Hard to start and revs high when started
 

Need some help with a 1980 300 td wagon, its hard to start you have to put the pedal to the floor, and when it does start it revs high until you put it drive. It was converted to run grease but the system was removed before i purchased it. have found a sensor disconnected behind the oil filter at the flywheel i don't know if this is related to the problem or not?, i'm new to diesels and mercedes but i'm learning.

There are several possibilities on the high rev. First there is the idle control knob on the dash just under the instruments. It might be set way too high, and/or the linkage may be way out of adjustment.

On the hard to start, could be valves not adjusted properly, glow plugs not all working, compression low, old bad fuel.

Would be best to search on "hard to start" in the archives for that problem.

does not have throttle control, will idle for a little while then will rev up, i can slow it back down with the stop lever and it will idle again but revs up again after a little while.
Made a mistake in my first post its not a 1980 its an 1982

Yeah, the '82 won't have the inside idle adjust knob. Sounds like the linkage is mal-adjusted somewhere. Search on "linkage adjust" or something like that. You should find a thread with a link to a place that shows the correct linkage lengths.