Signs of injectors issues
Starting problems / build up of rail pressure:
- Defect of high pressure sealing ring,
- wear of nozzle or valve piston guidance,
- defect/leakage of injectors valve seat / abrasive wear.
- Spread of injector to injector quantities too big,
- wear of nozzle seat or spray holes,
- fuel deposits harming the injector function.
- Mostly commonly caused by contamination (plugged orifices, or particle wear of valve seat).
Loss of power:
- High return flow,
- reduction of injection quantity,
- bad spray/atomization.
- Injection quantity of a single injector out of spec,
- injector solenoid has a too high resistance or a broken coil.
Poor fuel quality
The number 1 reason for injector wear, is fuel contamination from particles or water. The injectors have guidance clearances in the 1-3µm area. Every particle larger than that, will cause injector damage. Larger particles will destroy injectors at an alarmingly fast rate.
Water contamination will cause unrepairable corrosion damage. Corrosion spots can cause cracks by weakening the material and can harm the movement of injector internals.
The OEM Cummins fuel filters are not very good for keeping particles out of the system. They are designed to filter particles larger than 5µm. Updating the fuel filtration with 2/3µm filters, will extend the life of your entire injection system. An additional water separator will also help to avoid corrosion.
Excessive rail pressures
Injectors are designed to withstand specific maximum pressures. Bad tuning or common rail system failures, can increase the rail pressure. If you increase the pressure, you increase the risk that a part will crack. With every amplitude from low to high pressure, you are deforming injector parts. If you increase the amplitude from min to max pressure, the deformation will get larger. It is also better to increase idle pressure, if you increase maximum pressure, as the difference from min to max pressures will get smaller under operation, so there is less difference in parts deformation.
The solenoids function is to create the magnetic field to open the armature to finally inject fuel. The coil of the solenoid can have a short, crack or just an increase in resistance. If the resistance gets too high, you will have lower injection quantities or no injection.
If you test the resistance of a solenoid, measure the coil resistance itself, and also please measure the resistance of the isolation. To do that, simply measure between one of the studs and solenoid retaining nut. The isolation resistance should be infinite.
Normally it is tested with a higher voltage, but some failures can be found with a standard voltmeter.
Bad reman injectors
HPCR Injectors are complicated. If the rebuilder does not know the whole system/functionality of a CR injector or what injector adjustment tolerance will influence what function of the injector, he will not be able to rebuild them correctly. We get a lot of cores back from our customers. We have determined that very often the reason for a failed injector set, was a single injector, that was already rebuilt from a third party.
You get what you pay for. If it is too cheap to be true, it is too cheap to be true. We have never seen a Chinese injector copy work properly. Side note: We also do not accept them as cores, as we only rebuild original Bosch injectors for our remanufactured line.