Regarding new injector seals - purists say yes, cobblers say no..... but if they leak it will be really obvious. Gotta torque em too and allign the seals carefully.

Maybe somebody here who has seen an injection pump go bad can advize you better than me. I've honestly never seen or heard of an MB/Bosch IP that failed.

Another culprit could be the ignition coil causing feeble orange spark instead of blue. And another often ignored 2 bit item is the condenser...... yes a bad condenser can stop an engine from starting.