Needle-spring locking device for pump-injectors (injectors) of diesels, in which in order to significantly increase the lift and closing pressures of the nozzle needle, the locking spring (17) is disposed in the central cavity of the body around the outer surface of the plunger’s bushing (2) and is connected with the needle (14) via a transversal cross-arm (15) disposed in the plunger bushing (2). This allows for increasing the average diameter of the needle spring (17) from 1.2-1.4 cm to 2-2.5 cm, and the spring power from 35-50 kgf to 180-220 kgf, respectively. In this case, the lift pressure of the nozzle body (10) (when the needle diameter is 0.6 cm) can amount to about 1200 kgf/cm2, and the closing pressure of the nozzle body (10) can amount to about 800 kgf/cm2, which corresponds to maximum injection pressures of 2000-2500 kgf/cm2, as required for ensuring greater fuel efficiency and lower exhaust smoke and particle matter emission in future diesels.