Why does it say the fuel tank pressure is high when refueling?
2 Answers
When refueling, the fuel tank pressure is high because the temperature of the gasoline increases while driving, causing slight evaporation. This results in some gasoline vapor in the fuel tank, which increases the pressure. It is recommended to buy a bottle of fuel additive to help reduce the pressure. The fuel tank maintains a certain level of pressure. When the fuel cap is opened, the pressure is released, which can produce a sound. Normally, the pressure is regulated by the one-way valve in the fuel cap to keep the fuel tank pressure stable. Except during refueling when the fuel tank is in a semi-sealed state, it remains fully sealed at other times. However, as the vehicle ages and is used over time, sediment and impurities in the fuel tank will accumulate and inevitably enter the engine through the fuel supply system, potentially causing damage to the car over time.
I noticed the high fuel tank pressure warning appeared during my last refueling, which usually indicates an issue with the evaporative emission control system. Gasoline in the tank evaporates and produces vapor, which normally releases pressure through the charcoal canister and vent lines. However, if the canister becomes saturated or clogged, vapor accumulates, causing high pressure. My car has encountered this several times—each time, the pump nozzle would automatically shut off or show abnormal pressure warnings. This is mainly due to inadequate maintenance of the charcoal canister, possibly caused by dust or debris blocking the vents, or frequently refueling with the engine running, leading to excessive vapor buildup. The solution is to visit a professional shop to check if the canister needs replacement or to clean the ventilation system. Regular maintenance can prevent this issue, as high pressure not only interrupts refueling but also increases the risk of combustion. I’ve noticed it happens more often in hot weather, so I make it a habit to check the vehicle’s ventilation before refueling in summer.
