A system ensuring sealing and preventing outlet of hydrocarbons in capless gasoline onboard refueling vapor recovery systems comprises: • a front body guiding the nozzle during fuelling and preventing outlet of excess fuel, • a primary flapper allowing opening and closing of the outer nozzle receiver opening by moving together with the cap, • at least one spring-1 allowing the opening and closing movement of said primary flapper during fuelling, • an outer body , • a secondary housing connected to said front body and removed from the outer body when there is an impact on the front body , • at least one pin fixed on said secondary housing so as to allow movement of said primary flapper around the axis thereof during opening and closing movements, • a nozzle guide guiding the nozzle during fuelling, • a plunger that allows air intake from outside, by coming to a lower position when the air pressure is reduced in filling tube , • a valve cap that keeps the plunger in a cylinder during movement, • at least one spring-2 that is compressed or loosened according to the movement of the plunger characterized in further comprising: • at least one lever primary allowing equal distribution of the compression load of said spring-1 to all sealing areas via at least one spherical joint, improving sealing; • a wave seal ✔ preventing outlet of hydrocarbons by means of surrounding the nozzle while the nozzle is being placed, ✔ allowing uni-directional flow to continue and preventing backflow when there is pressure in the opposite direction from within, ✔ allowing the fuel to exit through the filler neck by being bent outwards. • a front body guiding the nozzle during fuelling and preventing outlet of excess fuel, • a primary flapper allowing opening and closing of the outer nozzle receiver opening by moving together with the cap, • at least one spring-1 allowing the opening and closing movement of said primary flapper during fuelling, • an outer body , • a secondary housing connected to said front body and removed from the outer body when there is an impact on the front body , • at least one pin fixed on said secondary housing so as to allow movement of said primary flapper around the axis thereof during opening and closing movements, • a nozzle guide guiding the nozzle during fuelling, • a plunger that allows air intake from outside, by coming to a lower position when the air pressure is reduced in filling tube , • a valve cap that keeps the plunger in a cylinder during movement, • at least one spring-2 that is compressed or loosened according to the movement of the plunger • at least one lever primary allowing equal distribution of the compression load of said spring-1 to all sealing areas via at least one spherical joint, improving sealing; • a wave seal ✔ preventing outlet of hydrocarbons by means of surrounding the nozzle while the nozzle is being placed, ✔ allowing uni-directional flow to continue and preventing backflow when there is pressure in the opposite direction from within, ✔ allowing the fuel to exit through the filler neck by being bent outwards. ✔ preventing outlet of hydrocarbons by means of surrounding the nozzle while the nozzle is being placed, ✔ allowing uni-directional flow to continue and preventing backflow when there is pressure in the opposite direction from within, ✔ allowing the fuel to exit through the filler neck by being bent outwards. <EOS>