Described is an ink delivery system for an inkjet printing system including a housing; a printhead fixed to the housing for ejecting droplets of ink on media; a regulator located within the housing; a source of ink for replenishing the printhead; and an ink passageway for connecting the source of ink and the valve inlet. The regulator including a valve having an inlet and outlet, with the outlet in fluid communication with the printhead; a flexible member within the print cartridge, the flexible member has a reference surface and an ink surface, the reference surface is in communication with an outside atmosphere, the ink surface is in fluid communication with the printhead, the difference in pressure between the outside atmosphere and the printhead causes the flexible member to bias toward the ink surface; and an actuator that is receives a force from the ink surface of the flexible member, the actuator actuates the valve based upon the differential pressure between the reference surface and the outside atmosphere. Also described is a fluidic coupling that releasably and fluidically connects to the inlet port of a print cartridge. The fluidic coupling acts as a seal for the print cartridge and a means of lubricating and protecting the inlet port from drying, leaking ink, and air ingestion while the print cartridge is in transit and in storage. The fluidic coupling also provides an auxiliary ink reservoir for the print cartridge. The fluidic coupling further provides an ink conduit to the printhead from an external ink supply.