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c250 not starting

Discussion in 'Engine, Drivetrain, Fuel and Exhaust' started by will1987, Jan 1, 2013.

  1. will1987

    will1987 New Member

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    Location:
    ireland
    Your Mercedes:
    c250
    hi new to this and looking for some advice im running the car on vegetable oil and it died on the motorway so i got the car home put diesel in and changed the fuel filter it still wont start any advice would be great
     
  2. chizzel89

    chizzel89 Senior Member

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    Pembrokeshire
    Your Mercedes:
    Mercedes-Benz C250 Turbodiesel Sport Auto. Estate. 1998. 180,000 mls
    How much fuel is in the tank?

    If it is at half tank or lower, then you may have encountered one of the main problems with running these cars on heavey oils like veg oil. Also is it likely you need to replace all the O-rings on the fuel pipes which are causing fuel to drain back to the fuel tank.

    There are two fuel tanks either side of the prop shaft joined by siphoning balance pipes.

    When hot oil is returned from the engine (in great quantities- these engines draw a lot of fuel), it fills up the tank on the opposite side from where cold, heavey oil is being drawn.
    The hot runny oil is much lighter per litre, so you end up with the return tank full of hot runny oil and the feed tank running dry.
    Liquids of dissimilar viscosity don't balance.
    Trying filling it up until the fuel gauge is on the max.

    THen it will take 20-30 seconds of cranking to reprime the system. Do 6 second bursts.

    You'd be well advised to do some more preperation on the engine and fuel system if you intend on running high veg oil blends/ pure. If you don't you will at some point get lots of fuel leaks from the knackered O-rings which cant handle the extra stress of veg oil and later on you may get gummed piston rings (usually after tens of thousands of miles). Also make sure your glow plugs are all good. If the light stays on after the engine starts- they need attention.
     
    Last edited: Jan 1, 2013
  3. OP
    will1987

    will1987 New Member

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    ireland
    Your Mercedes:
    c250

    hi thanks for the reply i filled up just to 3/4 full and turned it over still wouldnt start i took off the diesel filter to see was there fuel coming and nothing?
     
  4. chizzel89

    chizzel89 Senior Member

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    Your Mercedes:
    Mercedes-Benz C250 Turbodiesel Sport Auto. Estate. 1998. 180,000 mls
    The diesel will be sitting on top of the veg oil in the tank and in any case the fuel lines/ sender will probably still be full of veg oil.

    What is probably happening is that the worn O-rings on the suction side of the lift pump are letting in air so badly that they are preventing any fuel being drawn up to the injector pump.

    As a get out of jail free card you could cut into the fuel feed line (the thicker of the two fuel hoses which join metal pipes at the passenger side inner wing in the engine bay- inlet manifold will have to come off) and fit a manual primer bulb. This will allow you to prime the system without loads of cranking and also stop the fuel draining back to the tank, though it will probably be too restrictive for high speed veg oil use.

    What you really need to do is replace all the O-rings on the clear pushfit fuel pipes, the O-ring behind the fuel shut off valve, the O-ring on the fuel pre-filter and possibly the rubber fuel hose connecting the fuel heater to the metal lines on the inner wing.
     
  5. Some guy on the internet

    Some guy on the internet Senior Member

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    Your Mercedes:
    A few.
    You need to replace the air in the system which was introduced when there was no fuel coming through with fuel.

    Just remove the pre filter (right next to the main filter) & carefully pour diesel into the chamber while someone turns the ignition key. It'll start after you refill the small chamber 3 or 4 times, less than ½ a litre should do it. After about 3 tries use the throttle control cable in the engine bay to help it to start.

    If you are running on SVO or WVO I'd fill it up before it hits the quarter tank level. Some people dilute the fuel with 5-10% RUG which thins it to help starting & to avoid the saddle tank problem.
     
  6. chizzel89

    chizzel89 Senior Member

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    Your Mercedes:
    Mercedes-Benz C250 Turbodiesel Sport Auto. Estate. 1998. 180,000 mls
    Good point. These cars need a LOT of cranking to get all the air out if you don't fill up the filter with diesel.
    If the battery isnt tip top and cranking speed is down it could take all day and possibly still not manage.

    In these temperatures, half tank mark is when you want to think about filling up. On high speed runs I have run out nearer the half tank mark than the quarter tank mark.
     
  7. OP
    will1987

    will1987 New Member

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    Your Mercedes:
    c250
    ok got it running with a can of lynx sprayed it into the inlet and bang she fired up seems to running fine now
     
  8. chizzel89

    chizzel89 Senior Member

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    Your Mercedes:
    Mercedes-Benz C250 Turbodiesel Sport Auto. Estate. 1998. 180,000 mls
    Sounds like you ran out of fuel on the motorway due to the saddle tank phenomenon and then couldn't get the air out.

    Carry a can of diesel in the boot all the time, or always keep it above half tank.
     
  9. chizzel89

    chizzel89 Senior Member

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    Joined:
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    Your Mercedes:
    Mercedes-Benz C250 Turbodiesel Sport Auto. Estate. 1998. 180,000 mls
    They are great cars though aren't they. I manage to get the speedo on the stopper on the motorway once running on WVO- easily its billed top speed of 125mph. That is good engineering for a car to be able to manage that after 180,000 miles whilst running on the wrong fuel!
     

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