Kubota diesel won't stay running

Help, I am working on a friends 3 cylinder Kubota L2600DT tractor. It had been sitting outside for 2 years with busted hydraulic hoses.

I fixed the hoses and changed the fuel filter and oil and filter. Put fresh diesel in it and fired it up. At first it would start and run a few seconds and die. Then I discovered a black thumb screw on the injector pump. It was closed and when I opened it (turning counter clockwise), then the tractor ran OK.

But today on a test drive after about 10 or 15 minutes it started bogging down and the exhaust started getting black. It finally quit running. It will start and die over and over. I checked the little thumb screw on the injector and cannot detect a difference in changing the setting.

Also, it sounded like an injector knock from overfuel when it was last running. At least that is what I suspect. It has enough oil and the light is not on so I think the oil pressure is OK.

I opened the bleed screw on the fuel filter and clean fuel comes out.

Does anyone have an idea what could be the problem? I have no manuals or even any experience on this model tractor. Never had anything like this on my other diesels.

Thanks for the help.

On my skid steer with a Kubota, that thumb screw is to help bleed the fuel system. Turn it out to bleed and after the engine is running smooth, turn it all the way in. You should have at least consulted a manual or called a dealer. You could have even asked on here. Kubota's aren't exactly a rare engine. Hopefully you haven't done any serious damage. Dave

Just a guess, but you may need to replace fuel filter AGAIN, bleed the fuel system again. Nasty crud could have built up in fuel tank during storage.

Update--after sitting overnight, I started the tractor again. Now there is a lot of black smoke and there does not seem to be any throttle response. i.e. when you advance the throttle, the engine does not speed up.

I can hear a "hiss" from the exhaust. The linkage to the injector pump is intact and visually everything seems to be working as it should. Is it possible the muffler could be somehow plugged up to cause this kind of situation? I did check the air filter again and that is clear.

I turned the bleed screw on the injector pump closed and open and no change in how it runs.

All ideas appreciated. Thanks.

It sounds like you have an air restriction. Black exaust indicats that. There is no lack of fuel and that screw is a bleeder as mentioned, and should be shut.Check the air intake area, and the filter for blockage caused by critters or wasps that could restrict air flow into the manifold. Remove the air cleaner pipe from the intake manifold and see if it runs ok.If it does remove the restriction between that pipe and where the air enters the air cleaner. You never mentioned servicing the air cleaner.If you do install a new air cleaner element, make sure you remove the protective plastic shipping film covering the element.Good luck

The problem is resolved. It was the muffler and it was totally blocked with carbon and rust.

I ended up taking it off and banging in around and getting as much of the stuff out as I could. It has screens in both the inlet and outlet ends. They looked kind of restrictive even if they weren't carboned up. So I just punched them out.

Reinstalled the muffler and riser pipe. Tractor is just as quiet as before and runs great now.