Kubota L3400. I changed oil, oil filter, all air filters, and fuel filter less than 20 hours ago. All OEM parts for my specific model. Recently very hot in Indiana 90+ degrees days. Tractor runs great for 15- 20 minutes and then acts like it is starving for fuel with sluggish to no response on the gas pedal. If Inlet it sit for a few hours, it is fine for 15-20 minutes , and then same thing. I think I have a vapor lock with fuel getting too hot somewhere causing the issue. I have tried taking off the fuel cap to see if it would release pressure. Did not work. Looking online having trouble finding maybe if there is a clogged fuel vent ? Also engine temp is running normal and not overheating. Air filters very clean. I have a attached a fuel system diagram online I found. I am going to try and find the vent pipe on there today. Any help or advice appreciated
Kubota L3400 Vapor Lock???
- Thread starter Dj654
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So welcome to the forum... normally, these threads turn out to be junk in the fuel tank or algae in the tank. Something floats around the tank until it get sucked into the outlet pipe. You can check a couple other things, like crack the fuel cap to make sure the vent is not plugged up (has happened, cause a vapor lock of sorts).
You can add a Biocide https://powerservice.com/psp_product/bio-kleen-diesel-fuel-biocide/
how fresh is the fuel??
You can try draining the tank by removing the line going to the fuel filter to check if the flow stops.... then you know something is in the tank.
PS. Many years on a couple forums - never a vapor lock incident!
Edit: How hot is your temperature gauge reading??? If you are the first one to vapor lock, you would have to have high temps on the gauge, which means you need to clean out the radiator fins (they might be clogged with chaff). Although, I over heated and a few others have over heated and fuel was NOT an issue.
how fresh is the fuel??
You can try draining the tank by removing the line going to the fuel filter to check if the flow stops.... then you know something is in the tank.
PS. Many years on a couple forums - never a vapor lock incident!
Edit: How hot is your temperature gauge reading??? If you are the first one to vapor lock, you would have to have high temps on the gauge, which means you need to clean out the radiator fins (they might be clogged with chaff). Although, I over heated and a few others have over heated and fuel was NOT an issue.
North Idaho Wolfman
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Temp is running normal at all times. No overheating. Fuel is fresh. We use the tractor daily. I add seafoam or injector cleaner every 5 tanks or so. I was hoping not to pull lines and get sir in the lines.
North Idaho Wolfman
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A very long shot, make a small wire screen (like a tiny fish net) and see if you can screen out what's floating in the tank. If it works, you'll be the first one to do it. Removing the tank is a pretty big job...
One guy drained his tank and was going to try and shop-vac out the crud. We never did hear back if he was successful or if he blew himself up...
One guy drained his tank and was going to try and shop-vac out the crud. We never did hear back if he was successful or if he blew himself up...
Russell King
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Does a biocide break down the slime (clean out a plugged line)? Or does it just kill and stop further growth?
Does he need to clean and the use biocide is another way to ask?
If you trust AI... this is what google said... "Biocides kill the microbes but do not remove the resulting sludge (dead organic matter). This sludge can still clog fuel filters." But doesn't say that it would block the outlet, just clog the filter so MAYBE it might work. I can't see it hurting to try...
North Idaho Wolfman
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Depends on the amount of algae / bacterial growth and type of biocide you use.
The stuff I use eats it up and breaks it down so it get to the filter.
Is this a gear drive or hydrostat transmission? If hydrostat, put a PTO driven implement on it and see if it is the engine having trouble producing power OR the transmission that is having problems with transferring power after 15-20 minutes.
Rodger
Rodger
I had a similar issue this is going to sound a little bizarre but the next time you feel like the tractor is vapor locking loosen the fuel cap if the engine starts to run normally again the vent in the cap may be blocked that was the issue I experienced good luck
North Idaho Wolfman
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L3450DT-GST, Woods FEL, B7100 HSD, FEL, 60" SB, 743 Bobcat with V2203, and more
North Idaho Wolfman
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Lifetime Member
Equipment
L3450DT-GST, Woods FEL, B7100 HSD, FEL, 60" SB, 743 Bobcat with V2203, and more
I tried that earlier and it didn’t work. I also cleaned out the fuel return line, and that didn’t work as well.
