Check Valve Function Check

Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

CAUTION: Perform the inspection with the 12V battery connected.

Open the fuel filler lid. Here, the fuel tank solenoid is automatically released.
Open the fuel tank cap.
Disconnect the fuel vapor hose connector from the fuel vapor canister.

Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
Apply a positive pressure of 5 kPa (0.73 psi) and a negative pressure of - 5 kPa (-0.73 psi) to the fuel vapor hose and check for ventilation under each condition.
If ventilation does not occur, replace the fuel tank (integrated check valve) (Refer to Fuel Supply, Fuel Tank Removal and Installation REMOVAL AND INSTALLATION )