Mercedes OM616 OM617 OM615 engine setting the injection pump timing

Mercedes OM616 engine. I was trying to fix the hard starting. I had to like preheat 2 minutes, and try 3 to 4 times to start and sometimes it drained the new battery so hard that I could not start the engine at all. I started by doing the valve adjustments, at the same time I took out the injectors to have them inspected, they said they were not good, so I replaced the injection nozzles. I also too out the Bosch injection pump and had the manual pump changed. Now upon putting the Bosch injection pump back, setting the crankshaft at 24BTDC and having the mark on the injection pump teeth aligned, the engine would not start at all! Now, each time. you take out the pump for timing and getting the air out, each time it's close to taking 45 minutes. Now my mind started to play with me, about the degrees, at second thought, I adjusted the timing to 28 degrees, for chain slack, but nothing. It took me literally 2 full days from taking the pump out and back. I was getting desperate and spoke with a Mercedes garage to have it possibly towed to them. But they said at 24 BTDC it should start. Here is the key: From day one I thought about the chain slack, but nowhere online is anyone giving a solution, There were some forums were people were asking, but the answers were always beating around the bush or straight: "you have to replace the timing chain" and nothing else. I was considering to change the timing chain, but not right now, why could no one give a straight answer? So after not listening about the 24 degrees BTDC and do my own thinking I came up that when I align the cam shaft marks and check what I read on the crankshaft, in my case 6 degrees AFTER TDC (+6 degrees) and - 24 degrees is 18 degrees. As soon as I did that, the engine started right away. Now with the new nozzles and valve clearances done, the motor starts the way it supposed to, little preheat and starts with the first crank. I was also almost going to replace the starter motor thinking that it did not rev the engine strong enough to create compression. I am telling you, after a while your mind is playing with you. Another tip is also to really write down the previous teeth positions of the injection pump and what you tried before because you forget what you did after doing so many adjustments. Anyway, thanks for watching.Your opinion is appreciated.

[@valparaisosting]

Hi friend, i still don't understand how you compensate pump timing without an exact tdc, but it works😂

[@Bauerofficial]

He accouted for the slack of the chain, apparent by checking how misaligned the crankshaft is to the camshaft at its tdc marks. I suggest replacing the chain though, as 6 degrees is a lot.