Pressure difference detector, a method for judging an abnormality of the detector, and a fuel vapor emission preventing employing the detector

摘要

A pressure difference detector for detecting a pressure difference between atmospheric pressure and a fuel system vapor pressure to be measured, includes a pressure dampening member 17a for dampening the flow of atmospheric air between an introducing inlet 11a and a reference pressure chamber 12 to limit the air flow rate to a value smaller than a leakage flow rate between the chamber and a fuel system vapor pressure introducing inlet 11b due to a leaking 0 ring seal. This prevents an erroneous judgment that the fuel system is leaking.