Embodiments of foam pumps and refill units for foam dispensers are disclosed herein. An exemplary embodiment of a foam pump includes a housing, a mixing chamber located within the housing, an inlet into the mixing chamber and an outlet valve located downstream of the mixing chamber. In addition, a sealing member movable in a first direction and a second direction is included and provided in the housing, the sealing member being movable in the first direction by pressurized air. The pressurized air causes the sealing member to move in the first direction and open a pathway for pressurized air to travel through the inlet and enter the mixing chamber. Upon a decrease in the air pressure, the sealing member moves in the second direction and closes off the inlet from pressurized air.