Confirm that the engine isn't seized before attempting to start it by putting a 27mm socket and breaker bar on the front of the crankshaft. Turn the engine in direction of normal rotation not backwards. If it is seized do not try to break it free with the starter, things will likely break internally.

The '74 240D also has an oil bath reservoir on the injection pump, they are not pressure oiled. Confirm that the injection pump has oil in it before starting it. If it turns and their is oil in the pump, change the oil and filter and possibly even the oil in the injection pump.

Step carefully, a 49k mile car maybe a gem. Avoid doing damage by rushing to start the engine.

Good luck!!!

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer