You can also determine approximate TDC of a piston in other ways such as looking at the cam shaft lobes - removing the glow plugs (which is helps turning the crank anyway) and feeling for air being forced out of the cylinder on the compression stroke - knowing that after cylinder 1 on an OM617 the next cylinder to reach TDC is #5 and then #2 then #3 then #4 (very different from the firing order!) and that these happen at a spacing of 72 degrees - alternatively you could rotate the crank shaft a whole lot more (twice as far) and find the TDC after each compression stroke by following the firing order often on the valve cover which is 1,2,4,5,3 here you need to turn the crank by 144 degrees between "each TDC"...

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!