Repair or Buy New? Which Diesel Injectors Can Be Rebuilt
Most diesel injectors on the market today come from four manufacturers: Siemens, Bosch, Denso and Delphi. They have competitors, of course, but these four hold the bulk of the market, so many — if not most — cars run injectors from one of them. Why does that matter? Because not every manufacturer's fuel equipment can be repaired equally well. Here is how they compare:
- Bosch Common Rail. One of the most widespread injectors today, and it can be rebuilt without much trouble. The parts that fail most often are the multiplier (control valve), the valve seat and the stem. The stem itself cannot be reconditioned. During a rebuild the nozzle is either replaced or cleaned ultrasonically;
- Denso Common Rail. These Japanese injectors are fitted to European cars more and more often, and in quality they clearly outperform rivals in their price range. They are harder to repair: fewer spare parts are available, and only an experienced technician can strip and reassemble them — the injector has a lot of small components and needs special tools to take apart. That is why Denso injector repair is best left to a specialist workshop;
- Delphi Common Rail. The valve fails fairly often in these injectors, the nozzle a little less often. Both parts can sometimes be found in specialist stores, but usually have to be ordered online. After cleaning and replacing the worn parts, the owner effectively gets a new injector in the old body — at about half the price of a brand-new unit;
- Piezo injectors. Bosch and Siemens have the most experience with this newer generation of injectors, and piezo-crystal injectors are increasingly fitted to new models from European carmakers. The part that usually fails is the hydraulic accumulator; less often the valve breaks or the nozzle seizes. The repair itself is simple in principle ("strip, replace, reassemble"), but repair parts are rarely available.
