The present invention provides a combined gas and liquid pump (46) for an internal combustion engine (10). The pump (46) includes a casing (58) having a cavity (60) containing a rotor (62) and a vane (64) slidably mounted to the rotor (62), wherein the cavity (60) is provided with an inlet (50) connectable to a gas source, a further inlet (48) connectable to a liquid source which is separate to the gas source, and an outlet (56). The rotor (62) and vane (64) are movable to draw liquid and gas into the cavity (60) through the respective inlets (50,48) and to move said liquid and gas out of the cavity (60) through the outlet (56). The inlets (50,48) are arranged through the casing (58) such that fluid is drawn first through one of the inlets and then through the other of the inlets before being discharged through the outlet (56).