What is the reason for gas coming out when opening the fuel tank cap?
2 Answers
Vehicle opening the fuel tank cap has gas coming out because: gasoline in the fuel tank generates a certain amount of fuel vapor due to temperature changes and vehicle movement, and pressure is released when the fuel filler port is opened. The function of the fuel tank cap is to: record the vehicle model, standard tire pressure range, and the type of fuel for the vehicle. The components of the vehicle fuel tank are: fuel tank cap, partition, fuel gauge sensor, fuel inlet and return pipes, fuel filler port, and vent. The reasons why the fuel tank cap cannot be opened are: 1. The spring inside the fuel tank cap is stuck; 2. The fuel tank cap cable is damaged; 3. The fuel tank cap engagement area is aged; 4. The fuel tank cap motor is damaged.
I've been driving for over a decade and often encounter the hissing sound when opening the fuel tank cap, which is actually quite normal. Gasoline is highly volatile, especially during hot summer days when the vapor pressure inside the tank increases. When you stop after a long drive and open the cap, you hear that 'pfft' sound - that's the built-up gas being released. Also, filling the tank too full leaves insufficient space for vapor expansion. I once saw a young man at a gas station get gasoline splashed out immediately after unscrewing the cap, all because of thermal expansion in a completely filled tank. As long as the gas doesn't carry a strong gasoline smell, there's no need to panic. But if you detect a strong gasoline odor every time, you should have the charcoal canister and fuel tank sealing system checked.
