FUEL PUMP FOR A DIRECT INJECTION SYSTEM

Fuel pump (4) for a direct injection system provided with a common rail (3); the fuel pump (4) has: a pumping chamber (14) defined in a main body (12); a piston (15) which is mounted in a sliding manner inside the pumping chamber (14) to cyclically vary the volume of the pumping chamber (14); an intake channel (17) which originates from a wall of the pumping chamber (14); an intake valve (18) which is coupled to the intake channel (17); a delivery channel (19) which originates from a wall of the pumping chamber (14); a delivery valve (20) which is coupled to the delivery channel (19); and an actuating spring (16) which has a plurality of turns (26) having a pitch (P) between the turns (26) being variable and coupled to the piston (15) so as to push the piston (15) towards a maximum volume or minimum volume position of the pumping chamber (14).