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  1. #1
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    Dirty tank or bad fuel pump

    I have 2000 c240. I've been struggling with starting problem for the last 5 days. The story began when I couldn't start the car after driving for 5 minutes. I turned on and off 4-5 times after which the car started. Then one day, when I was at lights, suddenly the engine died. Didn't start unless I pushed the gas pedal. A mechanic told me that your throttle body needs to be cleaned. So I got it cleaned and thought it was done. Then yesterday, while parking, the car stopped and I couldn't start it any how. Then a nearby mechanic tried adding just 100ml of gasoline and car started immediately. The tank was nearly full. He said it might be the fuel pump or your tank is so dirty that doesn't let fuel out. This morning, I started the car normally, headed to the gas station, filled up the tank and guess what, car didn't start. I got stuck right in the station. So adding more gas didn't help this time. Then a guy offered to shake the car on the rear about 10 times. We did it and the car started. I left it idle for 5 minutes and again it died. Then we shook again and the car started again. I took it to diagnostics. The crankshaft position sensor along with other engine related stuff was all right. But the computer showed some trouble with fuel pressure. The guy told me that it's something with your tank or the fuel pump.

    Now, how do I know whether it's the tank which is dirty, clogged filter or it's the fuel pump fault? I replaced the pump(Bosch) and filter(Hengst) 7000 km earlier. Do you think I have to get the tank removed? Besides this, if it's the fuel pump, how do I know if it's the pump itself or the relay?

    Note: Engine never dies at high revs or high speeds. It feels like the reverse is the case.

  2. #2
    Senior Member kowalski's Avatar
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    did you try adding a STP fuel injector cleaner in the fuel tank?
    this is the cheapest solution to do first
    maybe your injectors are clogged?

    when your fuel tank is very low on gas you can add a bottle with STP fuel injector cleaner, then fill up with 2/4th of gas approx 20-30L of fuel, full tank is 62L
    see if this solution helps with better starts?

    if your fuel tank is dirty, gasoline might be very filthy at your gas stations?
    what gas do you fill?
    unleaded standard 95 octane or 98-99-100 octane super blei frei?

  3. #3
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    I've always filled 95. Do you have any idea why the car would start after shaking it?

  4. #4
    Senior Member kowalski's Avatar
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    did you read codes?

    have you noticed any broken rubber hoses around engine?
    did you lift of the airbox at any time, when refitting maybe airbox not sitting right ontop of MAF?

    maybe bad spark plugs?
    maybe bad coil packs?
    maybe bad earth strap?

    check with flash ligth if you notice anything strange around engine?

  5. #5
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    I've done everything you mentioned. Computer doesn't show any trouble with around the engine. The only trouble code was the the fuel pressure fault. I'll lift it up tomorrow and see underneath. Maybe the pump relay is also going bad.

  6. #6
    Senior Member kowalski's Avatar
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    when you turn on the ignition do you hear fuel pump buzz or maybe you don't hear anything?
    if pump is buzzing pump is working.

    find fuses and see what they look like?

    you don't mention how many km's your car have on the clock?

  7. #7
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    Change the fuel pump.

  8. #8
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    Quote Originally Posted by kowalski View Post
    when you turn on the ignition do you hear fuel pump buzz or maybe you don't hear anything?
    if pump is buzzing pump is working.

    find fuses and see what they look like?

    you don't mention how many km's your car have on the clock?
    When I turn on the ignition, I can hear the buzzing sound. Although it's 17 years old, it's only got 118k km's. I bought it from Germany with 73k on it 4 years ago. And I myself drive 10-12k per year.

    Anyway, it turned out to be the crank sensor issue. On Saturday morning I took it to a mechanic. As always in the mornings, the car started normally. He first replaced the pump relay and asked me to drive a little and see if I had the same problem again. But I asked him to check the crank sensor before I move. Because he said he had the chance to inspect the sensor outside. He asked me to wait for the engine to cool down so that he could access the sensor. Only 20 minutes later a guy asked me to move the car ahead to make space for him. I tried to start the car but car wouldn't start. That was just the time because I hadn't been able to reproduce the problem when I was at the workshop. He asked me to try to start the car again and listened to the pump and said the pump was ok. This way we opted out the case with pump relay too. Then he setup the computer scan and again asked me to start and voila. He said the problem was with the sensor. He replaced the sensor and car started.

