Key fact: common rail diesel injectors are electronic.
F.A.Q. …find the answers to these questions and more in this article.
What are some of the differences between common rail and rotary diesel?
Are all common rail injectors the same?
What are the main components of common rail diesel injectors?
How are solenoid controlled injectors different to piezo injectors?
How can you visually tell a solenoid from a piezo injector?
Can a piezo injector be repaired?
CRD (common rail diesel) injectors are made by a variety of manufacturers.
Most widespread is Bosch. Bosch CRD injectors are solenoid-controlled or Piezo.
Common rail diesel injectors – part numbers
Bosch solenoid-controlled injectors have 10 digit part number 0445 110 xxx and Bosch piezo 10 digit part number 0445 115 xxx and 0445 116 xxx (mainly; there are of course some exceptions to this)
Delphi common rail injectors have part numbers like EJBR xxxxxx. The number is printed on a tag on the side of the injector. Usually requires injector removal from the cylinder head.
Denso part numbers are also printed on the injector (often necessary to remove) 10 digits e.g. 095000-xxxx. Often there is a model manufacturer’s number e.g. Toyota 23670-xxxxx
Delphi CRD injectors are fitted into a wide range of vehicles and are often of the piezo type
The use of Piezo crystals in the firing of the injection cycle allows for more precision control.
Piezo injectors also operate at higher opening pressures than the solenoid controlled type.
Solenoids are arguably more rugged but are slower to operate due to their electro-mechanical design.
Denso injectors are also often of the piezo type. This means they cannot easily be reconditioned. Denso do now have a rebuilding program for injectors but they remain amongst the pricier units to replace. They are electronically controlled by the ECU.
CRD injectors operate under the control of the ECU. This makes timing more precise along with finer control of fuel quantities. In addition fuel can be injected at different points in the combustion cycle.
They operate at high pressure. The development of diesel fuel injectors has seen them evolve from mechanical control (rotary diesel) to electronic control. Along with this precision has come much higher operating pressure. Rotary injectors opened at pressure around 120bar while modern CRD injectors can operate at 1600 bar and more. This higher pressure means that fuel can be more finely atomized; this in turn means more efficient combustion, lower emissions and quieter running. They inject fuel in a multi-stage process Common rail diesel injectors are multi-stage. This means they inject fuel in more than one pulse. This means fuel can be injected in time with the position of the piston to achieve maximum effieciency
The use of piezo crystals in design and manufacture of common rail diesel injectors means that if they fail they will need to be replaced with new; they cannot be reconditioned. This usually means that piezo replacement is more expensive.
Two methods can be used to identify CRD injectors. Firstly the visual appearance and secondly the part number.
Common rail diesel is usually direct injection. Fine atomization of fuel is made possible by nozzles with microscopic holes The nozzles fitted to CRD injectors are specific to that injector and its application. The holes in the nozzle are microscopic so blockage is possible. Attention to fuel cleanliness and filters will have an impact on the lifespan of the nozzle in the engine.