Injection device capable of phasing the flow rate of a gaseous fuel (l.p.g. or methane) which feeds an internal combustion engine

An injection device capable of phasing the flow rate of a gaseous fuel feeding an internal combustion engine comprises a metering valve (2) and a timed valve (3); the metering valve (2) has an inlet (11) connected to the pressure reducer (6), mechanical elements (9,10) for metering the fuel to be sent to the timed valve (3), a step motor (8) for manoeuvring the mechanical elements (9,10) according to control signals processed by a central control unit (1); the timed valve (3) presents two separate inlets (13,14) communicating with the outlet (12) of the metering valve (2), two separate outlets (15,16) respectively connected to the intake tubes (17,18) of two cylinders (19,20) in phase opposition and movable closing means (65) sensitive to the vacuum inside the intake tube (17,18) of the cylinder (19,20) in intake stroke, said movable closing means (65) being capable of intercepting the sending of the fuel to the intake pipe (17,18) of the cylinder (19,20) in intake stroke.