When you acquire an older Mercedes diesel or even gas passenger car for that matter, the first thing you want to do is determine the internal health of the engine. Don’t throw a lot of money at other repairs or parts until you make sure you have a strong and healthy engine. You do this by removing the valve cover or covers, inspection the cam(s), adjust the valves if applicable, and THEN check your internal engine timing. You may never get the engine to run right with excessive timing chain stretch and you risk the chance of having the chain break and destroying the engine. Kent will go over the procedure in this video of checking the engine timing on a 1976 Mercedes 240D.