Patent ID: 6257050
Filing Date: 2001-07-10
Classification: F02M,G01L

Abstract:
An evaporative fuel leak diagnosing apparatus for an internal combustion engine, comprising:pressure sensor means for detecting a pressure within a fuel tank containing an evaporative fuel to be supplied to said internal combustion engine through an intake manifold;fuel tank seal-off means for isolating hermetically said fuel tank from said intake manifold and the atmosphere; andcomputer means for fetching directly a non-linear output signal that is representative of said pressure sensor as a function of a known set of previously registered data in an engine operating state where said fuel tank is hermetically isolated by said seal-off means, determining a pressure detection value indicative of a pressure level prevailing within said fuel tank on the basis of said non-linear output value obtained from said pressure sensor and data registered previously on the basis of the non-linear output values from said pressure sensor, and making a decision as to leakage of said evaporative fuel on the basis of a rate at which said pressure detection value increases.