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Petrol Gauge shows 1/4 tank when empty..help

Discussion in 'A3/S3 Forum (8L Chassis)' started by coyle, Dec 31, 2010.

  1. coyle
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    coyle From Show... to GO

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  2. colicabcadam
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    colicabcadam Guest

    my guess is that the sensor operates on a float, maybe it's just getting stuck? i doubt it's the pump, i can not see how the fuel pump would know how much petrol is in the tank.... all it does it pressure the fuel its being fed so the injectors can squirt it into the cylinder
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  3. NHN
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    NHN Modmetractor Site Sponsor

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    These do happen on the MK1 & TT's, mine did this few times on my S3 & fixed itself but if persists then I'd look at the gauge sender in the tank/pump as 1st port of call as suggested already.
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  4. Andrew@A.L.D
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    Andrew@A.L.D Cylinder Head Master

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    I had this problem on another car and i filled the tank to the top and it seamed to fix it?
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  5. NHN
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    NHN Modmetractor Site Sponsor

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    Yeap also heard that aswell, some have had to do 2-3 fills, but fixed itself.
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  6. coyle
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    coyle From Show... to GO

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    mines been doing it for 2months (since i got the car) and its had about 8 fill ups :(
    so what is it i should be looking for in the sender? is it a replacable part? i pressumed its all one unit hence needing the whole pump etc
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  7. rossbrownlee
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    rossbrownlee Ross_S4

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    coyle is yours a quattro mate?
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  8. coyle
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    coyle From Show... to GO

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    it is buddy
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  9. rossbrownlee
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    rossbrownlee Ross_S4

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    probably your suction jet pump, here is copy from elsa:

    The electric fuel pump sends a pressurised stream of fuel into the suction-jet pump (entrainment pump) in the left chamber of the tank.
    The suction-jet pump delivers the fuel from there into the right chamber, and from the right chamber it is drawn into the fuel delivery unit.
    Faults caused by defective suction-jet pump
    WARNING
    If the suction-jet pump is defective, the engine can stop due to fuel starvation when the tank is still 1/4 full.

    If suction-jet pump -2- is not working, up to 15 litres of fuel -3- (up to 1/4 of tank capacity) may remain in the left chamber of the tank, where it cannot be drawn into the fuel delivery unit.
    If the engine stops due to fuel starvation with the tank up to about 1/4 full, proceed as follows:
    – Check fuel pump → Chapter.
    If fuel pump is OK, but no fuel is delivered:
    – Put another 5 litres (approx.) of fuel into tank.
    – Start engine.
    – If engine does start now, renew suction-jet pump → Chapter.
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  10. coyle
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    coyle From Show... to GO

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    great advice mate, thanks,
    but i dont see how that 100% helps

    because surely if the car cuts out from fuel starvation, (which it has done) and i put 5litres in it, then it starts, that doesnt rule out the sender?

    when it shows 1/4 tank (which is when it cuts out) I can put in about £67, but if there was still 15 litres in the tank that would be about an £85 fill up from empty? does that sound right?

    I currently get around 300miles at about 26mpg from my £67ish. thats from a full tank down to a 1/4 tank

    is there any way i can take it down to 1/4 tank which is when it cuts out then check the left chamber to see if it has any fuel in there?
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  11. rossbrownlee
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    rossbrownlee Ross_S4

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    I am not 100% sure how the level measurement systems work together with the two senders G and G169.
    You could measure the resistance on the level sender when it cuts out again. again from elsa:
    Fuel gauge sender -G- installed:
    l
    Sender at lower stop: approx. 59 ohms
    l
    Sender at upper stop: approx. 282 ohms


    This is the sender under the rear seat drivers side and measuring the middle two connections.
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  12. coyle
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    coyle From Show... to GO

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    that seems abit technical for me haha.. i was hoping i would be able to just lift out the pump and see 15 litres of fuel staring at me and hey presto i know the problem haha.

    although.. if that it the problem, i dont know how i'd replace it or where to get the replacement
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  13. david7m
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    david7m Member

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    Mine has done this since I had a new fuel pump, it ran out the other week when it said I had 80 miles left :(

    Dave
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  14. chris99
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    chris99 s3 driver

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    well if that's a quattro the one from ebay link doesn't fit your car

    as far as i understood after i lost one day trying do make mine work, it's shown an average of both, but not an arithmetic average.
    one is a normal level sensor and the other (from the left side of the tank) is for accuracy. i gave up with mine, just ordered another one.. waiting to get it :)
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  15. BL33SU
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    BL33SU New Member

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    A bottle of Fuel injector cleaner with your petrol!

    it fixed mine straight away.. i think the sensor is stuck or news cleaning inside the tank
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  16. chris99
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    chris99 s3 driver

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    got lucky as it was only the contact surface a little dirty.. i tried that too but no change
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  17. coyle
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    coyle From Show... to GO

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    So is there any way to tell for sure if its the second pump or the sender?
    I dont want to try and fix something thats not broken (and brake it while doing so :p )
    #17
  18. chris99
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    chris99 s3 driver

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    probably you're talking about the suction-jet pump (just an entrainment pump) that is less posible to break down, maybe just some garbage there and it's stuck (it's mechanical) or the hose between the chambers stuffy

    you got to remove carrefully the fuel senders from both chambers and check inside the tank:
    1. if you see empty chamber on the right side of the car and some gas in the left, it's something wrong with the hose or entrainment pump. other possible scenario is the fuel pump dying and not enough pressure on the return hose to move the gas in left half of the tank, but this could be check in high acceleration where the car should feel missing some fuel
    2. if both are empty, most probably you'll need another sender or could try repair if possible
    #18

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