Patent ID: 7444993

Claim:
A method for monitoring the operability of an injection system of an internal combustion engine, comprising a pressure accumulator, an injection valve connected to the pressure accumulator, a controllable fuel supply system which delivers fuel to the pressure accumulator, the method comprising the steps of: measuring the pressure in the pressure accumulator by a pressure sensor coupled with the pressure accumulator, feeding the measured pressure value to a control unit; controlling the quantity of fuel delivered by the injection valve and supplied from the fuel supply system as a function of operating parameters of the internal combustion engine, varying the quantity of fuel delivered by the injection valve, measuring a resulting pressure, comparing the resulting pressure with a setpoint pressure for the given operating conditions, and detecting a malfunction source depending on the deviation of the measured resulting pressure from the comparison value and if the measured resulting pressure is below the setpoint value, wherein in case of a change of injection quantity, a pressure valve connected to the pressure accumulator which cannot set the desired pressure is detected as the source of a fault, if the pressure is below setpoint in the pressure accumulator, and in case of an approximately constant pressure in the pressure accumulator.