Starting problem?

Hi can any one help I've got an e reg ford cargo 813 horse box the problem ever time I get it stated if I leave it longer than a couple of days the fuel seems to be leaving the pump I've had the filter housing off and tested for leaks ,fine I've also changed the fuel line ,between the filter housing and the pump and fitted fuel banjos ,I'm thinking of fitting a nr next unless anybody as any idieas that would help

John
October 2013