brohndog,

Try using the search function. Starting these beasts under certain circumstances is a challenge we all have in common. In general the problems, assuming the piston to cylinder wall interface is good and compression is acceptable, usually lie in the glow plug system, the starter and electrical system, or the fuel system. With glow plugs the issue is usually a bad plug, in which case you typically but not always, get a signal from the glow plug indicator light - it will light inconsistently or blink or do some other abnormal lighting event. If the problem is with the starter it is usually because the starter is aging and with the design voltage will not produce the design torque to crank the engine over at the design speed. Low speed on the starter means the heat of compression is sucked into the block before the air temperature reaches a value high enough to support ignition of the fuel. This problem can be more of a problem in warm weather than cold weather depending on the way the starter motor is deteriorating. Real age is an insulation abuse state from accumulated long starting cycles of the starter, and this gets worse with temperature. If the charging system voltage is low while starting, you have a bum battery or a bum alternator. And, if the fuel system is leaking at all, you likely are getting air into the system, and the fuel system is not prepared to deal effectively with air instead of Diesel fuel. The system must purge itself to work correctly and it is very inefficient at doing this by cranking the engine with the starter. This problem goes unattended to and pretty soon the starter and battery are weakened.

All this stuff is interrelated. A borderline starter will work ok if everything else is top notch. But any combination of weaknesses can lead to starting woes that are very difficult to get your arms around. A new starter will not, for example, fix a starting problem if the glow plugs are not functioning and you have a small air leak. Or a bad battery. And so on.

Try the search function. We have experienced nearly every possible system weakness permutation and posted about it here. Good luck, Jim

__________________
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)