close off the pump lines below the head. fill the cap with cleaning solution and repark the heads over the caps. are you sure that you are getting vacuum at the cap? inspect for ink on the gears (failed pump tube). disconnected pump line. clogged pump. complete loss of black is rarely a head clog. clogged heads will print terrible test patterns ... but will print at least a couple lines of black. disappearance of black is usually empty dampers (disconnection, air leak, etc), or disappearance of vacuum thus not priming the heads with ink.