Abstract: Injector (1) for injection moulding of plastic materials, comprising a body (2, 6) and a passage for running hot plastic material into the mould, an axially mobile pin (7) in the body (2, 6) for controlling said passage and a linear actuator (8) for controlling the movement of the pin (7) between an advanced closed position of said passage and a retracted open position of said passage. The injector (1) is equipped with a pressure sensor (13) detecting the pressure inside the mould, which is operative associated to said pin (7).