How to Determine if the Fuel Tank Vent is Clogged?
2 Answers
If the vent is clogged, the pressure above the fuel tank will decrease, which is not conducive to the downward flow of gasoline to the carburetor. Hazards of a clogged fuel tank vent: Fuel tank collapse: With the continuous increase in the number of heavy-duty trucks, their safety performance has attracted more attention. During transportation, as diesel consumption lowers the fuel level, a certain vacuum forms inside the fuel tank. If the vent is clogged, the fuel tank may develop negative pressure due to the dropping fuel level, leading to inward deformation, commonly known as "fuel tank collapse." "Fuel tank collapse" not only causes deformation of the tank but may also prevent the fuel pump from extracting fuel, resulting in sudden engine stalling, insufficient power, and difficulty starting in a hot engine state. In severe cases, the tank may even rupture due to excessive deformation, leading to fuel leakage or even fire and explosion.
Having driven for so many years, I've encountered clogged fuel tank vents several times, and it's not hard to diagnose. Pay extra attention when refueling: if the fuel nozzle frequently shuts off automatically or the fueling speed is unusually slow, there's a high chance the vent is clogged. For instance, my old Jetta once kept stopping mid-refueling, and I could smell gasoline—turns out the vent was completely blocked by dust. Checking it yourself is easy too: after turning off the engine, unscrew the fuel cap and listen for airflow; there should normally be a hissing sound. If there’s no sound or the suction is too strong, it’s likely clogged. While driving, if the engine feels stifled or underpowered, poor venting could also be the cause. Don’t underestimate this—prolonged clogging can deform the tank, cause leaks, or even lead to engine failure. For regular maintenance, it’s best to clean the vent lines every six months to avoid roadside breakdowns and trouble.
