The right way to do it is with a device that compares the IP timing mark with the crank pulley timing mark. Some call device an A-B light tool.

The probably good enough way to do it is to use the MB tool that locks the IP in position for removal and installation. $30-50 depending on where you shop.

Some claim to eyeball it using a mirror.

In the absence of the A-B light, essentially you set the crank to 15 ATDC of #1 and adjust the IP so the locking tool slides in, or until you see the timing cog centered in the IP inspection hole. If you go from TDC to 30 ATDC without seeing a cog, give the engine another full turn as you're on the #6 phase of the motor. Pull the valve cover to be sure if you're not lazy like me. this also gives you a chance to check timing chain stretch. TURN THE MOTOR ONLY IN THE DIRECTION IT TURNS WHEN RUNNING. If you get to 16 ATDC, turn it another 719 degrees.

I have no problem turning the 400psi motor without relieving compression and I'm frail as DIYers go.

The IP inspection hole is on the US driver side of the IP under a 17mm head plug. Up to a teaspoon of oil can drip from the inspection hole when you remove the plug. No need to refill, just check the engine oil level when you're done.

The IP is held by 3 13mm head bolts in front and 1 13mm head bolt (maybe a nut) in the back. The 3 bolts in front are kind of difficult to see and more difficult to describe. The bolt in the back is almost to the glow plugs. All the bolts are parallel to the crank.

With the IP loose, turn the 8mm head bolt at the front of the IP where it meets the block. Turning the 8mm head bolt CW as viewed from above advaces IP timing.

Protocol calls for releasing the injection lines from the IP but if you're only off by 1 or 2 degrees... You should also check the throttle linkage after moving the IP.

You should know that the OM603 crank timing pointer can be installed to +/- 1.5 degrees of actual or something like that so don't take as gospel what you read at the crank. See why you need the A-B light?

Check this thread for more info:

603 IP timng lock tool

Sixto
91 300SE
87 300SDL
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