Abstract: Apparatus for controlling the quantity of fuel injected per shot or the beginning of fuel injection in a diesel engine comprises a control rod, which is adjustable by a stepping motor through the intermediary of a resiliently yieldable coupling. The control rod acts to control the injection pump or pumps. In order to provide a structurally simple apparatus which comprises a low-power stepping motor and to eliminate backlash between the cooperating elements of the apparatus, the shaft of the stepping motor carries a camwheel, which is indirectly engaged by the control rod, which is biased by a spring. The resiliently yieldable coupling can be coaxial with the camwheel and adapted to rotate as far as to stop only in one sense of rotation whereas the coupling is rigidly connected to the camwheel for a movement in the other sense of rotation.