1994 Chevy Cheyenne Motor shuts down

Hi smitty11, Welcome to 2carpros and TY for the donation

If it feels like someone reached over and turned off the key and it fires back up right away it's the injection pump.

If the same thing happens but it has to cool down before restarting it's the PMD / FSD(pump mounted driver).

If it stumbles and than stalls then it is air in the fuel lines. If it is this one try switching fuel tanks and just turn the key to run but don't start the engine. Listen to the fuel pump for a change of noise pitch. The pump is really loud when the pump is out of fuel and will have a muffled sound when pulling fuel. Sometimes the baffle in the main tank will brake away from the tank and the pump will suck air when the tank is just off full.

Also check for vacuum lock. If the fuel tank vent is plugged air can't get into the tank to replace the fuel that's drawn out. Remove your fuel cap and see if the truck runs