GM Service Manual Online
For 1990-2009 cars only

Fuel Tank Vent Valve Check

The fuel tank vent valve is located in the rear of the vehicle near the fuel tank. The fuel tank vent valve is a pressure/vacuum relief valve. If the valve is not functioning properly it could cause excessive pressure or vacuum to build up in the fuel tank. The result may be possible fuel discharge when removing the fuel filler cap or possible damage to the fuel tank or the fuel sender.

  1. Loosen the fuel filler cap in order to relieve the tank pressure.
  2. Remove the tank vent valve from the vehicle.
  3. Wrap the vent valve in a shop towel and shake out any remaining fuel.
  4. Connect the vent valve to a radiator pressure check device using the appropriate adapters.
  5. Slowly apply pressure to the vent valve. The valve should open at approximately 1 psi. If not, replace the vent valve.
  6. Disconnect the vent valve from the pressure tester.
  7. Connect the vent valve to a hand operated vacuum pump using the appropriate adapters.
  8. Slowly apply vacuum to the vent valve. The valve should open at approximately 1-2" Hg. If not, replace the vent valve.