If you can see the wires/colours to the pump then they will tell you which relay it is, by having the same colour(feed one) in the relay holder at pin 87(relay output) of the relay.
Try a direct live down here and the pump will run, if ok, if not it won't of course, so then it's either a pump or wiring problem.
Relays can be troublesome on sierras, but just get a new one if needed, from auto electrical place, lot cheaper than ford, so long as terminals are in the same place and it's same or higher amperage it will do fine, does not have to be a ford one.
tabetha