If you still have the old relay, carefully remove the plastic cover. Place the relay back into the socket in the UEC and manually actuate its armature to close the contacts. With the engine off, you should be able to hear the pump running and measure fuel pressure.
If this works, you can consider the pump and all it power wiring to be intact, and focus on the control side, including the ignition reference as aleekat suggested, and the PCM and its wiring.