1. Attachments are working again! Check out this thread for more details and to report any other bugs.

I Caught My Prius Farting!

Discussion in 'Prius c Main Forum' started by Oldwolf, Dec 8, 2012.

  1. Oldwolf

    Oldwolf Prius Enthusiast

    Joined:
    Feb 15, 2011
    816
    106
    0
    Location:
    NC
    Vehicle:
    2016 Prius v wagon
    Model:
    Four
    I went out to my garage a minute ago and heard my C making a weird farting noise. Like a small electric motor running. I finally pinpointed the sound to the bottom of the car back towards the fuel tank. At this point I thought my fuel pump was powered up because it sure did sound a little like that. I was saying to myself at that point that I am sure glad the car is still under warranty. So I went to get the SKS fob to start it up, hoping the sound would just go away. While sitting in the car prior to starting it, it occured to me that maybe I should remove the fuel cap first. While opening it a slight "whoosh" occurred blowing fumes in my face when removing the cap and the farting promptly went away. The tank is down to two segments level wise, it is cooling down this time of the day, but I did get back from a long drive a few hours ago, so I can't see how the fuel or vapors were expanding enough to release through a pressure valve. So if you car is farting, remove the gas cap first before panicking.
     
    #1 Oldwolf, Dec 8, 2012
  2. PriusCamper

    PriusCamper Senior Member

    Joined:
    Mar 3, 2012
    10,890
    4,416
    0
    Location:
    Pacific Northwest, USA
    Vehicle:
    2007 Prius
    Model:
    Two
    Read your owner's manual... It clearly explains what your car is doing in this situation...
     
    #2 PriusCamper, Dec 8, 2012
  3. vincent1449p

    vincent1449p Active Member

    Joined:
    May 24, 2004
    894
    331
    0
    Location:
    Singapore
    Vehicle:
    2012 Prius c
    Here is the quote from user manual, page 16:
    I think that is a bad idea. You are releasing gasoline vapors into the air! Hydrocarbons are a major cause of ground-level ozone pollution, or smog. In addition, gasoline vapors contain toxic pollutants such as benzene, a known carcinogen. That is why during refueling, gasoline stations must have vapor recovery system.

    http://www.mde.state.md.us/assets/document/factsheets/vapor_nozzle.pdf
    Oregon DEQ Air Quality: permits license vapor recovery stage

    Just ignore the sound, all cars are designed to reduce evap vapor by evap canister and will burn-off excess vapor at the same time during fuel injection.

    Vincent
     
    #3 vincent1449p, Dec 8, 2012
    PriusCamper likes this.
  4. etobia

    etobia Member

    Joined:
    Sep 8, 2008
    116
    11
    0
    Location:
    NEW YORK STATE
    Vehicle:
    2010 Prius
    Model:
    III
    Sorry Vincent but I'm lmaf. I'd much rather "relieve my gas" than ignore my body or my car! This is a few car toots. Who gives a shit....(oops there are carcinogens in my poop that will hurt you too, but I'll feel a whole lot better) :)
     
    #4 etobia, Dec 9, 2012
    CMJAnew likes this.
  5. Oldwolf

    Oldwolf Prius Enthusiast

    Joined:
    Feb 15, 2011
    816
    106
    0
    Location:
    NC
    Vehicle:
    2016 Prius v wagon
    Model:
    Four
    Thanks for the reference to the manual, this is the first time I have heard this sound. Then Gen2s have the fuel tank bladder which reduces the fumes released while fueling. Our C's have no such bladder so when you put a gallon of fuel in the tank out comes a gallon of gasoline saturated air. Also, many (maybe most) states do not have vapor recovery nozzles on dispensers as you mentioned, although many, if not most maybe, major cities do.
     
    #5 Oldwolf, Dec 9, 2012
  6. vincent1449p

    vincent1449p Active Member

    Joined:
    May 24, 2004
    894
    331
    0
    Location:
    Singapore
    Vehicle:
    2012 Prius c
    The Gen2 also has this Leak Detection Pump (2007 US User Manual Pg ix, 141 & 143) in addition to the fuel bladder. Here is a diagram from the Gen2 Repair Manual:

    Leak Detection Pump.jpg

    The sound you heard is coming from the Leak Detection Pump, not from the Fuel Pump. If the engine coolant temperature is not below 35ºC (95ºF) 5 hours (+- 15 min) after the power switch is turned OFF, the monitor check starts 2 hours later. If it is still not below 35ºC (95ºF) 7 hours after the power switch is turned OFF, the monitor check starts 2.5 hours later.

    The soundproofing of the C is worse than my Gen1, I believe also worse than the Gen2, which explains why you never heard in the Gen2.

    Vincent
     
    #6 vincent1449p, Dec 9, 2012
  7. Oldwolf

    Oldwolf Prius Enthusiast

    Joined:
    Feb 15, 2011
    816
    106
    0
    Location:
    NC
    Vehicle:
    2016 Prius v wagon
    Model:
    Four
    Very interesting about the leak test in the Gen2. However the C has no bladder and thus no interstitial space to test for leaks. What, then, is the system testing for leakage?
     
    #7 Oldwolf, Dec 10, 2012
  8. vincent1449p

    vincent1449p Active Member

    Joined:
    May 24, 2004
    894
    331
    0
    Location:
    Singapore
    Vehicle:
    2012 Prius c
    The bladder only reduces the interstitial space to minimize fuel vapors, can't stop fuel from evaporating. This evaporating vapor cause a pressure difference between the fuel tank and the atmosphere pressure. Depending which has the higher pressure, there will be leaks if the filler cap is not properly tightened, a hole in the lines, charcoal canister, or fuel tank.

    http://www.autoshop101.com/forms/h62.pdf

    Vincent
     
    #8 vincent1449p, Dec 10, 2012
  9. Ryephile

    Ryephile The Technophile

    Joined:
    Jul 10, 2012
    418
    151
    24
    Location:
    Metro Detroit
    Vehicle:
    2012 Prius c
    Model:
    Two
    Because it's federally mandated to ensure it's Evap system is properly functioning. Just leave it alone and there's no need to "burp" it by removing the fuel filler cap; it's not designed for human intervention.
     
    #9 Ryephile, Dec 11, 2012
  10. qbee42

    qbee42 My other car is a boat

    Joined:
    Mar 2, 2006
    18,058
    3,073
    7
    Location:
    Northern Michigan
    Vehicle:
    2006 Prius
    The fuel systems on all Prius, including the C, are sealed to keep vapors from escaping into the environment. There should be no path to the outside other than through the evaporative recovery cannister.

    Tom
     
    #10 qbee42, Dec 11, 2012
(You must log in or sign up to post here.)