Need help! GR2100 diesel won't run

[Joe.M]

2007 GR2100 diesel. A few days ago the tractor would start hesitating in rpms when under load. All the sudden it's now only running at a very low rpm and the throttle won't do anything. Assumed a fuel issue. Replaced both front and rear fuel filters, bled fuel lines at injector pump and by loosening the injector lines and turning the key. Seems like I got the air out and it's still running the same, just a low rpm with no throttle response. Drained most of the fuel tank and put in new diesel, with a bunch of additives in case it was something in the fuel. Same issue and I let it run for a few minutes hoping the new fuel would feed in but it still may have not. Fuel filters/lines prime fine. Fuel sprays out of injector pump and injector lines fine, so doesn't seem like a fuel pressure issue. Not blowing any smoke.
I am not familiar with diesels so not sure what else may be wrong.

 

[Roadworthy]

Have you checked or cleaned your air filter? Be sure the path from there to the intake manifold is clear.

 

[lmichael]

Diesels will run as long as there is sufficient fuel and air. If there was insufficient air flow (as in clogged air filter) black smoke would be prevalent. So my thinking is you have a fuel flow issue. I'd be looking for a collapsed fuel line, a bad lift pump, or something allowing air into the fuel system (though that might present differently than what you're seeing). I'm putting my $$$$ on insufficient fuel flow

 

[Mark_BX25D]

Could also be something in the tank blocking the outlet. That's why some of us like coffee filters.

 

[Joe.M]

Air cleaner is very clean and nothing restricting it from what I can tell, I doubt that is the issue. As far as fuel flow from the tank, it drains out fast...I drained the tank to put in fresh diesel and it poured out, no restriction from my point of view and no discoloration or sludge. Also the low pressure pump visually fills the filters quickly as it probably should. I just took off the injection pump and the roller springs are very firm...I saw a video online of someone showing 1 of their internal springs was broken causing that cylinder to not get the right fuel/fuel at all. I bled the air out again after reinstalling the injection pump and let the pump squirt fuel out of the loose lines right at the injectors and that's fine too. Also, I ran the injection pump with no outlet lines to make sure it was pumping all 3 lines and it squirts out far as it should. Now with everything back together it won't even start.
I went to my local Kubota dealer today and talked to them about it and with everything with the fuel working after my experimentation it may be bad injector(s)?

 

[Dieseldonato]

Its rare for a complete set of injectors to go bad at once. I would say something in the govenor has gone bad, but it's very hard to diagnose with out being there.

 

[Joe.M]

After working on the engine most of the weekend I'm down to there being air in the fuel system. I did bleed at the injector pump bleeder and at the injector lines. There still may be more air in the lines to the injectors but it takes a lot of cranking to fill the lines up and I don't want to overheat the starter. Are there any special tips on how to bleed the system? In my mind there should be a somewhat easy way to bleed the lines since replacing fuel filters is standard maintenance and that's what initially caused me to get air in the lines.

 

[lmichael]

The lift pump should be able to do the trick