Air in fuel problems - C250TD (W202)

Discussion in 'Engine' started by mrtgrady, Jul 5, 2011.

  1. mrtgrady

    mrtgrady New Member

    Messages:
    2
    Joined:
    May 7, 2007
    Location:
    Fareham, Hampshire
    Car:
    C-Class Elegance 250TD (W202)
    I've been having problems with my C-Class starting. After visits from a couple of mobile mechanics it has been diagnosed as a problem with air getting into the fuel lines.

    The first mechanic replaced o-rings and pipes in the engine compartment but the second mechanic says the problem is with air entering the fuel from the fuel tank end of the system.

    As the fuel tank on the C250TD (W202) is a saddle tank the second mechanic says the car needs to be towed to a garage, lifted and then work can be done to sort it out.

    I've already spent over £500 on getting this far and the car is not worth much more than that. That said it's only done 135,000 miles and is in such good condition I can't justify scrapping it.

    Has anyone come across this kind of problem before and if so how was it resolved? If not does anyone have any ideas of whether I could attempt a fix on my own and what it would be?

    Cheers in advance
    Mark
     
  2. 142 TPL

    142 TPL Hardcore MB Enthusiast

    Messages:
    138
    Joined:
    Aug 30, 2009
    Common problem with the 250TD is the pipes and O rings not sealing, also make sure that the fuel filter is seated correctly and filled with fuel when fitting. Another common fault is the fuel draining back to the tank when left parked. This can be cured with a none return valve fitted to the feed pipe from the tank in the engine bay. With the saddle tank you need to make sure that the bleed off / return flow to the tank is sufficient to make the fuel transfer from one side to the other if this does not happen you with run out of fuel at 1/4 tank on the gauge. If you only have 1/4 tank in the car this could be your problem so try adding some fuel and see if that helps
     
  3. Dieselman

    Dieselman Banned

    Messages:
    34,206
    Joined:
    Jul 13, 2003
    Car:
    Peugeot 403 Convertible
    A likely point of air ingress is the fuel heater mounted on the cylinder head, another is the metal to rubber pipe connections at the rear of the engine bay.
     
  4. WG M-B

    WG M-B Auhorised Forum Sponsor Authorised Forum Sponsor

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    May 26, 2011
    Location:
    N/W london
    Car:
    C63 Wagon in black
    Times 2 ! The metal to rubber pipe connections are a very simple fix and very often get over looked!
     
  5. BlackC55

    BlackC55 Authorised Forum Sponsor Authorised Forum Sponsor

    Messages:
    18,741
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    Location:
    Horndean, Portsmouth, Hampshire, Southsea
    Car:
    C43 AMG with a 55 engine and supercharger, E55 AMG, S500, etc
    Also a non return pipe can be fitted to help keep the fuel pressure up to the filter.
     
  6. OP
    OP
    mrtgrady

    mrtgrady New Member

    Messages:
    2
    Joined:
    May 7, 2007
    Location:
    Fareham, Hampshire
    Car:
    C-Class Elegance 250TD (W202)
    Thanks for the quick replies.

    I'm pretty sure all the engine compartment side is fine - the guys who have been round so far were pretty thorough with that.

    I'm going to try to top up the tank to see if more fuel will help.

    I'm guessing though that the bleed off valve/return valve isn't something I can do myself on the drive?

    Cheers
    Mark
     

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