Mercedes-Benz C220 CDI (W204) blowing black smoke

I own a 2009 Mercedes-Benz C220 CDI (W204) with an automatic gearbox. I have recently had a problem where the car is blowing out black smoke and the car has also stalled a few times at low speed, which is weird for an automatic. I did have a problem few months ago where I got an error code advising "fuel rail pressure is too low". I booked the car in with Mercedes Birmingham and they carried out diagnostics and told me the car appears to be fine.

I have always serviced the car at Mercedes and am now concerned about the black smoke. I have looked online and found a few forums that suggest it could be the fuel pump followed by fuel injectors followed by fuel filter. I don't think the fuel pump is faulty as I can hear the mechanism sound when I quarter turn the key. Can you offer any help?

Asked on 24 May 2014 by Asif

Answered by Honest John

There are two fuel pumps. A low pressure 'lifter' pump in the fuel tank, and a high pressure injection pump. The fuel filter is between them. If the low pressure pump fails then fuel will not reach the filter and the engine. Diagnostics never show faults with the low pressure pump, only that there is low fuel pressure before the filter. Other possibilities are a work injection pump due to lack of lubricity in the fuel used, and failed injectors. Or failure of the turbo bearing oil seals or valve stem oil seals. I'd discount the latter two because they would result in fairly permanent black smoke. So I think the problem is most likely with one or more injectors or with the injection pump.

Tags: technical issues smoke fuel pumps

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