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Pressure build-up in the gas tank

Discussion in 'Chevy Trucks' started by scottyknows50, Nov 18, 2010.

  1. scottyknows50

    scottyknows50 Member
    Messages: 93

    I have a 2000 2500 Silverado. There has always been a "woosh" of air when I unscrew the gas cap. Anyone know what the cause of this is? My SES light came on today, I put some gas in, and soon after the SES light went off. Is this pressure causing a sensor to trigger? Thanks.
     
  2. RepoMan207

    RepoMan207 PlowSite Fanatic
    from Maine
    Messages: 5,038

    That typically happens when you run your tank low on gas. The vapors build up. It also happens when one drives very erratically with low fuel levels. Typically, I think it has to be in warm weather as well.
     
  3. Holland

    Holland Senior Member
    Messages: 605

    Is the air "whoosh"-ing in or out of the tank?
     
  4. scottyknows50

    scottyknows50 Member
    Messages: 93

    well, it's been about 35-50 degrees here this past week and i'm not sure if the air is rushing in or out, i will have to feel with my hand next time i drive it. SES light came on AGAIN today after about a 10 minute drive. it seems to always do this- if i have an eighth of a tank or over half.
     
  5. RepoMan207

    RepoMan207 PlowSite Fanatic
    from Maine
    Messages: 5,038

    Maybe your vent side is plugged up?
     
  6. Flipper

    Flipper PlowSite.com Addict
    from CT
    Messages: 1,180

    Try replacing the gas cap.
     
  7. 496 BB

    496 BB Senior Member
    Messages: 789

    Check the code at Auto Zone.
     
  8. Philbilly2

    Philbilly2 2000 Club Member
    Messages: 2,643

    Somone told me once that it is because your vent is plugged.
     
  9. flykelley

    flykelley 2000 Club Member
    Messages: 2,124

    Vents being pluged is a common problem, are you having a hard time putting gas in the tank? When mine vent was plugged I had a hard time putting $10.00 worth of gas in the tank. Chevy makes a kit to relocate the vent tube.

    Regards Mike
     
  10. scottyknows50

    scottyknows50 Member
    Messages: 93

    where is the vent and how can i "unplug" it?
     
  11. Holland

    Holland Senior Member
    Messages: 605

    Get your truck hooked to a scan tool before you start unhooking stuff. Even if you can just get the code number. I have alldata i can look it up for you.
     
  12. scottyknows50

    scottyknows50 Member
    Messages: 93

    ok, i will see if advanced auto parts has a code reader. i don't have an autozone nearby.
     
  13. scottyknows50

    scottyknows50 Member
    Messages: 93

    I scanned the truck today and the codes said O2 sensors (both?) and Throttle Position Sensor. The code reader also said after every one "circuit malfunction"- anyone know what this means?? The guy at the auto parts store didn't. The truck is acting weirder as time goes on. My tranny has started to shift quite abruptly. I'm not sure if it just happens to be happening now, or if somehow something isn't getting enough power- I guess I'm lost. Thanks for any help.
     
  14. Holland

    Holland Senior Member
    Messages: 605

    Do you have the actual codes? Would make things alot easier.
     
  15. stacks04

    stacks04 Senior Member
    from ct
    Messages: 119

    Sometimes when a ses light is on because a sensor is not providing the ecm with a reading or giving an improper reading the ecm will default to known values for things like shifts and fuel distribution. This could cause the vehicle to react differently than if it had the proper readings. It is a failsafe that the ecm has so in the event of a single electrical failure you will be able to still drive the vehicle, preferably to a repair shop. O2 codes will hurt fuel economy but not usually anything else. Probably a o2 heater code.
     
  16. Reliable Snow and Ice

    Reliable Snow and Ice Senior Member
    Messages: 981

    could also be cataliac converter being plugged up