What Causes Gas in the Fuel Tank?

[ElliotRose]

The presence of gas in the fuel tank is due to the difference in pressure between the inside and outside of the vehicle. The pressure inside the fuel tank is higher than the external pressure, causing the air inside the vehicle and some gasoline to flow under pressure, creating a jetting effect. When the airflow passes through a narrow space at high speed, the gas expelled by the car is actually a mixture of air and fuel vapor. More details about the fuel tank are as follows: 1. There is a carbon canister inside the car, located between the fuel tank and the engine, which balances the pressure inside and outside the vehicle. Therefore, if there is a jetting phenomenon when opening the fuel tank cap, it may indicate a problem with the carbon canister, which should be checked promptly. 2. The occurrence of gas jetting from the fuel tank is closely related to the season, especially in summer. As temperatures rise, the gasoline inside the tank expands and partially vaporizes due to heat, causing the internal pressure to exceed the external pressure. Hence, it is common to observe jetting when opening the fuel tank cap in summer. 3. After filling the fuel tank completely at a gas station, if the driver opens the fuel tank cap again, jetting may occur. This happens because the fuel tank is highly saturated with gasoline, leading to increased pressure.