Maintaining the fuel injectors is quite easy; there are only a few moving parts. You will need two wrenches to fit the two parts of the body of the injector.

Once you take the unit apart there are only 5 easy to handle parts inside. A small washer shaped disk which varies in thickness and along with a heavy spring, controls the pressure of the ejected fuel.

This fuel is then forced into a cylindrical nozzle which contains a needle like pin which opens and closes to produce the spray pattern of the ejected fuel.

I have had seven MB diesels since 1962 and have always done the injector maintenance. In all that time, I have only had to replace one pin and nozzle assembly.

The main problem, is a carbon buildup at the tip of the nozzle. This can be removed with a very fine brass bristled tooth brush. This looks just like a tooth brush, but has fine bristles made of brass. Or you can use the finest emery paper you can buy. You must then clean the tiny orifice at the bottom of the nozzle. I do this with a wooden toothpick, never do this with any metal tool. This orifice must mate perfectly with the nozzle pin or the spray of fuel will not be turned off instantly, causing dribbles of fuel at the end of the pressure cycle. I then clean all the parts of the injector in lacquer thinner and blow them dry with a low pressure air hose. (Before re-assembly, I soak the nozzle parts in clean kerosene or diesel fuel, this is needed because the lacquer thinner strips all lubrication from these very close tolerance components). The only care in reassembling them, is that you do not introduce any dirt into the nozzle assembly, or get oily fingerprints on the nozzle components.

I have a MB pressure tester that I use to check the spray pattern and pressure at which the injector opens, but it is not IMO, necessary to use this tester. If the above mentioned parts are not broken, the spray pattern is almost always correct. While I agree that the ideal situation is to have all the injectors open at the same pressure - which can be done by adjusting the thickness of the shims that sit behind the spring in each injector - but to do this, you WILL need the pressure tester.

MB itself gives you a range of pressures that your injectors should open at. If this range is met, I doubt that many people would notice the difference.

When you reassemble the injector, you must be sure that you really tighten the two sections of the body of the injector. The fuel is forced into the injector at very high pressure and if not really tight, it will leak out and wet the plug. The only other items are the compression washers which sit between the engine and the injector plugs. These are dime sized washers, and can be removed easily with a bent wire hook and should be replaced when re installing the plugs.

You don't have to buy the complete injector body. The nozzle and pin are sold separately if you find that you can't clean them.

You will need a deep socket wrench that fits the large nut on the injector (About 27mm or so). A long handled breaker bar to loosen and tighten the injectors. A bench vise to hold the injector while removing the assembly nut and an adjustable wrench for the smaller nut.

Remember to really torque the two sections of the injector body together and then the same when you reinstall the injector in the car.

It is helpful if as you disassemble the injector, you make a diagram or take digital pictures of where each of the few parts goes.

Jerry M. Keller