First off, you said you took the cap off the fuel rail nipple, did you depress the little valve inside? It is like a tires shrader valve and needs to depressed to emit any fuel. Second when you turn the key to run position or the normal position after you started the jeep can you hear a whine from the fuel tank area? do this several times then try the fuel rail valve. The system (pump)will charge the fuel rail then turn off.
If you don't hear the pump whine for a few seconds then check the fuse for the fuel pump, This is behind the glove box. the fuel pump relay, is under your hood next to the battery in the engine compartment.
If both are ok then it is eight bolts/ 3 or so hours to replace the fuel pump. As pointed out you will need to drain the tank to get to the fuel pump. There are two fuel strainers that should be replaced as well to get the MFG warranty on the fuel pump.
My guess is that you just filled the tank recently for it to be full as you stated. 99% of the time the fuel pump dies just after filling the tank. And unfortunately they give little to no warning before they go. Older diaphragm types (mechanical fuel pump) used to weaken and give hard to starts in the winter time due to the rubber shrinking in the mechanical diaphragm. The drop in tank types are a offset vane type that just stop spinning inside when they die.
