van wont start

hi, my vauxhall combo diesel van wont start, it only cranks over. Think it may be the pump because it doesn't seem to be pumping any fuel through. Took it off but couldnt see any damage or gunk inside it. I believe its a mechanic pump so cant see how it can be an electrical fault, could it be? any other ideas? It was sitting id;le with an empty tank for 2 week so think it may have got air inside fuel system but that should have come out when i took the pump off.

thanks