Plug pin for an internal combustion engine fuel injector nozzle

The nozzle (8) has a conical wall (13) with injection orifices (17); the pin (27) has a tip (38) activated by an axial force to engage the wall (13) and close the orifices (17); the tip (38) has a truncated-cone-shaped portion (41) having an outer surface (45) which rests entirely on the wall (13), possibly as a result of elastic deformation of the outer surface (45); and the outer surface (45) forms with the wall (13) a substantially zero angle with a tolerance of 0' to +/-10'.