A method for controlling a pressure drop across the anode side or the cathode side of a fuel cell stack by controlling the intrusion of a cell separator into the flow channels in a feeder region of the stack so as to create a larger pressure volume on a pressure bias side of the stack. The method controls the flow rates of one or both of the cathode and anode reactant gases so as to cause the cell separators in an inlet feeder region and/or an outlet feeder region to move relative to the anode side and the cathode side so as to change a flow volume in the inlet feeder region and/or the outlet feeder region to control the pressure drop.