I hate to sound negative, but trying to adjust the timing while the engine is running is not a good idea. The drip tube is fairly inexpensive and you could even make one out of tubing. Although your idea to check the fuel timing and adjust it to specification is something worthwhile, you need to face up to the fact that it may not solve your problem. Your problem could be bad injectors or just timing chain wear.

IMHO you need to at least get a Haynes manual and then start your troubleshooting tasks. Make or purchase a drip tube to check the timing, and then eliminate the other issues one by one. You can get the injectors tested at a diesel shop for a small amount (mine were done for free).

Good luck.

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1976 240D
1987 560SL
2007 E320 Bluetec
1998 C280 (now son’s car)
1982 240D Manual - Sold