Abstract: An inkjet printer, utilising at least one ink reservoir having a pump chamber, includes an ink pumping mechanism for pressurising the chamber, the pumping mechanism including an actuator that is biased to pressurise the chamber and that is acted on by a cam to release the pressure. The actuator can include an opening through which the camshaft extends, and the cam can be accommodated within the opening and can engage a cam follower formed on an inner wall of the opening. The bias may be a compression spring mounted in a drop-in manner within a guide element for the actuator. The cam and spring can act directly on the actuator, and a single actuator element can pressurise the chamber, act as a cam follower and include an out-of-ink trigger thereon.