Fuel Tank

When fuel tank pressure exceeds a preset value, 2-way valve opens, allowing excess vapors to vent into canister. If excessive vacuum forms in fuel tank, 2-way valve opens to allow outside air into fuel tank through canister. A vacuum/pressure fuel filler cap with higher release points than the 2-way valve acts as a safety valve if evaporation system fails.

Fig 1: Fuel Evaporation System (Accord EFI)

Courtesy of HONDA MOTOR CO., INC.

Fig 2: Fuel Evaporation System (Civic EFI)

Courtesy of HONDA MOTOR CO., INC.