1998 cherokee with the 4.0L, 190,000 miles. its been starting hard, crank it for a bit and nothing, stop and try again it starts right up. when running it has about 48 psi, turn it off and the pressure immediatly starts to drop all the way down to 15 psi. It also sounds like you can hear the fuel drain pack to the tank, when listening under the hood. Should it hold the pressure after the engine is shut off?

Thanks