The injection pump is built by Bosch....but I would suspect that there isn't anything wrong with the pump. More likely there is an issue with the governor linkage which transmits motion from the throttle cable to the pump rack.
First thing is to check that the throttle lever is clamped tight on the governor shaft that goes down into the timing case. If the lever is moving but the shaft isn't turning, there will be no speed control.
Next is to remove the cover on the rear of the timing case and check the governor linkage. The most common issue here is that the return spring on the governor linkage has broken, and the pump won't return to idle because of that.
The governor linkage is very simple and usually you can see if there is anything misplaced, etc. Check the
parts book breakdown to see how things should be arranged.
DougR