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Translation: the fuel shutoff valve is electrically actuated, the assembly is called a fuel shutoff solenoid (FSS) and is located under the top cover of the injection pump (IP). Why are you asking about it, is yours bad?
Look at the injection pump, there will be two electrical connectors on its top cover, measure voltage at the one towards the front of the truck with the ignition turned on (key in "run" position) - this is the one that powers the FSS, if no voltage the FSS will not open. You can also pull the harness off that spade connector and run a jumper wire to it from the battery, you should hear a click from inside the IP when the FSS opens.
Switch is on top of the steering column shaft under the dashboard, easiest way to access it is by dropping the column down some - two bolts hold the switch, they sometimes loosen up and the switch slides down the column a bit and you can't get it to fire up the starter.