amptique,

Trouble starting one of these engines when they are fully warmed up is usually a problem with low starting rpm from the starter, and that is a consequence of how old, and how hard the starter has worked, over its life.

The issue with warm restart problems can also be caused by poor connections at the battery, at the battery ground, or the connections to the starter itself. So, I would check the connections first, since that is essentially free and you can do it at anytime you want, if you do it yourself.

Diesel starters typically see much higher loads, and crank longer than their gasoline engine counterparts. They therefore get a lot hotter from current flowing through the windings. Heat damages the insulation on the windings and when the combination of high ambient temps, a near end of life insulation condition and a Diesel come together, you can get the confusing symptom of a hard to start Diesel that is fully warmed up.

Is your car a manual? If so, try push starting it, and if it starts right up, the chances are the starter is weak and not reaching the critical minimum speed needed to get one of these engines to fire.

Be very selective about where you get your next starter. If you use FastLane (recommended) you will get a starter rebuilt by Bosch. That means it will have a new stator winding with new insulation that will last for a while. Also, get the one for the 1985 300D Turbo. It is called "heavy duty" while the one listed for the 1983 and earlier 240D is not. The starters are physically interchangeable and having a slightly more robust unit for the 240D will help you through the cold and last longer. Many rebuilt starters will have all the moving parts taken care of, but they will not pick up the insulation system degradation and will therefore not rewind the unit. They may dip it in insulation material, but that is not the same as rewinding as dipping will do little to help where the wire exits the slots, which is where most problems occur.

Good luck, and let us know how you make out on this one. 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)