Abstract: A fuel injection pump comprises a housing a pump assembly mounted within the housing and an annular armature slidable within a bore defined in the housing. The armature is connected to a moving part of the pump assembly and located in the annular space between the pump assembly and the armature is an annular field assembly including a member which is supported by an end closure for the housing. The field assembly carries a winding which when energized effects movement of the armature and movement of the moving part of the pump assembly thereby to displace fuel through an outlet.