I would do atleast a valve clearance check. Cold setting is .004" intake and .012" ehxaust. You would be suprised how a slightly tight valve can affect starting. The other thing I would try is TOW STARTING the car. This gets the engine turning faster than the starter will. I did this to a '79 300D that had sat a long time. It just wouldn't catch with the starter.
Tow the car to about 35mph for a quarter mile or so to get the trans pressured up via the rear pump. Turn on the key to ON position and select the shifter to "S". This will turn the engine over and it should start. Idle the car down until the glow relay lets go then drive the car awhile.

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My Truck.. 2007 DODGE, 5.9 Cummins, 6spd stick, 4X4. My car..1977 240D, OTHER WHEELS...1955 VW Oval window bug, European Delivery (Holland) with a 1700cc, 2 barrel, Porsche drum brakes. 1939 WILLYS Pick-up. 1967 Triumph 200cc Tiger Cub. 1976 Honda 550F 4cyl Motor Cycle.