An embodiment of a direct injection assembly of the common-rail type provided with a fuel tank, a manifold, a high-pressure pump for feeding the fuel to the manifold, a low-pressure pump provided with an intake pipe and connected to the high-pressure pump by means of the intake pipe to feed the fuel taken from the tank to the high-pressure pump; and a shut-off valve of the ON/OFF type which is arranged along the intake pipe to adjust the delivery of the fuel fed to the high-pressure pump; and a pressure regulator, which is arranged along the intake pipe immediately upstream of the shut-off valve to keep the pressure of the fuel inside the intake pipe under a predetermined value.