The invention relates to a method for starting an internal combustion engine associated with means for adapting, during an engine start operation, an amount of fuel injected based on an estimation of the volatility (PVR) of the fuel based on the comparison between a gradient of the engine speed measured upon a preceding start operation and a reference gradient (110) corresponding to a predetermined fuel, characterized by the step (111) of correcting the reference gradient based on a change (ΔCMF) in the engine friction torque.