Siemens Piezo Injector Testing – Misfire caused by bad spray pattern Posted by

This is a video of our ASNU Injector Diagnostics Programme in action with some Siemens Piezo injectors.

The customer complained of a misfire registering on the system – according to the customer it had something like 600 registered.

These had been checked on a high pressure system and passed as OK. The customer did tell the workshop what the problem was and they gave them a clean bill of health after servicing and they came back as OK.

The customer fitted them back to the engine, entered the injector codes, cleared the fuel trim register and fault codes and sent the car out. A few days later the customer returned complaining of the same problem and sure enough the system registered misfires.

The customer (in Europe) sent them to us for testing and we examined them thoroughly and there was no apparent problem, but when we rotated the number 1 injector, we saw the spray pattern changing with a split and a slight jetting as it split.

Given that these injector can operate at a 60:1 Air Fuel Ratio, even this slight difference will make a big difference in the combustion chamber.

As these were tested at high pressure and you cannot rotate the injectors at that pressure (very dangerous) it’s possible that the “misfire” was not visible or that it is not easy to see at high pressure because of the high atomisation.

We ultrasonically cleaned the injector again but the “misfire” remained; our recommendation was that the injector was replaced.

The injector was replaced and the problem no longer existed.

When testing GDI Injectors on an AFTERMARKET vehicle, understanding what is important about the injector’s performance and its relation to the correct running and performance of the cars engine, for those without experience and education on GDI injectors always believe you must test at systems pressure.

ASNU have been testing and servicing GDI injectors since 1998. Having tested and serviced 1000’s of GDI Injectors from all the various injector manufacturers, we believe that our knowledge and experience in this market in over 60 countries and over 10,000 users worldwide gives us the authority to educate the inexperienced in the process of ASNU Injector Diagnostics.