Abstract: A combustion diagnosis device for a diesel engine having a plurality of cylinders, including an engine speed sensor for detecting a rotational speed of each cylinder, an injection correction amount calculation unit for calculating an amount of correction for fuel injection of each cylinder in accordance with the engine speed sensor, a rotational fluctuation calculation unit for calculating a rotational fluctuation of each cylinder in accordance with the engine speed sensor, and a combustion state determination unit for determining a combustion state of a determination-target cylinder in accordance with the rotational fluctuation when the correction amount calculated by the injection correction amount calculation unit reaches an upper limit threshold value.

Abstract: A combustion diagnosis device for a diesel engine having a plurality of cylinders, including an engine speed sensor for detecting a rotational speed of each cylinder, an injection correction amount calculation unit for calculating an amount of correction for fuel injection of each cylinder in accordance with the engine speed sensor, a rotational fluctuation calculation unit for calculating a rotational fluctuation of each cylinder in accordance with the engine speed sensor, and a combustion state determination unit for determining a combustion state of a determination-target cylinder in accordance with the rotational fluctuation when the correction amount calculated by the injection correction amount calculation unit reaches an upper limit threshold value.

Abstract: When switching an exhaust throttle valve from full opening to a closed position to warm up an engine, an intake throttle valve is fixed to full opening, an EGR valve is fixed to full closing, and a variable turbo-vane is fixed to a predetermined opening degree to accelerate a gas flow rate from an intake passage to an exhaust passage, a fully opened flow rate is detected and stored by gas flow rate detector, with the exhaust throttle valve being full opening. Then, an instruction is issued to the exhaust throttle valve to switch from the full opening to a closed position, after which a rotation number of the engine is detected, a threshold value is determined based thereon, a closed position flow rate is detected, a flow rate difference relative to the stored fully opened flow rate is determined, and failure of the exhaust throttle valve is judged based on whether the flow rate difference is less than the determined threshold value.

Abstract: A fuel pressure sensor diagnosing device for diagnosing a fuel pressure sensor for detecting pressure in a common rail in which a high-pressure fuel to be supplied to an engine is accumulated, the device comprising: fuel temperature detection for detecting fuel temperature; and failure determination, provided with the fuel temperature detection for detecting fuel temperature via subsequent to stopping of the engine, for obtaining a resting and stabilization time between when the pressure in the common rail drops and when the pressure stabilizes on the basis of this detected fuel temperature, detecting a stabilized fuel pressure via the fuel pressure sensor subsequent to lapse of the resting and stabilization time, and determining a failure of the fuel pressure sensor when the detected stabilized fuel pressure exceeds a predetermined upper limit threshold value or is less than a predetermined lower limit threshold value.

Abstract: A fuel pressure sensor diagnosing device for diagnosing a fuel pressure sensor for detecting pressure in a common rail in which a high-pressure fuel to be supplied to an engine is accumulated, the device comprising: fuel temperature detection means for detecting fuel temperature; and failure determination means, provided with the fuel temperature detection means for detecting fuel temperature via subsequent to stopping of the engine, for obtaining a resting and stabilization time between when the pressure in the common rail drops and when the pressure stabilizes on the basis of this detected fuel temperature, detecting a stabilized fuel pressure via the fuel pressure sensor subsequent to lapse of the resting and stabilization time, and determining a failure of the fuel pressure sensor when the detected stabilized fuel pressure exceeds a predetermined upper limit threshold value or is less than a predetermined lower limit threshold value.

Abstract: When switching an exhaust throttle valve from full opening to a closed position to warm up an engine, an intake throttle valve is fixed to full opening, an EGR valve is fixed to full closing, and a variable turbo-vane is fixed to a predetermined opening degree to accelerate a gas flow rate from an intake passage to an exhaust passage, a fully opened flow rate is detected and stored by gas flow rate detection means, with the exhaust throttle valve being full opening, after which an instruction is issued to the exhaust throttle valve to switch from the full opening to a closed position for detecting a closed position flow rate, a flow rate difference is determined by deducting the detected closed position flow rate from the stored fully opened flow rate, and failure of the exhaust throttle valve is judged when the flow rate difference is less than a predetermined threshold value.