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Thread: Fuel Temp Sensor

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  1. Re: Fuel Temp Sensor 
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    I assume the 2.5V he got at the sensor connector was measured with the sensor disconnected. If that's the case we already know the problem can't be with the sensor itself and it can't be anything to do with the temperature of the fuel...since the sensor wasn't connected.
     
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  2. Re: Fuel Temp Sensor 
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    My thoughts re fuel temp, was that ecu being told from other sensors that its up to temp but fuel temp saying not--might be causing a conflict in ecu, so EML on ??? just a thought !!
     
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  3. Re: Fuel Temp Sensor 
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    have you got vagcom/VCDS ?? If you do, what does the fuel temp read in engine controller, group 7?
    With the car dead cold, how close are all three temperature readings?

    I was messing around with this today actually and found something very interesting.

    I pulled all the old wiring out right back to the connector under the cowl. Hooked my test leads up to the two wires and run them to the sensor connector pig tail. Check my VCDS and hey I'm getting a reading other than 39.6!

    So I solder on new wires, carefully routing them down to the sensor making everything nice and neat. Connect everything up, go to check the temp readings and it's back to 39.6 again!

    Now here is the interesting part. If I connect a test lead to the black wire and ground it out presto the sensor reads correctly. Unhook it and the engine hiccups ever so slightly and the reading goes back to 39.6.

    I take it that this is a bad ground?

    Since the ground wire goes back to the connector under the cowl, what grounds the other pins under there? Coolant and intake air temp sensor wires go back to that connector, wouldn't they all lead to a single common ground at some point? Those sensors are working fine.

     
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  4. Re: Fuel Temp Sensor 
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    Quote Originally Posted by Vagnuts View Post
    My thoughts re fuel temp, was that ecu being told from other sensors that its up to temp but fuel temp saying not--might be causing a conflict in ecu, so EML on ??? just a thought !!
    Your probably right. The ECU is logging the fuel temp code because the sensor input is implausible when compared to other engine temperatures.

    But we need to establish why the temperature signal getting back to the ECU is incorrect. In the OP's case we know it can't be the sensor itself or the actual temperature of the fuel that's wrong because the voltage on the sensor connector was incorrect with the sensor out of the circuit. When the circuit is open (therefore, no current flow) there should be 5V at the sensor connector but the OP only measured 2.5V.

    Quote Originally Posted by Vagnuts
    I take it that this is a bad ground?
    It certainly sounds like it.

    Quote Originally Posted by Vagnuts
    Since the ground wire goes back to the connector under the cowl, what grounds the other pins under there? Coolant and intake air temp sensor wires go back to that connector, wouldn't they all lead to a single common ground at some point? Those sensors are working fine.
    Engine sensors generally share a common ground that's inside the ECU. Each sensor ground is usually on a separate ECU terminal so it's possible for there to be a poor connection on the ground to one sensor without it effecting any of the others.
     
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  5. Re: Fuel Temp Sensor 
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    So is the black wire an earth and can be connected to a bolt or screw to earth it? Therefore the sensor would work ?
    VW POLO 2002 1.2 12v , Audi A6 2006 2.0 TDi SE , Skoda Fabia 1.4 TDi

    All 3 cars in the current fleet
     
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  6. Re: Fuel Temp Sensor 
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    "I think that would/could be worth a try" , though maybe a thought to just take ecu out, and have "visual check of pins and harness--sings of green water/moisture damage", just a thought !!! an while ecu out---clean up the earthing point for it b4 putting back on !!!
     
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  7. Re: Fuel Temp Sensor 
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    I wonder if the guy who actually started the thread has got to the bottom of his problem yet?
    Are you still with us @Bobs2293
     
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  8. Re: Fuel Temp Sensor 
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    Hmmm, was thinking same as above post---it would be good to have feed back/confirmation of any if any improvements !!!
     
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  9. Re: Fuel Temp Sensor 
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    Re: Fuel sensor
    Im wondering if they got it sorted too
     
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  10. Re: Fuel Temp Sensor 
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    Was wondering if this thread is dead as I have similar problem on 2004 Tdi 1.9 where over temp alarm has come on.
    Also i am really confused re this issue of the fuel temperature return valve as i can't find any reliable info on the subject.
    Some seem to think it is in top of the fuel filter tank, but in this document pages 8 and 9 there is no such fuel temperature return valve as all fuel returns to the tank is cooled.
    http://pics.tdiclub.com/data/517/114..._PumpeDuse.pdf

    Any ideas please.
     
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