On average fuel injectors last about 100,000 miles at which one of two things may be wrong with them: the spring may be weak or the nozzle may be compromised. If the injector is spraying a solid stream of fuel instead of a mist it may melt your piston. If the spring is weak the engine will be "nailing" that is pre-igniting similar to a gasoline powered car "pinging" or "pinking". It's must louder when it happens in a diesel and sounds like a sharp metallic knock. A car with a bad injector can be expected to smoke and or give poor performance and economy.

Unlike Mercedes gasoline fuel injectors you can replace just the nozzle if the injector is otherwise ok. You can have them tested; order any replacements for defective injectors and a set of nozzles. Have your injectors rebuilt and matched to within 5 psi. 1 psi if you can get it but not many places can do this kind of accuracy. Just buy a new set of injectors if you don't want to be running all over town with them in your car. Order a meter of cloth braided return hose too, the proper German stuff, not generic black vacuum hose which will not work.

To remove the injector first disconnect the metal fuel line to the injector then with needle nose pliers take off the return line. It's ok to destroy the return line when you're taking it off as you're installing new lines. Now use a 27mm socket and remove the injector just like removing a spark plug in a gasoline powered car.

Installation is just the reverse of removal; be sure to torque them to factory specs, prime the pump and start the car. New/rebuilt injectors sound louder than tires ones s be prepared for the odd situation where a car in good shape has more diesel klatter than one that needs attention.

Richard Sexton