gas fillup in ready mode

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by fintonissimo, Dec 26, 2010.

  1. fintonissimo

    fintonissimo Member

    Joined:
    Sep 17, 2009
    111
    8
    21
    Location:
    Chicagoland
    Vehicle:
    2008 Prius
    Model:
    N/A
    Ok, please don't beat me up for this...I've already repented!! I used to fill up with gas without shutting the car down, because I didn't see a need for it. :embarassed: I would disable the fan on the climate control every time to avoid having the ice come on as I refueled. I figured that because the ice wasn't coming on, I wasn't breaking the law. I've since changed my mind about this, after reading posts here on Prius Chat. I also recently noticed on the last few fillups that it seems like the gas capacity on the bladder has decreased significantly.

    I used to be able to refuel the car when it was down to a single flashing pip and put 10.5 gallons in with no problem, and without overfilling. I have always been careful not to overfill. However, it seems like now I can get only 8 gallons in at the most. The capacity has decreased with the colder weather, however I used to be able to get 10 gallons in on a consistent basis without overfilling even during the winter.

    Is this reduced bladder capacity a result of damage to the system, or is this normal? I have probably filled the car up about 100 times since I've owned it (odometer is around 50K now) while remaining in the ready mode.

    Is there anything I can do to expand the capacity of the bladder back to normal, or will I have to live with this? Although it's annoying, I'm not going to spend the money to replace the fuel tank unless it's truly necessary.

    Thoughts?
     
  2. edthefox5

    edthefox5 Senior Member

    Joined:
    Jul 25, 2007
    9,888
    4,647
    0
    Location:
    Clearwater, Florida
    Vehicle:
    2007 Prius
    Model:
    Two

    Its your ice cold stiff gas tank bladder. Its a common complaint in the winter.

    But I have found something that really helps gasing the car up.
    Its all pressure related. Everyone always complains about the constantly clicking off gas pump.

    I have found if you remove the gas cap and let the tank vent for a minute it really helps. Its becasue of the strict gas fume recovery system in the tank together with the flexible bladder it stays pressurized for quite a while.

    I get out at the gas station..lock the car...take the gas cap off....go inside and get a soda or whatever.. Come back in a minute or 2 and fill the tank on slowest click fill. First time it clicks off hang it up. It will usually be 7 to 8 gallons as I fill up on 2 pips always. Been doing this for more than 2 years and no overfill or gas belching drama or pump clicking off.

    Try it!
     
  3. Rokeby

    Rokeby Member

    Joined:
    Jan 21, 2008
    3,033
    708
    75
    Location:
    Ballamer, Merlin
    Vehicle:
    2008 Prius
    It is surprising that in the cold temps you see each year, you haven't
    experienced the typical Gen II fuel capacity reduction each winter.

    Since you aren't seeing any warning lights, things can't be greatly amiss.

    This probably isn't going to help get back that now missing fuel capacity,
    but there is a chance that the fore/aft, side/side inclination sensors that
    are used in calculating fuel in the tank/blader have gotten out of
    calibration. See page 3-2 here:
    http://www.autoshop101.com/forms/Hybrid13.pdf

    You might want to talk to your service writer/tech about a re-calibration
    next time you're in for service. There is reason to believe you can do a
    DIY readjustment. I can't find a procedure specifically for the '08. But
    here it for the '04, it is item 15 on page 5:

    http://greenhybrid.com/images/news/tsb_gasgauge.pdf
     
  4. fintonissimo

    fintonissimo Member

    Joined:
    Sep 17, 2009
    111
    8
    21
    Location:
    Chicagoland
    Vehicle:
    2008 Prius
    Model:
    N/A
    Thanks for the input. I always unscrew the cap and let it vent for a couple minutes before I fillup. I just filled up tonight with 1 unblinking pip left, and I put in 7.1 gallons in the tank before it shut off. I powered up the car and the fuel gauge was 1 pip shy of indicating a completely full tank. I drove around a bit and then went to a different gas station where I was able to put another .67 gallons into the tank. However, the fuel gauge still didn't indicate that the tank was full. I have never experienced this before, but since I've owned the car I have always filled it up in ready mode. Now that I'm turning it off when I fill it up, I wonder if that has affected the calibration.

    If I understand what your saying, a recalibration might make the gauge more accurate, but it isn't likely to change the volume of the bladder at all. Is there any way to do that?

    Thanks, Chuck
     
  5. Rokeby

    Rokeby Member

    Joined:
    Jan 21, 2008
    3,033
    708
    75
    Location:
    Ballamer, Merlin
    Vehicle:
    2008 Prius
    Chuck,

    In the 3 years that I've been here, I don't recall anything being brought
    up on changing the volume of the fuel bladder. Replacement of the
    tank/bladder is ~$700 + labor.

    The first cite I gave clearly says that fuel capacity is reduced in cold
    weather due stiffness of the bladder. The 2nd says that recalibration is
    the easier of the things for a tech to do for complaints of reduced fuel
    capacity. On the face of it, this may seem like a strange thing to do.

    My take on the recommendation is that when the inclination sensors
    are not calibrated, the readings from the fuel level sensor in the
    bladder/tank do not show the fuel at the bottom of the tank. The gauge
    may be showing and alarming a low fuel condition, but there is more
    fuel there. The only way to confirm this would be to run your car out of
    gas. I'm not hung up on mileage per tank, so I am not going to do this.

    It has been reported many times that when the "guess gauge" show low
    fuel, it takes at least 3 gallons before added fuel is registered on the
    gauge. It is assumed that this is true across the range of the tank.
    From this comes the general recommendation to fill as much as the
    bladder/tank will accept all at one time.

    All this is to say that when it comes to the peculiarities of the Gen II
    Fuel and Evap System, owners have to like it or lump it, tough beans.

    Since ~2006 the Camry hybrid has had the same PZEV air pollution
    rating as the Prius. But it doesn't have the bladder. So Toyota had
    some other way to control fuel tank emissions but didn't put it in the
    Prius. Why? Who knows.
     
    1 person likes this.
  6. fintonissimo

    fintonissimo Member

    Joined:
    Sep 17, 2009
    111
    8
    21
    Location:
    Chicagoland
    Vehicle:
    2008 Prius
    Model:
    N/A
    That's kind of what I thought...thanks for your explanations.

    Chuck
     
  7. tonyrenier

    tonyrenier I grew up, but it's still red!

    Joined:
    Jun 29, 2009
    362
    44
    13
    Location:
    Green Bay, WI
    Vehicle:
    2010 Prius
    Model:
    III
    My God! It's been like 2 Zillion Degrees below normal in the Midwest, be greatfull that you don't turn into an icicle while refueling. Remember spring is only 8 months away!!
     
Loading...