Patent ID: 7284530

Claim:
A leak detector for a fuel vapor purge system introducing a fuel vapor in a fuel tank into an intake pipe of an internal combustion engine, the leak detector comprising: a pressure-introducing-detecting apparatus including a pressure introducing unit introducing a pressure into the fuel vapor purge system including the fuel tank; a reference-pressure-detecting portion provided with a reference aperture having a predetermined inner diameter; and a switching unit switching between a passage for introducing pressure into the reference-pressure-detecting portion and a passage for introducing pressure into the fuel vapor purge system; and a leak determination unit detecting a reference pressure information representing a reference pressure adjusted by the reference aperture or correlated information of the reference pressure, the leak determination unit detecting a system pressure information representing a system pressure in the fuel vapor purge system or correlated information of the system pressure, the leak determination unit determining whether a leak exists by comparing the reference pressure information with the system pressure information, wherein the leak determination unit adjusts a control value of the pressure introducing unit using the reference pressure information as a target condition to set a first control value when the reference pressure information satisfies the target condition, and thereafter drives the pressure introducing unit at the thus set first control value during a leak detecting operation.