Hey dudes and dudettes, lets talk math and science! Cause you wouldn't own an older Benz if you couldn't do either!
I've come up for a basic equation for chain timed inline Mercedes diesels like the OM617A to determine where to set pump timing as it is added to timing chain stretch.

So, given that:

X=timing mark on crank pulley
Y=timing chain stretch
Z=Actual pump timing mark

X+Y=Z

In example:
If you have 6 degrees of timing chain stretch (-6,Y) and you put your crank on 24BTDC (24,X) then your pump timing mark would be a decently retarded (18,Z)

24+(-6)=18


This all seems easy enough, except I believe there's a variable number (a W if you will) that needs to be combined with the (Y) timing chain stretch in order to lessen its value, for timing chain stretch does not wholly equate to full degrees.
Any members who can lend a hand in determining the validity of this equation, or provide info on W and other variables, are strongly encouraged to help out. I thank you in advance!

Hc:

To correct injection pump timing for a "known" number of crankshaft degrees (y*) of timing chain wear (aka, "stretch") as observed at the camshaft, advance the pump timing by y*/2. Why y*/2? Because the pump sprocket is ~ 1/2 the distance, as measured in chain pitches, from the crank sprocket to the cam sprocket.

Good discussion. But, seems off track. You want to time the IP to the crankshaft, i.e. where the piston sits. If you set the crank mark at 24 BTDC, you then adjust the IP to the exact "start of delivery" (i.e. inlet valve on IP first closes). There are no marks on the IP to tell you the timing chain stretch between crank and timing sprocket.

The marks you must be referring to tell you the stretch between crank and camshaft. That affects valve timing. You can adjust that out by using an offset key on the cam sprocket, which is fairly easy (just block opening so you don't drop anything down the timing chain cavity. I used an offset key (smallest choice) in one of my 300D's.

In my two 300D's, I adjusted the IP to 27 deg BTDC, since supposedly better performance. I didn't notice a difference. Anyway, after another 200K miles, it will probably have worn back to factory 24 deg.

__________________
1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans

Why over analyse and complicate things. Just do it by sound and "feel"! Pump rebuilders will often tell you the degrees as well.

__________________
1978 300D, 373,000km 617.912, 711.113 5 speed, 7.5mm superpump, HX30W turbo...many, many years in the making....
1977 280> 300D - 500,000km+ (to be sold...)
1984 240TD>300TD 121,000 miles, *gone*
1977 250 parts car
1988 Toyota Corona 2.0D *gone*
1975 FJ45>HJ45
1981 200>240D (to be sold...)
1999 Hyundai Lantra 1.6 *gone*
1980s Lansing Bagnall FOER 5.2 Forklift (the Mk2 engine hoist)
2001 Holden Rodeo 4JB1T 2WD