Abstract: A rotary pump such as a rotary fuel injection pump comprises a pump body; a rotor rotatably supported by the pump body and responsive to mechanical pulses to pump a fluid; and a stator ring (208) supported by the pump body and having a ring of projections (209) arranged to deliver mechanical pulses to the rotor when the rotor rotates relative to the stator ring. The stator ring (208) has a vibrational mode which is induced by delivering the mechanical pulses to the rotor. The pump body supports the stator ring across an interface which is a complete annulus or a partial annulus. In order to reduce the transmission of vibration from the stator ring to the pump body, the interface and/or stator ring incorporate cavities at the antinodes of the vibrational mode of the stator ring.