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Inaccurate fuel gauge

Discussion in 'New A3/S3 (8V Chassis)' started by AllanG, Aug 8, 2014.

  1. AllanG
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    AllanG Stronic

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    [Aug 8, 2014]
    My fwd 1.4 COD fuel tank holds approx 50 litres, however, when the fuel gauge is down to the 3/4 level and I refill, it takes approx 30 litres back to full.

    Personally, I find this amount of inaccuracy in the fuel gauge marking quite annoying, as I would expect when the level shows 1/2, I would have to refill approx 25 litres to refill to full.

    Has anyone else noticed this level of inaccuracy with their fuel gauge?

    Cheers, Allan
    #1
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  3. BigD289
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    BigD289 Member

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    [Aug 8, 2014]
    Not quite as bad but half full is less than 25 litres. It kind of seems to me like it is ignoring the red (reserve) led light from the measurement. But yes I have noticed the display does not match what is in the tank!
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  4. cuke2u
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    cuke2u Well-Known Member

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    [Aug 8, 2014]
    I think mine must be OK because I have just filled it up with 46l and it wasn't quite on the red part. Suggests yours Allen has a fault...
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  5. JohnnyM100
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    JohnnyM100 Active Member

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    [Aug 8, 2014]
    My gauge isn't bad but has the same (?software) quirks as previous analogue gauges:

    From full:
    Holds on to 8 bars for longer than you'd expect.

    1/2 tank is really about 5 bars

    Drop from 1 white bar to red is pretty quick.

    Long runs will give less accurate readings than shorter ones as the fuel is sloshing around in the tank and there is no frequent 'ignition off' to offset the smoothing.

    I often find that the gauge drops one bar between end of one journey and starting the car for the next one (and no, I don't have a leak in the tank).

    John.
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  6. cuke2u
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    cuke2u Well-Known Member

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    [Aug 8, 2014]
    Is the fuel gauge reading based upon fuel remaining and the driving conditions?
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  7. Leo-83
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    Leo-83 Member

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    [Aug 8, 2014]
    Your fuel tank measurements are based on 45l, not the 50l. For example, when you get down to the flashing red light and 0 mile range on the trip computer, you will only get 45l back into the 50l tank. There is a 1 gallon reserve that is unaccounted for.

    So base your calculations on 45l, not 50l. Half tank should therefore be 22.5l and 3/4 tank about 33l. Not that far off of what you are stating.
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  8. leosayer1
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    leosayer1 Member

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    [Aug 8, 2014]
    It takes 120-odd miles for the gauge on my SB to show any movement.

    I managed to put 51 litres in the tank the other day.

    Both are mildly annoying.

    I rarely look at the gauge, I find the DIS which tells me how many miles I've got left in the tank much more useful. As I recall, this is calculated by you the reaming fuel in the tank and average fuel consumption over the past 50km.
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  9. AllanG
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    AllanG Stronic

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    [Aug 8, 2014]
    Actually, when I said the 3/4 level, I meant that 1/4 of the fuel has been used, ie there is 3/4 of a tank left......sorry for the mis-understanding!
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  10. Leo-83
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    Leo-83 Member

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    [Aug 8, 2014]
    Oh okay, my misunderstanding. Filling a 50l tank with 30l when it's reading 3/4 full, yes, that is a little dodgy. Going on the proper maths, you should be filling it with about 10-15l max
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  11. CaesarBob
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    CaesarBob Member

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    [Aug 8, 2014]
    I can't really comment as mines not yet arrived ..... but presuming the fuel gauge won't take account of pipe from filler cap to tank either.
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  12. AllanG
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    AllanG Stronic

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    [Aug 8, 2014]
    That's what I would expect also, Leo, but this certainly isn't the case, and has been since I got the car back in April......perhaps a visit to my dealer is required?
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  13. monopole
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    monopole pro-monopole-ish-ism-istic

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    [Aug 8, 2014]
    looking through VCDS today on my car, you can re-calibrate the fuel gauge by all accounts!
    #12
  14. AllanG
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    AllanG Stronic

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    [Aug 8, 2014]
    Does this mean that an Audi dealer should be able to re-calibrate the fuel gauge?
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  15. monopole
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    monopole pro-monopole-ish-ism-istic

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    [Aug 8, 2014]
    can't see why not
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  16. driver_tim
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    driver_tim Active Member

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    [Aug 8, 2014]
    Well...a couple of weeks ago I refilled my car shortly after the fuel warning had come on and got 49 litres in...
    #15
  17. Leo-83
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    Leo-83 Member

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    [Aug 8, 2014]
    Do you have a 55l tank?

    The fuel light comes on when there's about 50m or so left in the tank, that's over a gallon (4.55l) Even if there wasn't a one gallon reserve (there is, all Audi's are the same, I'm on my 7th new Audi in the last 5yrs and all have been the same) then assuming a 50l tank you would have been running with a 50m fuel range (if the light had just come on) off of 1 litre in the tank, (less than a 1/4 of a gallon) That doesn't make sense, you would be doing about 250mpg if that were the case. I would go back to the garage and get them to re-calibrate their pumps.

    When I fill up my S3 with 0 range I only get around 50-51l back in. When I go 25m past 0 so really pushing it, I get 54l back in. S3 has 55l btw.
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  18. Leo-83
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    Leo-83 Member

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    [Aug 8, 2014]
    However, saying that. Filling technique also comes into play. I fill only to the first click, if I continue to fill the car until fuel is coming out of the cap, I can easily get 60l into a 55l tank as you fill the expansion tank and the cap to tank feed lines. I don't see the point in filling the car this way though, always to the first click for me.
    Last edited: Aug 8, 2014
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  19. Flibble
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    Flibble Member

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    [Aug 9, 2014]
    I always reckoned it being a 7l reserve. It'll be something in litres anyway; the Germans don't use gallons.
    #18
  20. monopole
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    monopole pro-monopole-ish-ism-istic

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    [Aug 9, 2014]
    My fuel light came on, DIS said 35 miles remain, put in 47L
    #19
  21. cuke2u
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    cuke2u Well-Known Member

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    [Aug 9, 2014]
    And it is definitely not a very good idea as it could cause a problem with the feed to the engine as the tank will not be able to breath..
    #20
  22. monopole
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    monopole pro-monopole-ish-ism-istic

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    [Aug 9, 2014]
    I'm assuming it's this

    tank.jpg
    tank2.jpg
    #21

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