1982 300SD W-126 injection timing

I/P timing seems to wonder when checking. Car ran fine but in the quest to make sure my timing is set to 24 BTDC I noticed that it was moving around. I thought timing chain stretch so bought the kit, installed and I/P timing still moves from between BTDC to ATDC. I'm not able to get it even close to the correct timing spot. Help!!

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Diesel Engine Specific Aid

Chassis Model Number

W126

clarify

What type of timing method are you using?

1982 300sd I/P timing

I use what is published in your booklets. I believe it was the diesel engine performance booklet. I'm 1 hr from 2 mercedes shops and there no help what so ever. If they can't hook it up to a comp. they can't tell you what is wrong lol!

Couple things to consider

Any fuel restriction or air getting into the system could cause variation.

New Filters? New hand primer pump? new or good hoses and clamps? Hold the throttle wide open when checking? When you opened up the delivery valve was there any rust or crude it in? You could have a problem with the check valves in the lift pump allowing fuel to leak back when trying to turn the engine over by hand. Use the hand pump to make sure there is pressure in the fuel system just before you test.

1982 300sd I/P timing

filter new,primer is older, good hoses, I'll try the throttle wide open , after removing the delivery valve it was clean When using the hand pump, fuel squirts out with pressure. When delivery valve spring is removed you can't get much pressure (if any) built up is that normal?