Vacuum in Fuel Tank - 98 ford windstar 3.8 liter

[jayjp200]

Hello,
Recently few times I have noticed that there is Vacuum in Fuel Tank on my 98 Ford Windstar 3.8 liter.
When ever after driving, I open the fuel cap I hear a hissing sound as if air getting sucked in for 3 seconds.
Is this normal - what can be wrong here?

Please share your thoughts.
Thanks.
Jay

[tempfixit]

Originally Posted by jayjp200

Hello,
Recently few times I have noticed that there is Vacuum in Fuel Tank on my 98 Ford Windstar 3.8 liter.
When ever after driving, I open the fuel cap I hear a hissing sound as if air getting sucked in for 3 seconds.
Is this normal - what can be wrong here?

Please share your thoughts.
Thanks.
Jay

Is your check engine light on?? ANy codes?? Faulty Gas Cap possibly.

[Windstartled]

I would suspect fuel tank pressure sensor fault. The PCM uses this sensor to vent vapors through the purge valves of the evaporative emissions system.

[olopezm]

I don't think there's anything wrong with it, that's the way the EVAP system was designed and all of my 3 cars do the same if you remove the gas cap right after turning it off.

Oscar.

[Windstartled]

Originally Posted by olopezm

I don't think there's anything wrong with it, that's the way the EVAP system was designed and all of my 3 cars do the same if you remove the gas cap right after turning it off.

The occasional presence of a pressure buildup in the fuel tank at refill time is not abnormal but if it happens consistently it may be a symptom that the PCM is failing to trigger automatic vent due to faulty sensor. One way to confirm this without testing the sensor itself would be inaccurate readings from the fuel gauge but it's not that easy to tell if the gauge is wrong when the discrepancies are minor. Personally I would probe the sensor just to make sure.