Patent ID: 7933712

Claim:
A defective injection detection device for a fuel injection system configured to inject fuel, which is accumulated in a pressure-accumulation vessel, from a fuel injection valve, the defective injection detection device comprising: a pressure sensor located in a fuel passage, which extends from the pressure-accumulation vessel to a nozzle hole of the fuel injection valve, and configured to detect pressure, which is fluctuated by injection of fuel through the nozzle hole, the pressure sensor being located closer to a nozzle hole than the pressure-accumulation vessel; instruction signal output means for outputting an injection instruction signal so as to instruct an injection mode of fuel to the fuel injection valve; defective injection determination means for determining whether a detected pressure of the fuel pressure sensor is fluctuated in a fluctuation mode in a range assumed from the injection instruction signal; and injection start detection means for detecting start of pressure decrease appearing in the transition waveform of the detected pressure, the pressure decrease being attributed to actual injection start, wherein the defective injection determination means is configured to determine that a defective injection occurs when determining that the detected pressure is out of the fluctuation mode in the assumed range, wherein the defective injection determination means determines that the detected pressure is out of the fluctuation mode in the assumed range when the start of the pressure decrease is not detected in a first period, which starts from an injection start instruction time point of the injection instruction signal.