Abstract: A positive displacement shuttle pump having a cylinder with axially displaced and mutually isolated inlet and outlet portions; a shuttle piston having a reservoir for accepting pressurized feed from the inlet port in the feed cycle and for dispensing feed to the outlet port in the dispensing cycle; a displacement piston extending longitudinally in the shuttle piston and communicating with the reservoir; an actuator for extending the displacement piston into the reservoir to pressurize the feed and urge the feed through the outlet port during the dispensing cycle; the displacement piston is responsive to the pressurized feed in the reservoir for retracting during the feed cycle; the displacement piston driving the shuttle piston through the feed and dispensing cycles.