starting my ldv pilot?

We've expierienced problems with starting our van, we assumed it was a fuel filter problem, so we changed the filter and seals and 'o' rings. We bled the fuel system via the bleed nipples and started the van. It fired up first time, but the engine died moments later. We checked the bleed nipples again and air was present in the fuel. We are sure as we can be the filter was tightened correctly and the seals were all in place. Could the fuel primer pump be faulty, or is it something else? I would be greatful for any help offered. Cheers , Paul.