# Kubota fuel prob



## davang (Apr 7, 2010)

So my Kuboat L4400 with 200 hours chugs and dies intermittently under load. Checked fuel flow from tank all the way past the filter assembly. There is great gravity flow up to the fuel pump.

So I removed the fuel pump and when I pump it manually it makes a squawking sound which I assume it's pulling in air. I cover the inlet hole with my thumb and pump it a few times, it creates a suction and pops when i lift off my thumb. So I think it's okay too.

The next thing up the line is the injector pump. What should I try next?

Jeff


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## carcajou (Jan 28, 2011)

Plugged vent in the supply? Tried running it with the fuel cap loose?


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## Wethay (Jul 17, 2015)

Might be that the transfer pump outlet check valve is letting fuel flow back in. Does the transfer pump have a screen? If you have a electric fuel pump it maybe worth bypassing the fuel transfer pump temporarily. At 200 hours you shouldn't be having problems. Fuel quality may also be an issue. I'm interested in what you find.


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## JD3430 (Jan 1, 2012)

Check for critters in the tank, too.


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## luke strawwalker (Jul 31, 2014)

Yeah I've had dust and crud get into the tank (despite a good cap) and form "rat turds" on the bottom of the tank that can securely plug off the tank outlet valve opening. We replaced the outlet valve with one with a screen in it and that helped immensely, as well as draining the tank into buckets and then filtering the diesel back in through a screened funnel.

Course, screened outlets aren't the answer for everything. BIL's Case 2390 had algae in the tank and it would completely plug off the screened "sock" over the end of the siphon tube... tractor would go to no power and/or outright stall. Had to blow back through the line to bubble/blow crap off the screen so fuel could flow again. He finally pulled the screen off the end of the tube last winter, so now we just keep an eye on the sediment bowl and clean the screen in there periodically as needed. At least I'm not having to blow back through the line through a cupped hand like before...

Later! OL J R


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## Greasy30 (Mar 15, 2010)

Not sure what year your Bota is, but my 2015 did sorta the same thing and it was due to water in the fuel. Drained the tank and lines, put new fuel in and ran like a champ.

Asked the dealer about it and he said that was one of the down falls with the new Tier 4 engine a little bit of water could make the engine stop.


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## Tx Jim (Jun 30, 2014)

I once owned a Kubota M4900 that the engine would stop running. I found a small stopped up screen in the water seperater fuel control cut-off valve. Cleaned screen problem resolved.


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## JMT (Aug 10, 2013)

The fittings on/in the water separator on my M120 get plugged with bugs. I think it is spiders that nest in the end of the fuel nozzel on my bulk tank and the hose of my transfer tank. I always try to knock them out before filling tanks but it seems like some may be getting in the fuel. The m120s fuel/water separator needs blown/cleaned out about every 1500 hours it seems.


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## jeff outwest (Sep 13, 2009)

My neighbor bought a used 125X would do the same thing. Found that the lines from the fuel tank were reversed. Being the same size would be easy to get them on wrong. Changed that and bam, a new tractor.


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## hog987 (Apr 5, 2011)

Last week had similar problems with my kubota 8560. Replaced fuel filter and fuel strainer/water separator and now runs like a champ. It runs good till fuel filter starts to get plugged. Than there is nothing you can do except replace filter to get it going. So replace filter first. Than if that does not help start trouble shooting.

Oh another thing. At least with my 8560 when it coughing and running short of fuel. The computer sometimes shuts the tractor down. The fix to this is to disconnect the battery for at least 10 seconds to reset the computer.


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## davang (Apr 7, 2010)

Wethay said:


> Might be that the transfer pump outlet check valve is letting fuel flow back in. Does the transfer pump have a screen? If you have a electric fuel pump it maybe worth bypassing the fuel transfer pump temporarily. At 200 hours you shouldn't be having problems. Fuel quality may also be an issue. I'm interested in what you find.


There is an air bleeder cock at the input to the injectors which I opened to bleed and then close after 30 seconds. It is connected to a common overflow pipe above the injectors. I think it pulls air into the cylinders by the venturi effect.

Fuel pump has no screen but did make that swawku=ing sound when I had it off the tractor and pumped it manually.

The Filter/separator assembly has no screen, new filter element and is squeaky clean.

I drained the tank and using a paper shop towel as a filter had only one spec of debris come out. The fuel emptied briskly with no sign of obstruction. I shined a flashlight into the empty tank and could see no junk.

I blew out all the lines with compressed air. They were all open and again no debris came out.

So I'm suspecting either an intermittent fuel pump problem or junk in the injector pump itself.

Or something completely weird.

Oh BTW this is a 2 wheel drive manual tractor no fancy hydraulic transmission 5 years old. No Tier 4 emissions. Not sure if their is an engine computer. 40 HP.

The tractor starts right up after each stall. It has started to stall more often. The engine runs up to full RPM with good power UNTIL it stalls out. ALSO tried running it with the fuel cap loose but no change.

There's one other thing I just read. The air vent cock on the injector for bleeding air should be closed all the way after bleeding which it was but maybe there's a leak somewhere in the area. The manual says if left open tractor will stall frequently.

That's about all I can think of to fill in the blanks. Thanks for all the help!!

Jeff


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## Tx Jim (Jun 30, 2014)

Jeff

Have you considered installing an electric lift pump?

Jim


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## davang (Apr 7, 2010)

*OK PROBLEM SOLVED*

The more I thought about it, seemed like it might be an electrical problem not a fuel problem.

About a month ago I changed out the 2 suspension springs under the seat. I took one of the old ones and mounted it in the center of the platform under the seat for more support. This area is raised about 3/8" higher than where the other springs are mounted.

SO... the bottom of the seat was not depressing the OPERATOR PRESENCE CONTROL SWITCH down far enough so when I bounced or raised pressure of the seat from time to time the engine dies.

I'm about 99% sure that's it. Just ran it for 20 minutes with the arena drag no problem.

At least now I know the fuel supply is clean!


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## luke strawwalker (Jul 31, 2014)

davang said:


> *OK PROBLEM SOLVED*
> 
> The more I thought about it, seemed like it might be an electrical problem not a fuel problem.
> 
> ...


Wow... those stupid things are for lawnmowers, not "real" tractors...

I'd bypass the stupid thing myself. I hate all that safety-related crap. Sure neutral safety switches and "PTO off to start" switches are good... all the rest is extraneous junk.

First thing I do with a lawnmower is bypass all that junk that stalls the motor if you get off the seat or shuts off the motor if you try to back up with the blades in gear. Unless you're a complete moron you don't need that crap anyway... and if you ARE a complete moron it's not going to help you much anyway--you'll find some other way to kill yourself or someone else.

Later! OL J R


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## JD3430 (Jan 1, 2012)

luke strawwalker said:


> Wow... those stupid things are for lawnmowers, not "real" tractors...
> 
> I'd bypass the stupid thing myself. I hate all that safety-related crap. Sure neutral safety switches and "PTO off to start" switches are good... all the rest is extraneous junk.
> 
> ...


Smaller tractors mandated by federal laws to have safety seat switches.
Blame the nanny state, not the manufacturer.


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