92 f-150 problems with truck shutting off
 

92 f- 150 FD<S or fuel pumps in each tank. Truck idles for 1-2 minutes and shuts off on either tank. Fuel pump run in each tank all the time depending on which tank is turned on. I replaced fuel pressure reg. with new one, tried clamping off fuel lines and return lines to each tank, truck still stops after 1-2 minutes, truck is hard starting on either tank after stalling once started truck seems to run o.k. at the mid to rull rpm.

Could you clarify something, do the fuel pumps run ALL the time even when the engine isn't running?
Do you know where the fuel pump relay is located?

Did you run a pressure/volume test at the fuel rail schrader both prior (on start up) and during a stall monitoring the pressure and volume to verify the drop?

92 f-150 problems with truck shutting off
 

with just the key on, the pumps run, and sometimes not. I do not know where fuel pump relay is located, book did not show it.

obviously there is insufficient pressure to the injectors, because there is a check valve somewhere on fuel delivery mod, in one of the tanks? or somewhere else.

If you have access to a fuel pressure gauge, jump the DLC on the 'fuel pump' connection and ground the other end. You should hear the fuel pump relay 'click' and the pump/s will run continuous as long as the key is ON. If the relay clicks and the pump/s don't run, look for 12V through the inertia switch. If no voltage there, check the relay again. If all the voltages prove out, make sure there's enough pressure and volume at the schrader/rail when jumped. Grounding the DLC will also take the PCM out of the diagnosis and helps to prove out the circuits for voltage distribution.