Common Rail injectors - what are they for and how to know that they do not work

Common Rail (CR) technology conquered the world as early as 1997, when it debuted in Alfa Romeo car engines. In a very short time, other vehicle manufacturers began to use it. Compared to older technologies, Common Rail systems have significantly lower carbon emissions, quieter and quieter operation, higher efficiency and lower fuel consumption. As of 2010 (and Euro 5 emission standards), you will no longer find another injection system in passenger diesel cars.

Common Rail injectors are an integral part of the high pressure system. Their task is to dose / inject the fuel mixture from the injection pump into the combustion chamber of the individual cylinders under high pressure, in the best possible combustible state (= the smallest possible particles).

The Common Rail injection system allows high flexibility to adapt the fuel injection to the engine. This is possible thanks to the high injection pressures, which exceed 2,000 bar (200 MPa), as well as the possibility to adapt the injection pressure to the current operating state. Well-known manufacturers of common rail injection systems include Bosch, Siemens, Delphi, Denso and Zexel.

Proper common rail operation ensures perfect operation of the rail-mounted injectors. These components are responsible for accurate fuel metering into the cylinders. Unfortunately, any contamination of diesel can contribute to their damage. Common Rail systems use two variants of injectors according to the cell that moves the nozzle: electromagnetic and piezoelectric.

Electromagnetic (solenoid) injectors are the most widely used type of high-pressure fuel supply for diesel engines. They allow the division of functions to create high pressure and perform fuel injection. This makes the injection system more flexible and adaptable to the engine than traditional bag-driven systems.

The fuel in the tank is constantly under high pressure, so it is possible to adjust the injection by sending electrical impulses to the injectors. With new generation CR systems, it is possible to make several injections during a single engine duty cycle. This results in reduced fuel consumption, quieter engine operation and a lower content of hazardous substances in the exhaust gases.

Piezoelectric injectors enable more precise dosing of the amount of fuel injected and better fuel atomization in the combustion chamber of the engine. Their main advantage is the short activation time (approx. 0.1 ms). Piezoelectrically operated injectors have about four times higher switching speeds than electromagnetically operated injectors. Thanks to this, the gaps between the individual injections can be shortened and thus the injection process can be made more efficient. The advantage is also the saving of approximately 75% of moving masses on the nozzle needle. The only disadvantage is that piezo injectors are currently largely unrepairable, as their manufacturers do not supply the data and components needed for overhaul. We at Autonorm are able to repair / overhaul them thanks to hand-developed technologies and procedures. In this way, we help customers from all over Europe save the cost of purchasing new injectors, often by tens of percent. At the same time, they can use the same service life.

Causes of Common Rail injector damage

• natural wear and tear of respective components proportional to distance

• incorrect combustion pressure

• low fuel quality

• clogged DPF fuel filter

• fuel contamination in the fuel system (corrosion particles, dust, small metallic shards, water, and other unwanted liquids)

• incorrect installation of the fuel-dosing unit

• chiptuning

How to discern Common Rail injector malfunction

• decrease in engine power

• increased fuel consumption (due to injector flow)

• uneven engine idling (wrong injector calibration setting)

• increased engine noise

• difficult cold starts

• jerking or combustion outages while driving (incorrect dosing of the injector under load, the injector goes into the overflow)

• knocking sound at lower speeds (bad injector pre-injection)

• engine overheating

• sudden engine stop (common on piezoelectric injectors)

Note :The above symptoms may be caused by a failure of other engine systems. Therefore, we recommend verifying and checking the cause of the injection unit failure.

The best way to diagnose injectors is to measure with a multimeter, but with a basic knowledge of internal combustion engines, you can detect the problem on your own. The first signal of an injector failure is a sharp increase in fuel consumption. Other symptoms are audible hard engine operation, excessive vibration and large amounts of black or white smoke coming out of the exhaust.

Advantages of refurbished Common Rail injectors

• quality of a new part at a significantly lower price

• environmentally friendly

• Quality Certificate

How the injectors are being overhauled

1. disassembly of components from primary production

2. cleaning of all components with an ultrasonic cleaner

3. inspection of components under a microscope

4. unusable parts are discarded and replaced with new ones

5. functional components continue to be machined (grinding, sandblasting)

6. assembly of the injector by professional personnel using specialized tools from the manufacturer

7. coating anticorrosion treatment

8. output control (includes part of the output test report)

A DETAILED PROCEDURE FOR REPAIRING INJECTORS CAN BE FOUND HERE

Common Rail injector before and after overhaul