10 800GS Fuel Level Gone Wild

Discussion in 'Parallel Universe' started by BruceV, Aug 24, 2012.

  1. BruceV

    BruceV Been here awhile

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    I don't know if this has been discussed before - I looked and did not find it. Tonight while riding home - my fuel level went from full however many bars that is to half way - then a few miles later back to full - then back to half - and I only have riden about thirty miles since filling it up. The miles to empty seem accurate - any ideas what is going on?
    Thanks
    #1
  2. Indy Unlimited

    Indy Unlimited Long timer

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    Well known that the fuel level is only accurate when you got 1 gallon or less left in her. Then the mileage to empty and bars are very repeatable below a quarter of a tank.
    #2
  3. greenthumb

    greenthumb b00b

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    The way it works for me (and I believe most) is that the large top bar represents the top half of the tank and the multiple small bars the bottom half. If am around half a tank and I stop on steep incline or use the side stand without turning off the key, I get a similar behavior.

    I'm guessing that the fuel level indicated is an average of several readings taken over a minute or so to help account for sloshing and such and if the bike is at and odd angle for a length of time it will give a false reading.
    #3
  4. BruceV

    BruceV Been here awhile

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    The bike was basically full. It has never done this before - the bars have always stayed full until about 100 miles and then went to the half way amount of bars and went down accordingly. The miles to empty has always been very close and that was still working as far as I could tell.
    #4
  5. JRWooden

    JRWooden Long timer

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    Bruce:

    I've not heard of the problem before.... for what that's worth .......... (nut'n I think... )

    Did you fill on the sidestand to the bottom of the red dip tube?
    Has your bike taken any naps lately? :wink:

    I'd run down to near empty then fill to bottom of dip tube and see if it still behaves poorly ...
    If so I can't think of anything other than the sending unit that could cause the issue....
    #5
  6. BruceV

    BruceV Been here awhile

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    I did fill it on the side stand - but I always do that - I replaced the battery a couple of weeks ago - but has been working fine until last night. The bike was on a C-Tek battery tender for the past 10 days - I was traveling so it did sit - but again I do this all the time.
    #6
  7. vtbob

    vtbob wanderer

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    Yep, Because of the shape of the tank, BMW does not(can not?) guage the first half. Only guages the last half...and from my experiance pretty well.

    My bike is a 2010 and early on, the display guage seemed to work on an alogrithm base of ECU measure fuel consumption and estimate the level in the fist half. This algorithm was confused by people who rode the bike gently for a while then did a WOT for a while. the algorithm would show big changes in fuel in the top half of the tank...There were lots of blogs on this.

    At some point BMW got tired of the feed back and simplified ie turn off the estimation algorithm...it happen at the 18000 mile service for me.

    A portion of this algorithm is still at work with you miles remaining in the tank display.

    BAck to your problem...something is wrong with the sensor,wiring or the cal...see you dealer to get it fixed
    #7
  8. BruceV

    BruceV Been here awhile

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    Update:
    I may be back in business. I was checking connections and the connector on the top of the tank even though it seemed connected correctly - I unplugged and then plugged it back in and the fuel level - the bars are working correctly again. Maybe some dirt - corrosion - condensation or whatever was there but seems fine at the moment. Thanks for the help.
    #8
  9. TheCowboy

    TheCowboy back in the saddle again

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    Good to know Bruce, I am half way thru my Alaska trip and mine started doing the same thing. It is a 09 model and I have over 62,000 miles on her. I'll check the sensor connections. This is an Awesome Bike!

    TheCowboy
    #9
  10. Loutre

    Loutre Cosmopolitan Adv

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    when your next service is due ask for a remapping (they do it anyway I think) under warrenty (since it's a 10 model you still have a year left).

    otherwice I just see a disconnecting and reconnecting the sensor :eek:)
    #10
  11. EIGHTLUG

    EIGHTLUG Lost on purpose.

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    Quick question, kind of on topic. Once the fuel light illuminates and the MTE start counting up from zero, are you running on the reserve? Ive topped off, at that point (standard, on stand to bottom of tube) and only added 3.0 to 3.2 gallons. I believe the tank capacity is 4.7 U.S. Gal. So, reserve is 1.5 U.S. Gal? Am I on the right track?
    #11
  12. grndzr0

    grndzr0 its Ground Zero

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    Capacity is 4.2 gal. I believe they intended the gas light to come on at the typical 1 gal remaining reserve point.

    Ryan
    #12
  13. EIGHTLUG

    EIGHTLUG Lost on purpose.

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    Ahh yes, you're correct, 4.2 U.S. Gal. Makes sense now. Thanks.
    #13