My guess is metering valve or plungers in inj pump are stuck. I've read where turning engine crankshaft to correct location to line up passage in inj pump so one can blow air into inj pump to free up stuck pump parts. I copied & pasted this reply from another tractor discussion forum I frequent.
[/quote]The fuel metering valve is up high and can be the first thing to dry out and get stuck. Easy to check by taking the cover off the injection
pump. If it is NOT stuck, and you think the pump plungers are stuck? Sometimes you can free them with compressed air. You just hook an air
line to an a discharge port on the pump. Them rotate the engine until that port is in "inject" position. When this is done, the compresses
air goes directly to those two plungers and will move them if possible. This is the way some of these engines are "air timed" but it works
to free stuck plungers too (sometimes). This assuming you have already followed the rules of Occam's Razor and made sure the fuel transfer-
pump is still moving fuel to the injection pump.[/quote]