The control rack on the injection pump is stuck.. possibly from old fuel..
Is there a removable plate below the inj. pump ?? remove it & see if u can get your fingers on the control rack..
Does the engine shut off w/ a pull cable or the key switch ??
If its w/ the key, theres an electric shut off solenoid that might screw into the block.. u can unscrew it and get your finger in the hole..
The inj. pump will probably have to be removed to fix the problem..