W202 5cyl non-turbl diesel burning fuel

Discussion in 'Engine' started by expat, Jul 24, 2011.

  1. expat

    expat New Member

    Messages:
    24
    Joined:
    Jun 1, 2010
    Location:
    Near Galway
    Car:
    1994 C250D Saloon
    I've been burning fuel of late, a lot of blue smoking coming out of the tailpipe and heavy smell of diesel in the air.

    No visible signs of fuel leakage in the engine compartment except for what I'm calling the "overflow line" that comes from a fitting at the front of injector #1 (closest to front of car) and snakes over to a fitting just in front of the fuel filter. This is a cloth covered line and the part of the line closest to the fuel filter, which is the farthest "down hill", is soaked with diesel.

    I removed the plastic head cover to get a better look at what is going on, and exposed the tops of the five injectors that all sit down in what I'm calling their own, individual "well". Each of the wells are full of diesel fuel although it doesn't look as if the fuel is overflowing out of the well itself. I see no evidence where it is overflowing the well and leaking down over the head into the engine compartment. In fact there isn't much of a diesel smell in the engine compartment but there sure is coming out of the tailpipe when the engine is running.

    Each injector has a fitting, front and back, has what looks to be a fuel line going into it on one side and then coming out of it on the other. I'm guessing this is some sort of overflow line.

    Starting at injector #5, closest to the firewall, there is what looks to be about a 2" fuel line coming out of the back side of the injector (closest to the fire wall). The fuel line has a steel plug in it. In front of injector #5 there is a similar line that is not plugged but comes up out of the "well" then then goes over to the back side of injector #4. A line comes out of the front side of injector #4 and goes to the back side of injector #3. This progression goes all the way to injector #1 where the aforementioned line that come out of the front of injector #1 goes over to a push-on fitting just in front of the fuel filter where, I'm guessing, it is recirculated into the system.

    Any ideas on what's going on here? Why are the "wells" are full? Why I'm burning fuel?

    As always your insights are welcome and appreciated!!!
     
  2. dingo

    dingo New Member

    Messages:
    2
    Joined:
    Apr 13, 2011
    Car:
    sprinter 312
    Strol into your local MB dealship ( don't start laughing ) & ask a metre of the spill return pipe . pull off the old rubbish & cut new pieces to fit ,they just pull off & push on . I have found MB stuff top notch and even used it on other makes of vehicle to replace their rubbish spill return .

    your excess fuel that would normally go back to tank is being wasted as the pools demonstrate . it is also an offence to knowigly use a vehicle that is leaking diesel fuel on the road ( bitter experience with VOSA )

    simple repair & easy to carry out
    good luck & best wishes:)
     
    1 person likes this.
  3. OP
    OP
    expat

    expat New Member

    Messages:
    24
    Joined:
    Jun 1, 2010
    Location:
    Near Galway
    Car:
    1994 C250D Saloon
    So I was overthinking it? I thought maybe one, or more, of those hoses was clogged but then since it recirculates through the fuel filter I figured it was "double clean". Pays to think simple first.

    Thanks very much for the advice!! Since I'm way out in the west of Ireland I'll call, since it would be quite a stroll, the dealer and have him mail out a meter of the hose.

    Cheers!
     
  4. mike_c250

    mike_c250 New Member

    Messages:
    4
    Joined:
    Jul 26, 2012
    hi guys, i wonder if expat ever solved this problem nor remembers how for that matter. my w202 C250 is doing the same. i replaced the pipes as pe instruction and cleaned off the excess diesel from the "wells". everything seems fine now. problem is the car has a hard start in the morning or after parking it for over 5hours.

    I took it to a diesel mech who said it was my glow plugs. i went bought 5 of them (at R120 each i.e. USD12 each). i bought after market ones which refused to fit :(

    So the mech took out the first 4 with ease and cleaned them. the 5th one is stuck. he says he cannot force it as it will most likely break which would be a problem as he would have to call some one out to remove it. we decided he doesn't.

    the car starts for a few seconds, idles roughly then cuts off. could this be air in the line as EDC light has gone on.
     
  5. OP
    OP
    expat

    expat New Member

    Messages:
    24
    Joined:
    Jun 1, 2010
    Location:
    Near Galway
    Car:
    1994 C250D Saloon
    This problem turned out to be multiple fuel line leaks. One of the injector overflow lines was leaking as well as one of the 'curvy' pre-formed plastic lines. We got that all changed out and viola!, problem solved. But it looks like you've changed all those so possibly you've got other issues?

    As to your glow plugs, I did have a glow plug problem later on. One went bad. But it would still start, sometimes a bit cranky, but would get going and then run fine all day.

    Sorry I couldn't be of more help. Not enough of a mechanic to postulate about air getting sucked into your system. You'll get an answer though as there are some absolute engine geniuses on this forum.
     
    Last edited: Aug 31, 2013
  6. guydewdney

    guydewdney MB Enthusiast

    Messages:
    2,903
    Joined:
    Feb 14, 2004
    Location:
    Porlock, Zomerzet
    Car:
    906 Sprinter 313cdi
    mike - this is air in the injection system. change the clear 8mm diameter diesel lines like expat has done, about 50 quid for the lot, and ten minutes to fit. Check the top of the inj pump where the hard lines come out, theres a splined fitting at the end of the lines. clean this area. check after a run if theres any fuel on the flat bit of the pump - if so, the splines need undoing and the seals underneath replacing. two hours as you need to remove the inlet manifold. be VERY clean if you do this - I jetwashed the area first.
     
  7. spoton

    spoton Member

    Messages:
    38
    Joined:
    May 14, 2012
    Car:
    S202 1998 2.5 diesel estate
    air

    your problem does sound like air but air shouldnt put the EDC light on ,

    you can change all the clear fuel hoses however a cheaper solution can be to just change the O rings either end of those pipes, at the same time replace the prefilter O ring seal and the O ring that seals the fuel solenoid to the side of the injection pump (held on by 2 allen studs)
     

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