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

[ljjhouser]

I will mention this, but I am sure you must have checked the water-fuel separator filter at the shut off valve. Since it recovers after a short period off, it really does sound like a fuel flow problem (or pressure). Sounds like the pressure and flow are ok for 20 min and then cannot keep up with the fuel demand. Especially since you are finding dirt in fuel system. Maybe from the take. Is the fuel bowl at the water separator not full of fuel when the problem starts? Maybe a restriction at the fuel tank outlet, if so.

 

[Garman906]

What in heck is a "rubber oil plug?"

There is a rubber grommet approximately 1 1/2 inches in diameter right behind the alternator on the left hand side of the engine.

I will mention this, but I am sure you must have checked the water-fuel separator filter at the shut off valve. Since it recovers after a short period off, it really does sound like a fuel flow problem (or pressure). Sounds like the pressure and flow are ok for 20 min and then cannot keep up with the fuel demand. Especially since you are finding dirt in fuel system. Maybe from the take. Is the fuel bowl at the water separator not full of fuel when the problem starts? Maybe a restriction at the fuel tank outlet, if so.

There is no water separator. The fuel filter w/shutoff has a sediment bowl that would trap any small amount of water. Also, I have cleaned/replaced everything from the tank to the injector pump, so there should not be any dirt or water in the system now.

 

[docone]

My best guess is that you have a fine silt or dirt in the fuel tank, ensure the tank has no debris, and next step is to ensure that your crankcase ventilation is working. that will blow the oil plug out of its hole.

 

[Garman906]

To check for a restriction, take off the left side panel and with a cold engine take out the four bolts 090 holding the muffler to the manifold flange. Clean the threads up so they turn easy and put two of them back in finger tight. Start it and run it till it starts dying, then turn it off. Loosen the two bolts a few turns, start it, and see if exhaust roars out the gap. Careful - everything will be HOT. Maybe use some sheet metal around it to avoid burning body paint.

Another idea is to take the muffler off and stand a piece of pipe in the hole instead and see if it runs better.

View attachment 746245

Tried this and when I pulled the muffler off after the bad event and it still had no power and wouldn't even pull itself up a small embankment. So it's not the muffler

 

[Garman906]

My best guess is that you have a fine silt or dirt in the fuel tank, ensure the tank has no debris, and next step is to ensure that your crankcase ventilation is working. that will blow the oil plug out of its hole.

I pulled the tank off and got a stick, fuel can nozzle and some small debris out of it. It was quite the job removing the tank. I had to cut the bracket and drill and plate it to get it back together.

 

[jshwhite]

may be time for a compression test when cold, then right after its running rough/quits.

I would agree on the compression test. It's pretty easy to remove the glow plugs on this engine. Test it cold and then when it stops running well.

How does this engine ventilate the crankcase? Does it have a pcv valve setup like the gasoline car engines used to?

Also, I think the cams and followers oil off the crankcase oiling system. I've never seen any reference to the injector pump cams having a separate oiling system.

Pretty sure the only vent on those engines is in the valve cover.
Correct, all part of the same oiling system.

I'd really lean toward fuel-starvation. I've seen filters work fine at first then plug up with 10-20 minutes of running if there's rust/silt in the system. Shutting it off lets the crud settle, then it will do it again.

Keep us posted!

 

[JWR]

Yes, in spite of the elusive nature of it I still say it is fuel issue. I don't see it being compression since compression doesn't stick around for 20 minutes and then fail... one thing that seems not to have been tried is to rig an alternate fuel source that bypasses everything else feeding right into the injection pump inlet (wherever the outflow of the lift pump goes.) May take a bit of effort but since this problem is worse than the average nuisance worth trying. I'd get some sort of fuel bladder or container, rig a fuel line from it direct to the injection pump and feed clean diesel fuel into it. May even have to rig a stand of some sort to hold the fuel bladder. Since this issue does not involve tractor motion just park it, erect a stand to hold up the bladder and let her rip. You should be able to run it for a long time in that configuration. Play with the throttle, etc. to suit yourself. If it runs OK for a good half hour you have narrowed the issue to back upstream somewhere closer the tank. Then it's a process of elimination one item at a time... not pretty but then this problem is already in the unusual catagory...

 

[Garman906]

Yes, in spite of the elusive nature of it I still say it is fuel issue. I don't see it being compression since compression doesn't stick around for 20 minutes and then fail... one thing that seems not to have been tried is to rig an alternate fuel source that bypasses everything else feeding right into the injection pump inlet (wherever the outflow of the lift pump goes.) May take a bit of effort but since this problem is worse than the average nuisance worth trying. I'd get some sort of fuel bladder or container, rig a fuel line from it direct to the injection pump and feed clean diesel fuel into it. May even have to rig a stand of some sort to hold the fuel bladder. Since this issue does not involve tractor motion just park it, erect a stand to hold up the bladder and let her rip. You should be able to run it for a long time in that configuration. Play with the throttle, etc. to suit yourself. If it runs OK for a good half hour you have narrowed the issue to back upstream somewhere closer the tank. Then it's a process of elimination one item at a time... not pretty but then this problem is already in the unusual catagory...

I would have to rig some kind of pump since the lifter pump supplies the injector pump under some level of pressure, I think. Good idea about bypassing everything. I have bypassed the filter with a small inline 36 micron universal fuel filter but that was no help and did exactly the same thing. I'll look around for an electric fuel pump.

 

[JWR]

I would have to rig some kind of pump since the lifter pump supplies the injector pump under some level of pressure, I think. Good idea about bypassing everything. I have bypassed the filter with a small inline 36 micron universal fuel filter but that was no help and did exactly the same thing. I'll look around for an electric fuel pump.

I don't think the injection pump needs any positive pressure. To my knowledge the lift pump is only there because the injection pump lacks enough "sucking ability" at its' input to guarantee continual operation when on hillsides and other odd angles. The gravity pressure from a suspended "IV drip" would satisfy the injection pump -- I'm pretty sure. There's a lot of diesel tractors out there that do not have a lift pump.

 

[seville009]

Look at post #18 in this thread - he found his problem to be a piece of cardboard for packing purposes in the fuel filter.

long shot, but worth looking at your fuel filter just to check.

Diesel runs great for 1/2 hour then very low power.

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