Locating the OM616 and OM617 Internal Engine Timing Marks

These can be hard to see if your engine is dirty and you don't know the exact location

Why are these timing marks important? There are a number of reasons. You can make some BIG mistakes working on your diesel engine or almost any engine for that matter, if you do not know where the timing marks are and how to use them.

Problem & Solution

Common among these chassis:


The timing marks are critical for use in the following diagnostics and repair:

  • Determining how much your timing chain has stretched
  • Removing the camshaft and rockers
  • Replacing valve stem seals with the head on the engine
  • Removing and replacing the cylinder head
  • Injection pump timing
  • Replacing the timing chain
  • Complete engine teardown and rebuild

There are two key locations with alignment marks. 

The first is located on your engine counterbalance and is marked of in degrees of rotation (usually in 5 degree increment marks. There is a pointer coming off the engine block that points to the position of the crank in relation to top dead center (tdc) on number one cylinder. When the pointer is at zero degrees and both valves are closed (you can feel play in the rocker arm) on number 1 cylinder your engine is a TDC (with piston coming up on compression stroke). ( The marks will not tell you if you are 180 degrees off - you have to refer to the closed valves to confirm TDC. If one of the valves is opened then it means you are off by 180 degress of rotation.







The second location is at the front of the camshaft right behind the sprocket. You will have to remove the valve cover to see these marks. There a a v notch cut in the spacer that sits on the end of the camshaft just behind the sprocket. On the forward cam tower there is a raised arrow as you see in the picture below. The arrow should line up with the notch when the engine is on TDC and both No. 1 cylinder valves are fully closed








Related commercial vid.  Pulling off the head

Related part

timing chain kits