A unit for supplying fuel to an endothermal engine, the unit comprising a manifold to which injectors are connected in order to supply fuel to the engine, a high pressure pumping device which has its output connected to the manifold and its intake connected to an extraction pump adapted to transfer fuel from the storage tank to this device and a pressure regulator adapted to regulate the pressure of the fuel supplied to the pumping device by supplying surplus fuel along a bleed duct communicating with the tank, the pumping device having at least one piston moving axially within a respective cylinder in order to define a variable volume pumping chamber. The supply unit has a leakage channel provided with a first mouth communicating with the cylinder below the pumping chamber and a second mouth communicating with the bleed duct, and an ejector disposed in the bleed duct at the location of the second mouth in order to recall along the leakage channel fuel leaking from the pumping chamber between the piston and the cylinder.