The overfill limiter is used on all vehicles and consists of a pressure valve and a vacuum valve. The pressure valve is designed to open when the fuel tank's internal pressure has increased over the preset pressure limit. The vacuum valve opens when a vacuum has been produced in the tank.
Remove the overfill limiter by loosening the clamps attaching the fuel line. Lightly breathe into the inlet and outlet. If the air passes through after slight resistance, then the valve is functioning properly.