A fuel tank loses pressure when components that maintain its sealed, balanced pressure system fail—this issue disrupts fuel delivery and can harm engine performance, often stemming from specific faults in key parts.
Fuel tanks rely on a vent pipe or pressure-relief valve to regulate pressure: as fuel is used, fresh air enters through the vent to avoid vacuum buildup, and excess vapor escapes to prevent overpressure.
- If the vent pipe becomes blocked by dirt, debris, or corrosion, air cannot enter the tank
- This blockage leads to a vacuum that lowers internal pressure
- A stuck or worn pressure-relief valve may fail to seal properly
- This allows pressure to leak out even when the tank needs to retain it
The fuel tank cap uses a rubber seal to create an airtight closure; over time, this seal cracks, hardens, or wears down, breaking the tank's seal and letting pressure escape.
- Seals around fuel lines, connectors, or the fuel pump can also degrade
- Loose connections or worn gaskets create small gaps where pressure seeps out
- These leaks typically occur during vehicle operation
Cracks, holes, or corrosion on the tank's body provide direct paths for pressure to escape.
- Even small cracks, invisible to the naked eye, can let air leak out gradually
- This gradual leakage disrupts the tank's pressure balance
- Corrosion weakens the tank structure and creates potential leak points
The fuel pump's internal seals keep gasoline contained and maintain system pressure; if these seals wear or break, pressure leaks around the pump.
- Worn or broken seals reduce overall tank pressure
- This often pairs with engine performance issues like hesitation or stalling
- The pump cannot deliver fuel at the required pressure when seals fail