RCW
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Before I played with any additives, etc. - - this is what I would look for:
Does an L3400 have a clear bowl for the fuel filter/water separator?
If so, when the tractor is starving for fuel, is the filter bowl full of fuel, or is it partially empty?
If partially filled, means could be a restriction to the filter.
In some Kubota models, the inlet fitting to the filter housing is notorious for getting some trash in it. Quite of few folks have had a similar problem.
Don't know if an L3400 is one of them but certainly has some of the characteristics.
No experience myself, but I would take the fuel line from the tank off of the filter housing inlet. Drop the fuel line from the tank into a bucket. Does it run freely with good volume? Tank is above the fuel filter, so it should run pretty good if the tank is apparently okay.
Probably will need to pinch off the line gently with a pair of locking pliers if there's no shut-off.
Then take the filter back out.
Run a small wire, etc. into the inlet fitting and see if it's fouled with some trash.
These will determine where the restriction (if there is one) might be.
Sometimes tank restrictions can be intermittent. Something floats around the tank until it gets drawn to the tank outlet......hard work and low-fuel conditions can exacerbate the problems.
Would need to go through whatever bleeding process is needed for your tractor after the exercise and stuff put back together.
PS - - below is what I started with, and re-thought the problem when I was typing. Still might have some value, so didn't just delete it.
Some guys have gotten temporary relief using a little air blowing through the fuel line before the filter(s) back into the tank. Don't want much pressure.
Some causes of interrupted/ fouled flow I recall on OTT have been biomass, bugs/grass/junk, etc., and corrosion of the fittings at the tank outlet.
Several years ago, quite a few folks had biomass problems. I got so I use a Biocide as a Preventive year 'round since.
I use Power Service Bio-Cleen. Don't know if good, but it's available locally.
Quite a few swear by Stanadyne and Soltron that @North Idaho Wolfman mentions.
Does an L3400 have a clear bowl for the fuel filter/water separator?
If so, when the tractor is starving for fuel, is the filter bowl full of fuel, or is it partially empty?
If partially filled, means could be a restriction to the filter.
In some Kubota models, the inlet fitting to the filter housing is notorious for getting some trash in it. Quite of few folks have had a similar problem.
Don't know if an L3400 is one of them but certainly has some of the characteristics.
No experience myself, but I would take the fuel line from the tank off of the filter housing inlet. Drop the fuel line from the tank into a bucket. Does it run freely with good volume? Tank is above the fuel filter, so it should run pretty good if the tank is apparently okay.
Probably will need to pinch off the line gently with a pair of locking pliers if there's no shut-off.
Then take the filter back out.
Run a small wire, etc. into the inlet fitting and see if it's fouled with some trash.
These will determine where the restriction (if there is one) might be.
Sometimes tank restrictions can be intermittent. Something floats around the tank until it gets drawn to the tank outlet......hard work and low-fuel conditions can exacerbate the problems.
Would need to go through whatever bleeding process is needed for your tractor after the exercise and stuff put back together.
PS - - below is what I started with, and re-thought the problem when I was typing. Still might have some value, so didn't just delete it.
Some guys have gotten temporary relief using a little air blowing through the fuel line before the filter(s) back into the tank. Don't want much pressure.
Some causes of interrupted/ fouled flow I recall on OTT have been biomass, bugs/grass/junk, etc., and corrosion of the fittings at the tank outlet.
Several years ago, quite a few folks had biomass problems. I got so I use a Biocide as a Preventive year 'round since.
I use Power Service Bio-Cleen. Don't know if good, but it's available locally.
Quite a few swear by Stanadyne and Soltron that @North Idaho Wolfman mentions.
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