Jim,
'Sorry to hear about your motor.
psfred and everyone else are correct ,there was something wrong with the
original rods ( + maybe the secondary sets).
I had a parts person read to me over the landline a side note from mercedes
parts 'fische "never to use the rods with the original rod part # again" .
A southeastern mercedes engine rebuilder has seen too much co-relation
between non functioning glow plugs and bent rods on these motors.
(his theory is: too much raw fuel dumped into a cold cylinder @ startup
= hyrolock...)
Many ideas have been proposed.

I have a note top myself ( too many notes , too much disorganization)
about rod(S) # 603 030 3120 , but I can't remember if this is the final
permutation of part #'s for the 603 or the 602.