Fuel supply system (1) for a combustion engine, which includes a fuel tank (2) suitably supplied with a fuel filter (3) and a duct (4), which connects the fuel tank (2) with a fuel supply unit (5), for instance a carburetor or a fuel injection system. A pressure regulator (6, 7) is, rigidly or flexibly, mounted to one side of the tank (2), suitably the upper side, and is immersed, entirely or mainly, in relation to the tank side, and the pressure regulator is connected somewhere in between the duct's (4) inlet inside the tank (2) and its outlet out of the tank.