PUMPING UNIT FOR FEEDING FUEL, PREFERABLY DIESEL FUEL, FROM A STORAGE TANK TO AN INTERNAL COMBUSTION ENGINE

A pumping unit for feeding fuel, preferably diesel fuel, to an internal combustion engine (3) is provided with a hydraulic circuit (14) having a first branch (15) for connecting together a storage tank (2) and a pre-feed pump (7), a second branch (16) for connecting together the pre-feed pump (7) and a high-pressure pump (6), a third branch (18) for connecting together the high-pressure pump (6) and the internal combustion engine (3), and a fourth branch (22) which connects together the second branch (16) and the storage tank (2) and is associated with an overflow valve (27) which has a valve body (28) defined by two sleeves (30) coaxial with each other.