have you checked for power at the pump? if no check fuse then relay.

If yes tap it quite hard with a WOODEN mallet squarely to a flat face so as not to dent it. If you are lucky it will loose off any "stiction" ( http://en.wikipedia.org/wiki/Stiction ). try it again if not try another pump.

also try listening to the pump. you should be able to hear it humming