Try this, after it has sat overnite or for a few hours turn the key on and count to 30, then go to the start position. If it fires right up then the check valve is bad. Whats happening is that the fuel pump is refilling and repressurizing the system. Using a fuel pressure gauge that goes from 0-60 or higher lbs hook it to the schrader valve, looks like a tire valve with a cap on it, on the fuel rail, located forward of the throttle body. Fire up the engine, fuel pressure should be about 50lbs while running, shut it off, the pressure should not fall below 30PSI for 5 minutes. The check valve is located on my 98 on top of the fuel pump. While pressure may not be maintained over several hours it prevents all the fuel from emptying out of the fuel lines and the pump pressurizes that fuel much faster.
The bad news is that that pressure regulator and fuel pump are on/inside the gas tank. It's recommended to drop the tank to replace. If you do might as well do the pump also and use OEM Jeep, alot of aftermarket pumps fail pretty quickly and it's a PIA to drop the tank.
you cant see when you are about to get a mouthful of gas 
