Operation of a Fuel Injection System for an Internal Combustion Engine

Operating an Internal Combustion Engine 110, comprising a cylinder 125 and a fuel injector 160, comprising, performing first and second fuel injections (preferably pilot injections) with a predetermined energizing time to inject first and second fuel quantities into the cylinder 125 that are substantially equal to each other, determining an oxygen quantity value due to the first and the second fuel injections, and determining, on the basis of the oxygen quantity value a value for total fuel quantity injected. Also determining a calculated fuel quantity dividing the total fuel quantity injected by two, determining a correction factor of the energizing time of the injector as a function of the difference between the calculated fuel quantity and a nominal fuel quantity value, and using the correction factor to determine a corrected energizing time to perform subsequent fuel injections. The invention overcomes the inaccuracy problems of the currently available strategies for adjusting pilot injections based on crank wheel information or oxygen sensors.