Piston pump with pump inlet check valve

A piston pump comprises cylinder attached within a cavity of a pump housing. An outlet check valve seat is defined about an outlet of the cylinder. A piston is slidably received in a bore of the cylinder and has a first passageway formed therein. A cylinder head encloses the outlet of the cylinder and defines a second passageway therein. The first passageway has an inlet in fluid communication with the cavity of the pump housing, and an outlet in fluid communication with a pumping chamber defined in the pump housing. A first spring retains the piston to the cylinder. A first check valve member is a ball retained near a valve seat formed in the first passageway of the piston by a disk spring, and allows fluid to flow only from the inlet to the outlet of the piston.