Mad Mercedes,

Starters usually need to be rewound when they fail, and very few rebuild shops invest the cost of a rewind. If it is truly shot, and starting a Diesel is a huge strain on a starter, the insulation will have broken down from excessive heat. This gives the current a path to follow that does no work. And Nature likes to do that.

An electric motor for commercial use is designed to some pretty specific but flimsy standards. It will be rated at the maximum torque or power, depending on how the customer looks at it, for a given duty cycle, which is not emphasized most of the time. You have to be aware enough to look at that. Anyway, a starter duty cycle is pretty minimal for its life. Consequently they are not made to run in any duty cycle that approximates continuous operation. In your car and mine, they will see conditions that are max load long enough to try to reach a thermal equillibrium. Under those conditions the machine should be rated at about a quarter of the load. Heat losses in the starter stator winding are based on Ohm's law, and run at the current drawn to the second power (squared) so your starter, under serious cranking is seeing a temperature rise that can be harmful to the insulation. A rebuilt starter that checks out at room temperature for winding resistance to ground may not do well with heat as insulation resistance drops rapidly with temperature. This is why a lot of rebuild shops do not notice the stator is shot, or near shot. So, we Dieselers ruin starters faster than most others and when you buy a rebuild you need one done by a reputable source.

I have had very good luck with the starters for these cars offered by FastLane. I believe they are genuine Bosch rebuilds and they seem to last, and start a Diesel with no apparent strain. Be sure you order the heavy duty version, as all W123 240D and 300D are physically interchangeable, and I believe that holds for the W126 cars too. As time went on MB and Bosch built more capable starters for these cars, and the later models have what is known as a "heavy duty" starter. That is the one you want and I think it is listed for the 300D and 3000SD. I got mine via normal mail in a few days, and I have used their express mail service a few times where the item usually arrives earlier than expected.

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)