Timing is a pain on m119. I'm not a professional mechanic and I timed it myself. My first mistake was that I was trying to align camshafts with 4-5 degree mark on vibration damper. That was wrong. There is a clear 45* mark on damper. When I set it to 45* I had to turn camshafts to align all 4 cams so I could fit screwdriver into holes. But that was not it. Even though damper was at 45* I managed to align cams 2 ways. Holes would align but you can turn cam 180* and it would align still. So I had to envision which cylinder is at its intake phase and rotated cam for valve to start opening. Same with exhaust cams. After that everything aligned properly but before I had same problem as you have. I could only rotate the engine less than half way and it would stop.

Hope that helps and good luck

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1999 ML430 Silver 135k ml
Smoked LED taillights, Alpine in-dash DVD player, 12" sub, Pioneer components, 2 amps, 4200k HIDs, ML55 headlights, 20" rims, mirror LED blinkers

SOLD. 1996 E320 145k ml. Burgundy

SOLD but miss it everyday 1992 500sel Black
Chime buzzer mod,Alpine CD/MP3 player with stock amp,Euro headlights,S600 grill,20" rims, BEST CAR EVER!

SOLD. 1990 300E White
187k ml,smoked tails,Euro headlights,17rims,Intake,12" sub in first aid kit,alarm/autostart,buzzer mod