I think your problem is not serious, you simply need to get the delivery valves sorted out. For each valve, I'd recommend you replace the washer, spring, and O-ring.

Remember: CLEAN CLEAN CLEAN!!! Any junk that enters the system here will go downstream directly to the injectors and clog them. Use brake cleaner and toothbrush, then compressed air.

Remove one valve at a time, 'rebuild' it with washer/spring/O-ring, install and torque correctly (tighten to 30 Nm, loosen and repeat, then loosen and torque to 35 Nm and lock down). After each valve, start the car and see if the problem is fixed or if the injection pump is making a new racket. If the IP starts making a new racket, loosen that delivery valve and re-torque using above procedure (sometimes the IP body gets warped when tightening down the delivery valves).

No, your problem is not an IP timing problem; usually the IP only needs to be timed once, when the car is built, and keeps time perfectly for the life of the engine.

__________________
Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC