Here is what Frank Barrett says about the Bosch fuel injection in his illustrated buyer's guide:
"Used regularly, mechanical fuel injection is reliable. Nonuse typically cause dried-up seals, corrosion in the injection pump, and more."
The Bosch fuel injection pump usually lasts 100,000 miles before needing overhaul, which is best left to specialists. Keep yours away from anyone without proper equipment and experience."
Frankly, I don't know anyone DIY'er who can work on fuel injection. I think it is an item like automatic transmissions - should they brake, you leave it to a specialist.
Having said that, fuel injection is far superior to carburation. I know Cap'n believes he has trouble with his 300E's fuel injection system, but I believe the facts prove that Mercedes fuel injection systems are incredibly reliable.
Come to think of it, it is quite hard to find any fuel injection related complaints on this site.
2001 E430, Bourdeaux Red, Oyster interior.
1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".