Have you verified how much fuel is getting from the tank to the injector pump?
Process something like remove the fuel line that goes into pump and drain tank for several minutes to see how much fuel is delivered can be used.
Is there a lift pump involved? Does it do this with the tank full or only when tank is lower than half?
Does the tractor have a water separator? Has it been cleaned? If there is one, things get clogged in the inlet side elbow.
Look at the fuel tank vent for some clog that causes a vacuum in the tank?
It certainly sounds like a fuel supply issue.
Thanks Mr. King,
I've checked the fuel delivery to the injector pump.
I failed to mention in my initial post that there is a distinct click when it stops, (I think it's the fuel solenoid), then I turn the key off and back on to start position and hear (2) clicks, one immediately, and then when I hear the second one it will start. To me, its like a relay coil is breaking down or something but thought maybe someone else had had this problem. I bought the tractor new, shop kept, and have had no problems till now.