Variable displacement vane pump

A sliding vane pump comprising:

• a fixed housing defining inlet and outlet ports;
• a sliding housing defining a cylindrical chamber and configured to slide within the fixed housing, the fixed housing and sliding housing defining a side chamber;
• a rotor configured to rotate within the cylindrical chamber and having a plurality of vanes configured to seal against a wall of the cylindrical chamber to define a plurality of pumping chambers;
• and
• a spring biasing the sliding housing to a position relative to the fixed housing in which a pump displacement is a maximum;
• wherein the side chamber is fluidly connected to a first pumping chamber of the plurality of pumping chambers by a first passageway such that fluid pressure in the side chamber exerts a first force on the sliding housing, the first force opposing a second force on the sliding housing due to differential fluid pressures amount the pumping chambers;
• and
• wherein the first pumping chamber is fluidly connected to the outlet.