have you tried locking the pump on by by-passing the relay? not sure what pins on your car it'll be but the haynes manual should tell you if you've got one. that way you can find out if its the relay/relay connectors or not.

You can test the relay by finding out which side is the trigger and which is the switch. To test the trigger you can apply 12v and listen for a click. To test the switch you need to test for continuity when the trigger is activated, you can do this using a multimeter or a test lamp if you've not got one.

If you dont already have a multimeter i suggest you go and buy one. even maplins cheapest and shittist is better than none.

JAmes.