A nozzle able to be arranged in a diesel injection system of the internal combustion engine of a vehicle comprises a fixed member provided with a nozzle seat at the center of which there opens a discharge orifice, the fixed member comprising a cylindrical tubular part defining an inner guide cylinder extending axially from an open first end as far as the seat that forms the closed end of the guide cylinder, and a shut-off member arranged and guided in the guide cylinder, the shut-off member being able to move between a closed state (EF) when the shut-off member is in abutment against the seat and an open state (EO) when the shut-off member opens the discharge orifice.