    Now, to be honest I'm still concerned because of two reasons:

    1. If the sensor was bad, the why didn't he see the fault code before? I know that bad sensor drops fault code.
    2. Another guy who scanned the car before, said the only issue the scan showed was the fuel pressure.

    Since Saturday, I haven't had any problem thus far. I hope that indeed was the issue, which I hope has been fixed.

  9. #9
    Senior Member kowalski's Avatar
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    bad CPS only occurs when engine is hot, so the next time you started your car, car didn't start until engine cooled down.
    this is a sneaky problem with bad CPS sensor.
    you could have been left stranded on deserted road in no man's land if CPS had broken down, then you had to call a tow truck?
    lucky for you problem showed up at the shop.

    did you go to a shop who uses proper MB code reader?
    if you go to a shop using clones maybe error codes are not shown or accurate read on computer?
    your car does it have the OBDII, came on MY2000 or the old style 38 round pin connector which 1998-1999 cars have?

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    Quote Originally Posted by kowalski View Post
    did you go to a shop who uses proper MB code reader?
    if you go to a shop using clones maybe error codes are not shown or accurate read on computer?
    your car does it have the OBDII, came on MY2000 or the old style 38 round pin connector which 1998-1999 cars have?
    It was an independent shop and I don't think they have a reader that is specific to MB, so yes, what you said about inaccurate reading might be the case. the car doesn't have OBD2 port, only 38 pin old port. It was made for European market, so I think unlike the ones made for US market, there was no obligation to supply cars with OBD2 ports at that time.

  11. #11
    Senior Member kowalski's Avatar
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    you have a MY2000, does it have tiptronic transmission?
    the 2000 also got CEL in cluster (engine symbol - check engine light) I would have assumed it also got the more modern OBDII?
    the North American market cars had the OBDII because they had CEL.
    not sure if US cars had the OBDII on 1998-1999 cars?

  12. #12
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    I haven't been able to solve that mistery: Is my transmission tiptronic or just electronic. It's got + and - sings after D. There is a CEL in the dash. But no obd2

  13. #13
    Senior Member kowalski's Avatar
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    you have the best updated transmission tiptronic for +/- shifting.
    see behind the steering wheel, you have one button on each side, for up and down shifting gears when you don't use the stick.

    next time you see the CEL in cluster, something is wrong with your car, take it to shop and read codes!
    1998-1999 euro cars never had CEL in cluster which was stupido!

  14. #14
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    Red face

    Quote Originally Posted by kowalski View Post
    you have the best updated transmission tiptronic for +/- shifting.
    see behind the steering wheel, you have one button on each side, for up and down shifting gears when you don't use the stick.

    next time you see the CEL in cluster, something is wrong with your car, take it to shop and read codes!
    1998-1999 euro cars never had CEL in cluster which was stupido!

    I'm afraid there's no button behind the steering wheel. It's just the wheel itself. I don't even have steering wheel adjustment, except for the telescope.

    When I said I had CEL light in the dashboard, I meant there was the icon for it, but it has never lit so far, thanks to God.

  15. #15
    Senior Member kowalski's Avatar
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    c43 amg from 2000 had shift buttons behind the wheel.
    do you have the same steering wheel smaller sporty type like on the c43 minus thick grip without perforated leather ontop?
    do you have SPORT trim on your car, then you should also have the smaller type steering wheel?

    I meant when CEL lights up in cluster there is something wrong with the car, you have to check codes.
    no illumination from CEL all is good with the car

  16. #16
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    Quote Originally Posted by kowalski View Post
    do you have the same steering wheel smaller sporty type like on the c43 minus thick grip without perforated leather ontop?
    do you have SPORT trim on your car, then you should also have the smaller type steering wheel?

    My car is Classic trim. So it's really stripped off. I wish I had that steering wheel.

  17. #17
    Senior Member kowalski's Avatar
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    Classic = it's basic and most economical version of them all.
    Classic - Elegance - Esprit - Sport.

    As long as you are happy with your car it's all good.

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