2000 xj fuel issue

ive got a 2000 cherokee with the 4.0 and auto trans. The jeep died while driving, and i had it towed home. When you turn the key on the fuel pump runs for a few seconds, but quits. If i hold open the scrader(sp) valve while cranking it only pumps fora few seconds then stops. I replaced the pump and filters and still have the same problem. what could it be? The jeep will start off of ether but will die when it burns up all of the ether, so it has spark. is there some sensor that could be causing this?

That's how the fuel pump works until the car is running. You turn the key and the pump primes the system for a couple seconds, then shuts off. Shooting in the dark of course, but I would start thinking crankshaft position sensor. Sometimes unplugging it and plugging it back in will give it a kick in the pants to get it started, although if this works, it should be replaced.

usually if the CPS fails, you won't have fuel or spark. As he's got spark, I'd look at the fuel pump relay as a candidate. Swap it with the AC relay Assuming you've got AC) and see if the pump runs then.

i have swapped relays with the starter relay, and no go. i know that the pump runs only for a few seconds, but while cranking it should continue to run while the line if off or valve is open because the pressure hasnt been acheived to kick it off.