I'll back up because my words were a little harsh and might need some clarification.
On the top of the injection pump there are 6 screws that lock the delivery valves, those 6 screws are tamper proof screws, because they don't want you to take them off, the reason they don't want to take them off is because they are also an adjustment for the pump.
When you pull the delivery valves there are several fine adjustments that need to be done to get the pump in "time" or set the fuel "delivery curve", this needs to be done on a test bench, it's not something a DYI will be able to do.
Now for the real world of things, is it possible that the barrels are out of time, that's the part at the bottom that has the gears on them.
There is timing marks on the case and on the barrels, they must be aligned or it will not shut the fuel off.
If it's aligned then is the delivery pump (rod) in the right orientation, it can be 180 out and cause issues.
Don't mess with the screws or adjustments on the engine because that's not what's causing the fuel to not get shut off.
Get the pump right then is there is an issue with it running properly you can look at the other adjustments.
They normally will never be touched.