Abstract: Securing means for use in a drive coupling between rotary drive means and a tang-ended shaft of the pump of a fuel injection system, the securing means comprising a block which has (a) a hole or recess in it which provides mutually inwardly facing surfaces for engaging the opposite sides of such a tang end, or two parts of an adaptor between which such a tang end is held, (b) two laterally displaced screwthreaded bores extending from opposite outer sides of the block to the hole or recess, opening out respectively on the said mutually inwardly facing surfaces, (c) two slots each of which extends, in a plane which is transverse in relation to the respective screwthreaded bore, from a side of the block, at which the slot is open, across the screwthreaded bore and beyond it, to a closed end of the slot, stresses in the material of the block tending to shift material of the block on one side of the slot relative to the material of the block on the other side of the slot, and (d) two fixing screws which extend res