A pump apparatus, which comprises: a tubular portion comprising an electroactive polymer actuator that expands and contracts an inner volume of the tubular portion based upon received control signals; and a control unit electrically coupled to the electroactive polymer actuator and sending control signals to the actuator. The invention is characterised by a valve body arranged interiorly of the first section and configured for optionally allowing blocking of the passage in a first position and of the opening in a second position. , for a vehicle fuel cell system, which can efficiently supply hydrogen to a fuel cell stack and increase the efficiency of an ejector.