GANIMAL,
This subject has just been addressed in some other threads in pretty good detail. If you try a search on cold starting you should find a lot of information.
The issue is that in cold weather the block is a very large heat sink, and if the engine spins too slowly the heat of compression, which the engine relies on to heat the air in the combustion chamber to a temperature sufficient to ignite the fuel, is absorbed by the block as quickly as it is generated. Also, all the normal compression leaks have more time to leak the pressure being generated by the piston motion away.
There are many things that cause the starter to lose its ability to spin the engine over fast enough. The age and use history of the motor in the starter is one, as lots of long cranking episodes will get the starter very hot. Its rating is based on running for a few seconds at a time, with substantial rest periods between starting attempts which keeps the motor windings cool. Lots of repeat, back to back starting cycles will drive the winding temperatures up above their design limits, which will degrade the insulation system and lead to degraded performance.
Another reason a starter will not provide the torque needed to spin the engine fast enough is a poor charging system and/or battery. As will a heavier weight oil since the starter motor is also providing the torque needed to make the oil pump work. The added drag of a more viscous fluid will increase the load on the starter motor.
So, if you have no problems starting in warmer conditions, you probably do not have any serious internal to the engine problems. But, do a search and look at all the possibilities. Good luck, Jim
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Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles
Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)
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