Fuel injector for internal combustion engines

An automotive piston engine has a fuel injection pump with a housing (1) incorporating a sliding piston-shaped needle (12). Longitudinal movement brings the needle into contact with a valve seat (15), thereby regulating the fuel injection aperture (17, 18). The housing (1) further incorporates a sliding sleeve (30) in permanent contact with the valve needle (12), the other end of the sleeve forming a seal to an inlet passage (40). The sleeve (30) incorporates a longitudinal channel (38) terminating at one end in the inlet passage (40) and at the other in a fuel flow passage (22) in the needle to the jet outlet. The housing incorporates an adjustable pressure fuel flow regulation chamber (42), the pressure regulating the valve needle closing force.