Ok so the pump is getting voltage when you turn it over.
From memory the ecu gets a signal from the CPS which will prime the pump etc...
I would "assume" that if it was getting voltage when your turning it over that this part of the cycle is ok. As you have said checking the relay that controls this is a good idea, but it must be working before it's getting the 12.7 volts as it's activated as soon as the ignition is switched to pos. 2 and when you turn the engine over.
Also when you crank it over next time, pull out one of the sidelight bulbs, bend the little contacts and plug it into one of your injector connectors on the loom, you should see the bulb flash to indicate that the injectors are getting power, and therefore opening to let the fuel in.
It's starting to sound to me that it's not a problem with your fuel pump or pump wiring, but something elsewhere, I could be totally wrong tho....