I don't know anything about the exhaust systems on tractors and this whole DPF thing.

I know that a car that has a plugged exhaust/cat will exhibit similar symptoms.

They will purr like a kitten at idle and mild load, but fall on their face at high load.

Worth considering I guess.

 

[NCL4701]

A plugged air filter will exhibit same symptoms as a plugged exhaust.

At a very basic level, it sounds like it’s getting enough air and fuel in the right quantities when there’s low demand for both. When there’s high demand for both, it isn’t getting enough of one or the other (or both but more likely just a problem with one or the other).

Air restriction: could be on exhaust side (banana in tailpipe/plugged DPF, etc.) or on intake side (filthy air filter/mouse nest in intake, etc.).

Fuel restriction: start at tank and work toward injectors. Debris/restriction in tank, water separator, fuel filter, etc. Others have given some good practical advice on checking the fuel system side of it.

Past that, the WSM should provide guidance on fuel system testing. Even if you can’t do that yourself for whatever reason, I would suggest educating yourself to the degree practical on what the WSM has to say about testing and repairing the fuel system. That gives you the ability to intelligently discuss the issue with the repairer, reducing the chance of a repeat of the burning rag incident.

 

[GreensvilleJay]

wow, just when you think you've heard it all.... a tractor dyno AND a flaming rag test...sigh.

curious. How many tanks of diesel have you gone through in the MONTHS since the bogging down appeared ?1 or 5 or 25 ?

As others have said...replace ALL the filters(fuel and air), purge the tank and lines, add fresh fuel,prime and run the tractor,at times hard. It sounds like a DPF problem.

Consensus here says to throttle up an diesel with DPF to keep it from clogging.
Next time you're at the dealer,please take a picture of the 'tractor dyno' ,I'm sure everyone here would like to see it !!!

 

[rc51stierhoff]

My Kubota L3901hst has been giving me trouble for a few months. It runs fine when just driving around or under light loads. When under heavy loads it bogs down and eventually dies. I finally took it to a local Kubota dealer who is telling me that there is gas mixed with diesel in the tank. They said they ran it on the dyno and everything looked good, but when they dipped a rag into the fuel, it smelled like gasoline, so they lit it on fire and it "burned like gas would". I am the only person that has ever put fuel in it, I can say for certain no gas has mistakenly been used. Now they want $10,000 to replace the entire fuel system and of course KTAC insurance doesn't cover fuel contamination. This does not make sense to me, especially since this problem has persisted for several months. Any help on this would be appreciated.

If there was an emoji for WTFO, I would have used that. It be hard for me to believe that diagnosis / test method. Maybe they are correct, but I don’t really know myself…I know what would have a hard time trusting that. I think I’d deeply consider some of suggestions others have shared from self check items (if those were not done already) and easy things first as jimh406 and others said, second opinions, and the script from 85Hokie, NCL4701 and others…some great suggestions above to follow up on before handing them over 10k IMO based on a burn test. Good luck. I hope it is something simple. Keep us posted.

 

[skeets]

One more thing, if I may. Where do you get your fuel, I have seen some places where the truck used for diesel is also used for gas maybe a little bit but not much mixed together, OR someone messed up and pumped gas into the diesel tank, it happens. Maybe get your fuel from a different source.

 

[mkreul]

Just to keep everyone updated. I told the dealer I was going to take the tractor back home and try some other fixes before I shelled out 10k for them to fix it. They got really defensive and didn't want to give me the paperwork on what they had performed so far. So another major red flag. Also, I asked them if they would perform a diesel contamination test and they said no.
To answer some of the other questions that have been asked: I have probably gone through at least 10 tanks of fuel since this issue started, that's why I thought the "gas in the tank" diagnosis was fishy. I recently changed the fuel filter and air filter. I believe the last DPF regen was a month or so ago. It seems to regen 2-3 times per year. I usually run it at high rpms to keep the DPF clean.

 

[Yooper]

They don’t want to give you the paperwork? !