Mercedes-Benz W210 CDI does not start cold
The W210 CDI does not start cold - what is the most common cause?
The most common cause is air in the fuel system. Look in the transparent fuel hoses to see whether air bubbles travel in them. If they do, replace the leaking O-rings: the seals of the filter cover, the hoses leaving the filter and the injector return connectors.
Can injector return leakage prevent the W210 CDI from starting?
Yes. If an injector leaks too much to the return side, the rail pressure does not rise and the car does not start cold or in frost. The return leakage test is done with a completely cold engine. A leak of more than 20 ml/min means the injectors are worn out.
What other parts can cause poor cold starting of the W210 CDI?
The seals of the high-pressure pump or the O-ring of its pressure control valve can leak, and the pump can also leak internally. For intermittent starting difficulty it is also worth checking the camshaft and crankshaft position sensors; oil can get into the connector of the camshaft sensor.