Vented Vs Non Vented Fuel Cap

A non vented cap is just that no venting at all and will not let air in or out so unless you have an eec tank or other vent setup elsewhere you ll have some issues.

Vented vs non vented fuel cap.

Gas caps have not been vented since the introduction of evaporative emission controls smog control on cars many years ago. The vented gas cap has a one way release valve that is pressure activated. Gasoline systems have been running non vented caps for quite a while due to the emissions requirements. If that tube is not present then you need a vented gas cap.

The non emissions caps freely vent the tank to the atmosphere which can waste gas through evaporation. Both styles of caps provide vacuum relief. Emissions gas caps have a built in pressure relief valve that will only vent to the atmosphere if the pressure gets too high. Gas fireplaces come in two configurations.

Ventless logs do not put off these emissions so no chimney or flue is needed and the heat is more likely to stay in your space. Using a non vented cap on a car from the 1960 s that required a vented cap can cause the car to run for a while until the fuel system draws a vacuum in the gas tank. The vented gas cap is designed to vent small amounts of air into the car gas tank line. If your tank has a vent then you will need a non vented cap.

Vented caps only vent one way into the tank to allow air in as the fuel is used to prevent a vacuum from occurring. All modern vehicles use a non vented cap. When the pressure reaches a certain point defined by so many pounds per square inch the valve opens by a very small amount relieving some of the pressure.