In case you do not get fuel at the injectors, check the fuel delivery from the tank forward.
- get a cheap pressure gauge that screws into a 1/8 in NPT port. There is a square plug on top of the tank where the fuel pump sits. You can put the gauge in place of that plug. With the accessory switch on and the in-tank pump running, you should see around 7-9 psi there.
- put the gauge into the port above the secondary fuel filters on the driver side on the engine. With the engine running, you should see around 70 psi. Not sure what you should see with the engine merely cranking. Probably less but the pressure should be way up from the 7-9 that the in-tank pump delivers. You did say earlier that you get fuel at the secondaries...good, but is it at pressure?
If there is not enough pressure at the secondaries, take the primary filter off (passenger side frame rail, underneath the alternator) and replace. Also, if you see any gunk at all in the fuel lines when you take plugs out, it would be good to blow the lines out with compressed air. Blow them from the front to the back...gunk should go towards the tank, not into the injection pump.
Now what?
If you have pressure at the secondaries when cranking at a good clip and she still does not have fuel at the injectors, the next step is the hydraulic head of the injection pump. There is a hex plug in the top of the hydraulic head. When you take that out, put a pencil or wooden dowel into the hole. Pencil/dowel should move up and down at least 1/4 inch when the engine spins over. That means the plunger in the hydraulic head is indeed working and not stuck.
You said that you verified the shutoff to be working; the next suspect is the "button" at the bottom of the hydraulic head that might have fallen off. To check that, the hydraulic head has to come off.