Kubota L3710 runs for 20 minutes then won't run at speed or at all.

[Garman906]

I have not been able to try the JWR method yet, but I do agree it would be a good thing to do. I'm trying to rig up an alternate tank/source. I also ordered a small electric low pressure, low volume pump to force feed the injector pump. I'm going to have a million dollars tied up in this project. Might be better off to buy a new tractor. haha

 

[Garman906]

I read all of the posts and am curious about a couple of points. I have an L3710 - really like it. The fuel tank is at hood level, behind the instrument panel. Maybe I haven't researched enough, but I don't think I have an electric lift pump for fuel. The tank is above the injector, so my expectation is fuel is gravity fed to the fuel filter then into the injector. If air is introduced, then the injector is sucking, and that sucking means fuel restriction.

Now my main question - you have stated that you have drained the tank more than once. What is your definition of drained? Did you remove the tank to drain, or only use the tank outlet with the tank in place? if you have not removed the tank, I believe it is time. The fact that you have removed debris from the tank reinforces the suggestion. I have many experiences with tanks that get plugged at the tank outlet. Sometimes there is a screen, sometimes not. The remedy is removal and disassembly of the outlet fixture/connection. I wash the tank out with a garden hose then let it dry before reinstalling. A shop vac hose in the empty tank helps drying.

I have drained the tank on the tractor and I have removed the tank and sloshed diesel fuel around in it and turned it upside down to drain any debris through the gauge sender mounting hole. I removed the sending unit because the filler spout on the tank has a ledge around the opening about 3/4 inch down from where the cap fits on that would prevent debris from falling out.

 

[Skystream]

The best advice I can provide is to take points out of the equation. Definitely sounds like a fuel delivery problem. The post of rigging up a temporary remote tank is the best starting point. Just have to make sure you provide for a fuel return line to tank. A collapsed fuel line typically is due to a restriction upstream unless the line is non OEM and possibly has weak walk support.
Assume that you cleared flexible lines with compressed air back towards tank starting at injection pump supply side by detaching lines. We know not to blow through low pressure mechanical pump and or filter.
Have had previous issue with low pressure pump leaking at seal allowing air to enter system. Determined it to be case by slight vacuum pump test across ports or temporary clear line on output port looking for bubbles.
Still believe it's the low suction port of fuel tank. Have seen in Kubotas many times...a floater. One time it was a small plastic disc that moved around in the tank until just the right moment and was sucked down covering the suction port .
A flexible remote camera helped us alot in fuel tank issues.
Hope this helps.....good luck!

 

[ruffdog]

A small auxiliary fuel tank is common when tuning motorcycles, outboards, etc. and should feed the injector pump fine. UNLESS.....I wonder if the inlet to the injector pump has some gunk in it that moves around?????

https://www.amazon.com/ALPHA-MOTO-M...6&sprefix=auxillary+fuel+tank,aps,1319&sr=8-5

Motorcycle Auxiliary Fuel Tank Gas Tank Carburetor Carb Tuning Plastic Bottle | eBay

 

[JBF43]

A friend of mine called me a few years ago with a similar problem on an older Kubota. I had no clue so looked on the internet. Said it was either overheating or gas in the diesel fuel. I could not see any water in the radiator, but that did not help. I smelled the fuel and could detect a gas smell. He insisted it did not have gas in it. He finally drained the fuel out and put new Diesel fuel in and it ran fine. He still was not convinced so he put the old fuel in his diesel lawn tractor.Thirty minutes later it shut down just like his tractor. you may have already put fresh fuel in but I did not see it in your post. good luck.

I had that exact same thing happen on mine right after Hurricane Michael came through here in 2018. It would run great for a bit, then power way down and sometimes even quit, then it would make that same 'come back'. Pulled the bowl and smelled the fuel. Sure enough some gas in there. Drained the tank and replaced with new clean diesel, never had a problem since.

 

[Garman906]

A small auxiliary fuel tank is common when tuning motorcycles, outboards, etc. and should feed the injector pump fine. UNLESS.....I wonder if the inlet to the injector pump has some gunk in it that moves around?????

https://www.amazon.com/ALPHA-MOTO-Motorcycle-Professional-Compatible/dp/B004NV42PQ/ref=sr_1_5?crid=1JZ7IBUSLYDRN&keywords=auxiliary+fuel+tank+motorcycle&qid=1653138546&sprefix=auxillary+fuel+tank,aps,1319&sr=8-5

Motorcycle Auxiliary Fuel Tank Gas Tank Carburetor Carb Tuning Plastic Bottle | eBay

I'm wondering about the injector pump myself.

 

[Garman906]

I had that exact same thing happen on mine right after Hurricane Michael came through here in 2018. It would run great for a bit, then power way down and sometimes even quit, then it would make that same 'come back'. Pulled the bowl and smelled the fuel. Sure enough some gas in there. Drained the tank and replaced with new clean diesel, never had a problem since.

I just replaced the filter assembly and fueled up with 5 fresh gallons of diesel. We'll know in a little bit.

 

[airbiscuit]

I had a friend that had a similar problem. Turned out it was algae in the fuel, but it sounds like you have cleaned out everything pretty well.

 

[Garman906]

Ok, I went out after lunch and ran the tractor with bush-hog for 30 minutes solid on some pretty rugged terrain and it appears that the problem is fixed. The tractor ran and sounded like it used to. The only thing I did since the last episode is I changed the fuel filter assembly, rechecked all the hose clamps for tightness, refilled the tank with fresh diesel that I just purchased yesterday, and added sea foam diesel conditioner (highly recommended by the Kubota mechanic). I really think that I just had a bad batch of fuel. The fresh fuel that I had previously put in was from last summer and obviously there was something wrong with it.

I appreciate everybody's help and suggestions and I hope that this will help somebody else with similar problems.

I told the wife that it would be a really simple fix and that I would be embarrassed. I was right.

 

[thclimer]

Ok, I went out after lunch and ran the tractor with bush-hog for 30 minutes solid on some pretty rugged terrain and it appears that the problem is fixed. The tractor ran and sounded like it used to. The only thing I did since the last episode is I changed the fuel filter assembly, rechecked all the hose clamps for tightness, refilled the tank with fresh diesel that I just purchased yesterday, and added sea foam diesel conditioner (highly recommended by the Kubota mechanic). I really think that I just had a bad batch of fuel. The fresh fuel that I had previously put in was from last summer and obviously there was something wrong with it.

I appreciate everybody's help and suggestions and I hope that this will help somebody else with similar problems.

Looks like your effort payed off!!

It certainly could have been a number of different things, but I'd guessing bad fuel that junked up your filter.

Glad to hear she is running back like she used to.