Method of and apparatus for detecting fuel system leak

摘要

The existence of an unacceptable vapor leak can be determined by monitoring the pressure within a fuel system of an internal combustion engine. Once the engine is switched off, a period is timed to allow pressure variations due to movement of the fuel to subside to an acceptable level. The fuel system is closed and a first rate of pressure increase is determined by measuring a first time taken for the pressure to rise by a predetermined amount. A leak of a predetermined size is then introduced and a second rate of pressure increase is determined by measuring a second time taken for the pressure to rise by a predetermined amount. The first and second times are then compared to detect whether or not an unacceptable leak exists.