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All About Common Rail Injectors

Updated: Sep 19, 2022



Common Rail injectors of today can perform multiple injections in a single combustion cycle in a diesel fuel engine. They also inject fuel into the engine at higher pressures (up to 30,000psi) through clearances as small as 1 micron. This has significant advantages, including lower emissions, better fuel economy, and better drivability. However, it also makes them more vulnerable to wear and tear. We will be discussing the most common reasons for injector failure and the symptoms.

Why Do Common Rail Injectors Fail?

Common Rail injectors are built to last but advances in injection technology have made them more susceptible to damage.

  • Particle contamination: Even the smallest particles can cause serious damage. Tolerances are only a fraction of the width of a human's hair. Ineffective filtration can lead to tiny particles eroding the control valve and ball. This causes a poor seal between them. This can lead to a change in the fuel spray pattern and, consequently, the timing, distribution, and quantity of fuel injected.

  • Fuel contamination: This is another common reason for Common Rail injector failure. Water can get into the fuel and react with the chemicals to cause corrosion and decrease lubrication. This can lead to premature wear on both the high-pressure fuel pump and injectors.

  • The build-up of deposits: Fuel left in an injector after the engine has been shut down will be effectively 'cooked' by residual heat. This creates carbon deposits also known as "coking". These deposits can build up around the injector's internal components and the nozzle tip, making it stick. This can also disrupt the timing and quantity of injections.

  • Poor installation: Incorrect installation can lead to premature failure. A missing or improperly seated nozzle washer can allow combustion residue to leak through the washer. Seal rings can also easily slip out of their grooves. These problems may not seem serious, but they can lead to more serious issues such as poor injector performance and reduced fuel economy.

Common Rail Injector Problems

Faulty fuel injectors can cause fuel to be ejected from the combustion chamber. It could even stop it from happening altogether. It can have a variety of symptoms, including affecting vehicle performance.

  • Check engine lamp: If the engine isn't performing as it should, this can cause the engine management light (to come on) to turn on. To confirm the fault code, a diagnostic scan tool is required.

  • Rough idle If fuel delivery is restricted the RPM at idle will drop, resulting in rough idle. The car will eventually stop if this is too low.

  • Engine knock - When the fuel mixture is incorrect, such as an air-fuel mixture, it can cause premature ignitions. These can be heard by the engine sounding a knock or ping.

  • Engine surge A faulty injector could also cause an engine surge by supplying too much fuel to the combustion chamber. Engine revs will continue changing under constant load and throttle if this happens.

  • Engine misfire: A disrupted fuel supply can cause the engine's combustion chambers to not produce enough power, which could lead to misfiring.

  • Fuel leakage If diesel is found near the injector's exterior, it could be a sign that the injector has been damaged. Alternately, the seal could have broken.

  • Low fuel economy The ECU will compensate for any defective injectors by allowing for over-fuelling. This causes the engines to run too rich and use more fuel than it needs.

  • More emissions A bad injector could also cause incomplete combustion of diesel fuel and, as such, increase emissions in diesel vehicles.

How to Care for Or Look After Common Rail Injectors

A simple maintenance guide is another way to keep customers satisfied. Regular TLC, just like other parts, will keep your injectors in top shape for longer.

  • Regularly inspect injectors - this should happen every 20,000 miles, but it may be sooner if you make shorter trips.

  • To keep your engine parts free from deposits, use premium quality fuel with additional detergents

  • To maintain the condition and health of your fuel injection system, you should periodically add a fuel system cleaner.

  • To keep your engine running at its best, make sure to change the oil often. It can slowly start to lose its ability to clean and cool the engine.

  • Regularly change the fuel, oil, and air filters. Filters that are dirty or blocked can allow contaminants to enter the engine. This can cause damage to key components and negatively impact engine performance.

  • Take into account your driving style. Hard driving and shorter start-stop times will cause more strain on the fuel injection system.

CRD Specialists are your local Diesel Fuel Injection & Pump Mechanic Services Australia Wide. We offer quality and experienced fuel injection cleaning, repairs, rebuild, parts and service. Brisbane, Sydney, Canberra, Melbourne, Hobart, Adelaide, Perth, Darwin and all cities, towns and areas in between.

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