Your really worrying me!

That tractor does not have an fuel injection pump, it's a high pressure common rail system and is 100% electronically controlled.
Do you have Kubota Insurance on it?
If you do make a call to them and have a dealer fix it.
If you really want to do it yourself get the WSM (aka service manual) and follow it as you can so some seriously expensive damage to that tractor if you just randomly do things to the fuel system.