Pre-controlling process of a variable lift fuel pump in an Internal combustion engine

Process for pre-controlling a reciprocating fuel pump of a vehicle comprises from the starting values determining the fuel volume removal from a high pressure rail by the injection valve per stroke of the pump, determining the fuel volume necessary for a change of theoretical pressure in the high pressure rail per stroke of the pump, and determining the volume loss by a non-optimum degree of delivery based on the formation of steam bubbles in the fuel. Preferred Features: The reciprocating pump is driven by a camshaft of an internal combustion engine.