Fuel Filler Cap: Description and Operation

PURPOSE
The fuel cap provides pressure and vacuum relief functions that allows the tank to vent.

CONSTRUCTION
The threaded screw-on design cap incorporates an integral pressure-vacuum relief valve.

OPERATION
Under normal operating conditions, the fill cap operates as a check valve preventing vapors from escaping the tank through the cap. Fuel system vacuum relief is provided after approximately -0.5 psi (-3.4 kPa) is reached inside the tank. Pressure relief is provided when pressure inside the tank builds up approximately 1.6-2.1 psi (11.1-14.4 kPa).