A pump housing has a cylindrical interior surface having outlets and a pair of side surfaces defining, in combination with the interior surface, a substantially cylindrical chamber. The surfaces have inlets. A rotor has a void, lobes and, for each lobe, a throughpassage. The rotor is positioned in the chamber such that the void communicates with the inlet to receive fluid and the throughpassage for each lobe provides communication between the void and chamber. The rotor is rotatably mounted in the chamber such that the lobes traverse the cylindrical surface. Provided for each outlet is a vane. As the rotor turns, the rotor outer surface is traversed by the vane to create, as the vane traverses a throughpassage, a chamber ahead of the vane which increases in volume and communicates with the throughpassage, and a chamber behind the vane which decreases in volume and communicates with the outlet port.