It depends on the lever. The fuel pump eccentric on the cam is what operates the pump and the lever arm usually has a bevel on one side and flat on the other (or a pretty obvious pad). The flat side/pad is what rides on the eccentric. Also there is a spring in the housing to keep the arm against the eccentric... so that's another tell as to which way is up.
Almost all of the AC pumps I know of ride 'on top' of the cam, not 'under' it.
