no fuel to motor

[Reaper8]

Wife's car died on her today so went and towed it home and have spent the day on it to no avail. first i checked the spark and was all good there so grabbed the trusty tin of "start you bastard" and after a little spray off she went then died again. so must be fuel. noticed the pump hum to life for about 5sec when turn the key on then go's quiet ripped so out with the regulator and turned the key on. no fuel came out took the filter off and again turned the key again no fuel. The fuel pump should come on untill it builds up pressure in the line and then stop, so if i have the filter off shouldnt it flow out?? I thought there might be a blockage in there somewhere so blew the lines (both flow and return) with air. got the test light out and looked at the pump wireing. when you turn the key on the plug gets power for abou 3-5 sec only then stops. any ideas as to why (as i would think it should really have constant power at the plug without the pump hooked up) or where to look now. I have changed the pump relay under the bonnet near the battery aswell. im out of idea's and need the wisdom that is always available on this site