Smoke from diesel tank when opening???





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  1. #1
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    Default Smoke from diesel tank when opening???

    Last nignt I openned the filler cap on my 2006 ML320 Diesel and a lot of white smoke came out as the pressure released ,it kept coming out as long as I put fuel in ,it was just about 1/4 tank when I started filling ,car was driven and the ambient temp. was a little bit lower than normal +-14C ,did anyone else experience this before.

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    Default Re: Smoke from diesel tank when opening???

    Might be that the diesel from the underground storage was very cold.
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    Default Re: Smoke from diesel tank when opening???

    The smoke come out before I started to put fuel in.

  4. #4
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    Default Re: Smoke from diesel tank when opening???

    Next time smell if it's smoke or steam.
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    Default Re: Smoke from diesel tank when opening???

    Well if it is either one ,where is it coming from and what can cause this ,I think it might be to do with the temp. and pressure difference ,what I want to know is if someone else seen this before or experienced it before on a diesel vehicle.

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    Default Re: Smoke from diesel tank when opening???

    As you say the vehicle had just been driven, it might be that the fuel return had put a lot of hot fuel back into the tank which had cooler fuel in it. How hard had you driven the vehicle before opening the cap? The harder you drive a diesel, the more unused fuel is returned to the tank, if I am not mistaken.

    No, I have never experienced this before, so I am just theorising. Might also have something to do with relative humidity, ambient temp etc together with excess moisture in the tank, which steamed when hot fuel was added to it. Diesel has moisture in it already, hence the need for a water trap in your fuel system.

    Has the vehicle ever stood for extended periods with less than a full tank? If it has, the remaining fuel sweats and coats the tank with water vapour. In the long term, you will have layer of algae growing in your tank underneath the remaining diesel.
    Last edited by Naes-Landy; 2016/06/01 at 11:24 AM.
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    Default

    Check your fuel pipes aren't running next to a hot surface maybe. Are your tank.breathers not blocked.
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  8. #8
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    Default Re: Smoke from diesel tank when opening???

    Quote Originally Posted by WTaute View Post
    Well if it is either one ,where is it coming from and what can cause this ,I think it might be to do with the temp. and pressure difference ,what I want to know is if someone else seen this before or experienced it before on a diesel vehicle.
    I've never heard of or seen this.
    common rail diesels return highly pressurised fuel back to the tank and this can get very very hot.

    If you have very little fuel in the tank, all the diesel will reach a high temp very quickly. Residual water in the tank will vaporise and form steam.

    THAT BEING SAID: you shouldn't have that much water in your fuel tank...........
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    Default Re: Smoke from diesel tank when opening???

    Hot breath on a cold day.

    The fuel in your tank is rather hot after a drive.

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    Default Re: Smoke from diesel tank when opening???

    Fuel is hot after drive, the return pipe took back some warm sous
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    Default Re: Smoke from diesel tank when opening???

    Quote Originally Posted by jelo View Post
    I've never heard of or seen this.
    common rail diesels return highly pressurised fuel back to the tank and this can get very very hot.

    If you have very little fuel in the tank, all the diesel will reach a high temp very quickly. Residual water in the tank will vaporise and form steam.

    THAT BEING SAID: you shouldn't have that much water in your fuel tank...........
    diesel floats on top of water so any moisture will be picked up first by the pickup and either stop in the filter or go through to the injectors......

    See why filters and water traps play such an important role. The bad stuff gets picked up first.

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    Default Re: Smoke from diesel tank when opening???

    Remember that in any CRD engine the diesel gets pumped by the high pressure pump in to the common rail at between 1000bar-2000bar (15000Psi-2500Psi).

    That is one mo.r of a pressure and diesel heats up to something like 70degC (actually much warmer but gets cooled by the diesel cooler again before it reaches the tank, IIRC) in this process. Only a small amount of that diesel gets used and the rest gets send back to the tank via the diesel return pipe.

    When outside temps are so low (+_14degC) it will look like vapor/smoke.
    Last edited by Regard; 2016/06/01 at 03:37 PM.

  13. #13
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    Default Re: Smoke from diesel tank when opening???

    Yip ...I think it is the Temp. and Pressure Difference.

    Thanks.

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