Mercedes-Benz W210 CDI: air in the fuel system
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The W210 CDI does not start or runs poorly - can air in the fuel line be the cause?
Yes. Air prevents the pressure from rising, so the diesel starts poorly, jerks or does not start at all. A common symptom is air bubbles in the transparent fuel hose between the filter and the pump.
Where does the air in the W210 CDI fuel system usually come from?
The most common leak points are worn O-rings at the ends of hoses and seals, and the pipe outlets of the injection pump, and a loose or incorrectly sealed fuel filter cover. The leak point must be repaired, otherwise the air returns.
How is air removed from the W210 CDI fuel system?
First fill the cup of the fuel filter with diesel and try to start; bleeding may take several attempts, because the transfer pump is mechanical. If the air returns, look for the leak. If the fault is not air, the cause can also be the high-pressure pump, an injector or the crankshaft sensor.
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