Have an older Ferguson 35 roller with the Waukesha vrd155A Diesel in it with a stanadyne pump on it and roller will start and go to full throttle then ease down to a low idle but I have zero throttle control can see the cable is pulling on the arm but no difference in rpm I can move the second arm behind the throttle (assuming governor arm) the opposite way and it starts to kill it out and the fuel shut off on the opposite side of the pump will shut it off fine
I'm not familiar with that machine at all, but is the injector pump getting a good supply of fuel? Sounds like it may be not getting enough.
Remove the fitting from the top cover on the inj pump and then see if it throttles up.. Fuel will come out of the hole so be prepared for that..
Replaced fuel filter and it was plugged fuel could only drip out slowly starts easy now but runs at close to full throttle now and still no control of throttle