Leak test, pressure
WARNING: This page is about a different car, the 2004 Volvo S40, 2003 Volvo S40, 2002 Volvo S40, 2001 Volvo S40, and 2000 Volvo S40. However, it is still accessible from the selected car via links, so may be relevant.
Courtesy of VOLVO CARS OF NORTH AMERICA.
Set the selector to position PRESSURE.
Slowly pump in the air to plus (+) 3 kPa. Wait until the pressure has stabilized. Pressure reductions of 1 kPa per 30 seconds are permitted.
Replace any fuel filler cap that fails this test.