Abstract: To provide for accurate alignment of a housing (10) retaining a fuel injection element (12, 15), and a second housing (23) retaining a control element controlling a function of the fuel injection element, in which the relative positions of the pump housing (10) and of the control element housing (23) are determinative of adjustment and alignment of interengagement between the injection element and the control element, the two housings are provided with attachment screws to attach them securely together, while permitting respective removal, for example for replacement of a sealing gasket (26), and to insure precisely aligned re-assembly, the housings include position locating means (27-34, 35') such as interengaging projection-and-recess means (40, 50, 60, 70, 80, 90, 100, 110; 37, 47, 57, 67, 77, 87, 97, 107) which accurately position the housings with respect to each other, and which are positionable after the housings have been first assembled and aligned to provide for said adjusted and aligned interengage