Abstract: A sliding vane rotary pump having fixed volume hydraulic vane actuation. The pump generally includes a rotor assembly rotatably positioned within a rotor chamber to define at least one pumping chamber. The pumping chamber is divided into a primary chamber and a secondary chamber. The axial walls of the rotor chamber define a plurality of transfer grooves and the rotor defines a plurality of rotor transfer holes. The rotor transfer holes and transfer grooves are arranged to provide a flow path from the secondary chamber to the vane slot of an extending vane each time a vane travels through the secondary chamber.