Abstract: A pump/nozzle unit having a piston injection pump and an injection nozzle which includes a pump piston that is driven via a drive tappet and is rotatable via a regulating sleeve. The regulating sleeve is inserted into a recess on the end face of the pump housing and is axially secured in its installed state by means of a guide bushing. The guide bushing comprises a guide part for the drive tappet and a flange radially protruding beyond the outer diameter of the tappet spring, the flange being secured on the pump housing by a holder mechanism. The forces exerted upon the pump/nozzle unit during operation are absorbed by a securing arrangement.