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how do I depressurise the fuel filter so I can change the fuel filter?

Discussion in 'Engine, Drivetrain, Fuel and Exhaust' started by w210chap, Jan 24, 2010.

  1. w210chap

    w210chap Member

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    This is my first post. I've found this site really useful so far.

    I'm trying to replace the fuel filter on my W210 '02 Reg Diesel Automatic. I've read that to depressurise the fuel filter I need to run the engine then while its on remove the fuse to the fuel pump - this should cut out the engine once there's no more fuel in the filter. I've done this, but the engine just keeps running - even after several minutes there's no sign of the engine cutting out. (The fuse is the 25Amp one in slot 6 in the fuse box under the rear seat as per the MB list).

    Am I going about this correctly, or am I missing something?

    Also, once I get past this holdup (help please:?:) and have replaced the filter, I believe this model's fuel system is self-bleeding. I'll fill the fuel filter canister with fuel before refitting the fuel lines, but is there anything else I need to do to prevent air getting into the fuel system? I've read other posts, eg links to the tech diagrams on detali.ru, and can't find any sight of a primer pump in the engine.

    Any help/info will be appreciated.
     
  2. Cole@MBS

    Cole@MBS Forum Supporter Authorised Forum Supporter

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    Dont worry about all that, just remember to top the new filter up with fuel before refitting it,

    Welcome to the forums!!
     
  3. OP
    w210chap

    w210chap Member

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    Do you mean that I don't need to depressurise the fuel system first? With the engine off should I just disconnect the fuel lines going into the filter, then replace the filter etc?

    Thanks for your reply.
     
  4. Cole@MBS

    Cole@MBS Forum Supporter Authorised Forum Supporter

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    Thats the way i have always done them, if your worried then put a bit of rag over the joint as you take it apart!!
     
  5. Alex Crow

    Alex Crow Senior Member

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    w210chap, you are thinking about the filters on petrol cars! just do as sam unit says, and top up the new filter before you fit it. btw you may have some trouble starting the car at first, filling the filter will help.
     
  6. OP
    w210chap

    w210chap Member

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    Thanks for both replies. I didn't realise the fuel pressure was not such an issue in diesels. I'll give this a go next weekend, with a rag to catch any spillage.

    Thanks again.
     
  7. Alex Crow

    Alex Crow Senior Member

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    there will be no pressure chap, none at all.
     
  8. OP
    w210chap

    w210chap Member

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    Everything went according to plan (almost). Disconnected the fuel lines - the only problem there was I snapped the little black plastic ring that hooks the top inlet line to the fuel filter case (superglued that back together!). Replaced the fuel filter (with MB part), couldn't get the old fuel line clips back on so used screw-on ones from Halfords. Filled the fuel filter with diesel. I also filled the fuel lines with diesel (as much as I could anyway) before re-fitting them. Expected trouble with re-starting the engine, but none at all - the engine started straight away. Tested for leaks with the engine running - none apparent.
    All in all a relatively straightforward job. Next time I'll use even more rags to catch the fuel when disconnecting the fuel lines, as I spent quite a while wiping up the little diesel that had found its way to the bottom of the engine compartment.

    Many thanks to the other posters for their help.
     
    Last edited: Feb 1, 2010

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