Diagnostic apparatus for evaporative fuel processing system

A diagnostic apparatus for an evaporative fuel processing system, comprising:

• a fuel tank configured to retain fuel to be fed to an engine equipped with a pressure charger;
• a canister configured to communicate with the fuel tank and capable of adsorbing evaporative fuel generated in the fuel tank;
• an upstream purge line configured to allow the canister and an intake system of the engine to communicate with each other at an upstream side of the pressure charger;
• an upstream purge valve disposed in the upstream purge line and configured to open and close the upstream purge line;
• a pressure detector configured to detect pressure in the upstream purge line;
• a valve controller configured to open the upstream purge valve when pressure-charging is performed by the pressure charger and to close the upstream purge valve during non-pressure-charging;
• a first timekeeper configured to accumulatively measure a time in which a diagnosis execution condition, including an amount of air taken into the engine and an open-close status of the upstream purge valve, is satisfied after the diagnosis execution condition is satisfied and a diagnosis for a purge flow in the upstream purge line is started;
• and
• a determiner configured to determine that the evaporative fuel processing system operates normally if the pressure in the upstream purge line detected by the pressure detector decreases by a predetermined pressure or more from the start of the diagnosis until an accumulative time measured by the first timekeeper reaches a predetermined time, and to determine that the evaporative fuel processing system operates abnormally if the pressure in the upstream purge line does not decrease by the predetermined pressure or more from the start of the diagnosis,
• wherein, every time the upstream purge valve is opened after the diagnosis execution condition is satisfied, the first timekeeper accumulatively measures the time in which the diagnosis execution condition is satisfied after a predetermined delay time elapses from when a command for opening the upstream purge valve is output.