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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, 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?

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

  • I am wondering: According to Goodle your car has a separated tank (the driveshaft divides the tank). That mandates a "nice" complicated dual fuel pump system: Does also the secondary pump got replaced? I assume there must be also also at least one coarse fuel filter in the tank. Did you already inspect those things? (Under your rear seats there ought to be the tank maintenance lid) – Martin Sep 28 '17 at 10:58
  • Ah, there's neither an additional pump or filter inside the tank. In fact, the flow from one part to the other takes place as a result of reverse pressure generated by the fuel filter (I don't know how) which is located outside of the tank, as the filter is. – Mikayil Abdullayev Sep 28 '17 at 11:04
  • can you confirm fuel pressure at the rail with a gauge and power at the pump? maybe put an amp clamp on the pump circuit see how many amps are being pulled. – Ben Sep 28 '17 at 13:01
  • I'll give it a try. – Mikayil Abdullayev Sep 28 '17 at 13:29
  • This sounds frustrating. I am not familiar with the Mercedes fuel system, but was wondering if this could be a situation where the fuel cap is part of the system allowing it to properly pressurize. I have seen similar issues where replacing a worn gas cap solves many fuel delivery issues. Just a guess. – CharlieRB Sep 29 '17 at 17:35
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Ah, it turned out to be the crank position sensor. It seems anything that I thought caused the car to start (like pushing the gas pedal, shaking the car or adding some fuel) were just coincidences. Or they somehow affected the sensor. Fortunately the car didn't start when I was at the workshop. The mechanic scanned the car while I was trying to start it and said it was the faulty sensor. He replaced it and the car started immediately. I've been driving it for 4 days and thanks God I haven't had that problem so far.

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