Common Rail Diesel Technology
Due to the way the system is electronically monitored and controlled, common rail fuel injection improves the timing and quantity of fuel delivery into the combustion chamber. At present, common rail systems are the only way that manufacturers can comply with European Union emissions legislation for diesel engines.
Common rail fuel injectors have had to evolve in order to keep pace with the increasingly strict demands of EU legislation. One of the ways to enable the engine to deliver reduced emissions has been to increase the frequency of fuel injection, from just 3 injections per cylinder stroke (which was the norm 15 years ago) to up to 7 injections per stroke (system dependant).
Common rail injection operates at significantly higher pressures compared to mechanical systems, helping the system to give better fuel atomisation. With pressure levels within the common rail system running so high (2,000+ bar, system dependent) extremely fine tolerances are needed throughout the system. In order to achieve this, the internal components of the injectors must be very precise. For example, one constituent within a solenoid injector, called a “needle lift spring shim”, has a thickness range from 1 to 2mm. Within that range there are 52 thickness options, each 0.02mm different from the next. Incorrect selection or assembly will prevent the correct operation of that injector, compromising the system operation.
Such strict tolerances mean that even the slightest defect in component design, or compromise in quality, can cause a terminal failure within the fuel system. This is true for both original and replacement parts.
Common injector faults
Premature injector failure is usually the result of one of the following common problems:
• Contamination – dirt and debris enters the system through uncapped lines/connections
• Water damage – fuel filter not changed at specified intervals
• Mis-fuelling – diesel lubricates the injector’s internal components, more viscous types of fuel can cause rapid wear and failure; while petrol will not lubricate at all
Injector removal issues
Remember: old core must be suitable for remanufacture in order to gain the credit; parts that have been excessively damaged during removal are unsuitable for a refund.
Removing injectors from a vehicle without damaging them requires dedicated injector removal tools. These tools are readily available in the aftermarket.
For more information on whether or not a part is acceptable for return please visit the Carwood section in the ‘Core Acceptance Criteria’ section of Part Info.