Failure diagnosis device for fuel supply system of direct injection internal combustion engine

摘要

PROBLEM TO BE SOLVED: To diagnose a failure of a relief valve during the operation of a high pressure pump.SOLUTION: When a failure diagnosis execution condition of the prescribed relief valve 33 is satisfied at the start of an engine or during the drive of the engine, target fuel pressure Pftg in a high pressure fuel system is set higher than relief pressure Pfrl, and fuel-pressure forcible rise control for controlling the high pressure pump 14 is performed so as to make fuel pressure Pf in the high pressure fuel system reach the target fuel pressure Pftg. After the lapse of a prescribed standby period KT1 after the fuel pressure Pf in the high pressure fuel system reaches the relief pressure Pfrl by the fuel-pressure forcible rise control, the fuel pressure Pf in the high pressure fuel system is acquired as determination fuel pressure Pf2, and when the determination fuel1 prescribed Pf2 is determined to be lower than failure determination fuel pressure KPf, it is determined that the relief valve 33 has no failure (normal). However, when the determination fuel pressure Pf2 is not lower than the failure determination fuel pressure KPf, it is determined that there is a failure of the relief valve 33 (for example, closed valve adhesion failure that the relief valve 33 is firmly adhered in a closed-valve state).