In a method for operating a fuel injection device of a motor vehicle, fuel is conveyed under high pressure into a high-pressure reservoir, the pressure of which is controlled with the aid of a pressure regulation and from which fuel is taken for injection via at least one fuel injection valve under the control of a control device. A control pressure deviation of the pressure in the high-pressure reservoir is detected and the existence of a balance disturbance between quantity of fuel supplied to the high-pressure reservoir and quantity of fuel taken from the high-pressure reservoir is deduced from the control pressure deviation. If a balance disturbance exists, operational influencing of the fuel injection device counteracting the balance disturbance is produced and/or a corresponding report is generated.