Remove the fuel hose connected to the injection pump beside the throttle lever, put the end of the hose in a catch can and turn on the key switch to the RUN position. Do you have a good supply of fuel from the hose?
If not, you have a plugged hose, tank outlet, filter or the electric pump has failed or not running.
If you have a good flow, reinstall the hose onto the injection pump.
Turn the key switch on to the RUN position and listen for an audible click from the fuel shut off solenoid on the injection pump every time you turn the switch ON or OFF. If you do not hear a click, see if you have battery voltage to the solenoid with the key switch in the ON position.
If there is no voltage, you will need to find the electrical failure using the schematic that is attached.
If you do have an audible click, loosen on or two of the fuel injection lines at the injectors in the top of the cylinder head and crank the engine over for a few seconds. There should be fuel squirting out around the nuts on the lines you loosened.
If there is no fuel at the loosened nuts, remove the fuel shut off solenoid from the injection pump. It is secured with two short bolts. With the solenoid removed, you would need to pull the small shut off lever on the injection pump that is next to the throttle lever, holding it until the engine dies completely.
Now, crank the engine to see if it will run after snugging the line nuts back up. If it does, you have a failed fuel shut off solenoid.
If it doesn't, you have a mechanical failure.