300SD won't turnover

[Boinftw]

Long story short, '85 300SD, father-in-law's car, driven by his son. Son is driving the other day, says the car sputtered then quit and won't turnover. Not that it won't start, but it won't turnover. One guy gets out his 27mm socket and says the engine is froze. After reading alot on here, I highly doubt that's the case. Granted, it does have somewhere north of 400k (odometer broke several years ago.) I take of the valve cover and get my 27mm socket out and see what happens. I can move the crank, but only counterclockwise (toward the passenger side) a few degrees. Timing chain isn't moving, on the cam, but the tensioner is adjusting for the slack. Being such high compression, should I be able to really move the crank alot? Another question I'm embarassed to ask -- shouldn't I get some movement in either direction, and which direction is the correct rotation? I'm still trying to procure a good manual for this car, but I gather that the fuel pump/rail/distribution is driven off the timing chain as well? Would it be possible for the fuel system to lock up and not allow the crank to turn in that direction, since the chain wouldn't have any slack between the pump & the crank?

Lots of questions and there's alot I don't know about this car. I'm somewhat used to my 87 190E, but this is for sure a different ballgame. Thanks in advance for any thoughts & suggestions.