in a method for operating an internal combustion engine equipped with a piston pump as a high - pressure pump , which is driven by a drive shaft of the engine , in which the high - pressure pump delivers fuel from a low - pressure region to a high - pressure side and a quantity control valve sets the quantity of fuel delivered by the high - pressure pump , the acoustic emission of the high - pressure pump is reduced by virtue of the fact that the high - pressure pump functions in a two - point operation , alternating between full delivery for individual or successive piston strokes and idle delivery for individual or successive piston strokes and , when the pressure falls below a lower pressure threshold , the full delivery is activated until an upper pressure threshold is reached .