Fuel injector

A piezoelectrically actuable fuel injector comprising an accumulator volume (36) within which a piezoelectric stack (40) is arranged, the accumulator volume (36) being arranged to receive fuel from a source of pressurised fuel, in use. The piezoelectric stack (40) carrying an end member (48) which engages a surface associated with a piston member (24) so as to apply a retracting force to the piston member (24) upon a reduction in the axial length of the piezoelectric stack (40), the piston member (24) being operable to control fuel pressure within a control chamber (18). A volume (50) is defined between the end member (48) and the surface associated with the piston member (24). The volume (50) is provided with vent means (63) to permit fuel within the volume (50) to flow to a low pressure drain.