Abstract: A detent apparatus for preventing the rotation of delivery valve holders threaded into the body of a fuel injection pump comprises a generally rectangular flat plate which is formed with substantially semicircular notches at its opposite edges for receiving adjacent ones of the delivery valve holders, respectively. A bolt is threaded into a central opening of the flat plate to abut against the top of the pump body with such a force that the flat plate is raised into pressing contact with the undersides of enlarged head sections of the delivery valve holders, thereby ensuring firm frictional engagement between the delivery valve holders and the pump body into which the delivery valve holders are threaded.