03.02.2014, 13:04
I have been off this forum for some time, but for future reference, I though that I would now post the fix to this problem, which is common to all 400Cdi engines of c. year 2000.
The fault lies in the ECU and is caused by the faillure of a small surface-mount electrolytic capacitor, which seems to develop a high Electrical Series Resistance (goes bad). It is part or a switching DC-DC converter circuit, which then stops working.
The repair involves replacing this particular capacitor and requires disassembly and opening of the CDi ECU.
There is a story about sub-standard 'counterfeit' elecrolytic capacitors finding their way on to the market in the early 2000's and causing problems in all sorts of electronics from camcorders to televisions.. to apparently, now, engine ECUs.
Anyway, the ESR of these faulty capacitors gets worse with lower temperature and so the resulting engine fault may be more commonly seen in cold weather or early morning.
The repair proceedure requires a super-fine soldering iron and a replacement capacitor, which costs about 50 cents. However, there are several electrolytic capacitors on the board and for peace of mind I changed them all. The faulty one, however, does not appear to have recognisable brand markings and was found to be the same faulty capacitor in at least 3 different ECUs.
It's been nearly 2 years since the fix and still going fine.
For full details including the correct grade for the replacement parts, please PM me.
http://forums.mercedesclub.org.uk/showth...067&page=2
The fault lies in the ECU and is caused by the faillure of a small surface-mount electrolytic capacitor, which seems to develop a high Electrical Series Resistance (goes bad). It is part or a switching DC-DC converter circuit, which then stops working.
The repair involves replacing this particular capacitor and requires disassembly and opening of the CDi ECU.
There is a story about sub-standard 'counterfeit' elecrolytic capacitors finding their way on to the market in the early 2000's and causing problems in all sorts of electronics from camcorders to televisions.. to apparently, now, engine ECUs.
Anyway, the ESR of these faulty capacitors gets worse with lower temperature and so the resulting engine fault may be more commonly seen in cold weather or early morning.
The repair proceedure requires a super-fine soldering iron and a replacement capacitor, which costs about 50 cents. However, there are several electrolytic capacitors on the board and for peace of mind I changed them all. The faulty one, however, does not appear to have recognisable brand markings and was found to be the same faulty capacitor in at least 3 different ECUs.
It's been nearly 2 years since the fix and still going fine.
For full details including the correct grade for the replacement parts, please PM me.
http://forums.mercedesclub.org.uk/showth...067&page=2