If you identify the relay for the pump, look at it's terminals, number 30 or 30/51 is power input from battery/fuse, no 87 is the output, so if putting a live down here starts the pump it gets you a lot nearer, then see if it is lack of feed to relay from fuse/battery, lack of earth at relay(85) or lack of switching signal to energise relay(86).
NB some makers get mixed up over 85 and 86, makes no difference it works eithe way round as it just causes a magnetic pull inside relay to pull contacts closed.
tabetha