A method and apparatus for measuring leakage of a vehicle fuel system includes providing an apparatus having a gas source, a pressure meter and a reference orifice and connecting the apparatus to the fuel system. The fuel system is pressurized with the source. A first set of pressure measurements is obtained using the pressure meter with gas escaping the fuel system through leakage of the fuel system. A second set of pressure measurements is obtained with gas escaping the fuel system through leakage of the fuel system and through the reference orifice. An effect of fuel vapor pressure created by fuel in the vehicle fuel system may be measured. A leakage parameter of the fuel system may be calculated from the first and second sets of pressure measurements including compensating for the effect of fuel vapor pressure.
CROSS REFERENCE TO RELATED APPLICATIONS
This application claims priority from U.S. provisional patent application Ser. No. 60/548,078, filed on Feb. 26, 2004, the disclosure of which is hereby incorporated herein by reference in its entirety.
