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Why do diesel engine common rail injectors fail? How to resolve these failures?

by MiaMia 09 Sep 2023


The fuel injector is an assembly composed of the fuel injector assembly and the fuel injector body, and the fuel injector refers to the fuel injector assembly. The fuel injector is the head of the fuel injector and the core part of the fuel injector. This article will introduce in detail the common fault causes and troubleshooting methods of diesel engine common rail injectors.


Fault 1. Nozzle clogged

Due to the solid residue particles mixed in the fuel, poor ignition leads to carbon deposition, which makes the nozzle semi-blocked. If the nozzle is blocked, the pressure of the oil supplied by the diesel pump will increase and the sound of knocking will come out.


Solution: The fuel entering the diesel pump must be strictly filtered to improve ignition and prevent nozzles from being clogged due to excessive carbon deposits.


Fault 2. Nozzle oil leakage

When the diesel pump is working, the airtight spherical surface of the needle oil circuit board will be impacted by the force of the needle valve, and the high-pressure fuel will continue to spray out from this point, and the spherical surface will gradually appear damaged or black spots, which will cause the diesel pump to leak oil. When the temperature of the diesel engine is low, the exhaust pipe emits white smoke, and when the temperature of the diesel engine rises, it becomes black smoke from the exhaust pipe.


Solution: Remove the nozzle, check whether the movement of the needle valve is flexible, and whether the airtightness of the seat surface is good, and then clean and match or replace a new nozzle pair.


Fault 3. Nozzle erosion and carbon deposition on the top

Nozzle corrosion is caused by thermal corrosion caused by sulfates in the exhaust pipe. The nozzles that are corroded are subjected to organic chemical corrosion because the metal surface is too cool.


Solution: Remove the nozzle, and use mechanical equipment or weak erosion to eliminate the carbon deposit on the nozzle. The elimination of carbon deposits inside the nozzle is very important, but it is necessary to maintain the airtight seating surface to avoid damage.If it is damaged, you need to replace the injector, you can refer to my other article:


Fault 4. The needle valve is stuck

Moisture or acidic and alkaline chemicals in the diesel engine will cause the needle valve to rust and get stuck. After the needle valve’s airtight spherical surface is damaged, the flammable gas of the master cylinder will also enter the coordination surface to produce carbon deposits, making the needle valve If the valve is stuck, the diesel pump will lose its pumping function, causing the cylinder to stop working.


Solution: Disassemble the diesel pump, remove the nozzle assembly, and remove the needle valve with special tools. If it is not easy to remove, put the nozzle assembly into the diesel engine and heat it for about 20 minutes before taking it out. When taking it, put a copper sheet on the tail end of the needle valve, pinch the tail end with needle-nose pliers, and pull it out while turning it. After unplugging, put it into the cleaning solution for cleaning, and then put it back in.


Fault 5. Poor atomization of injector

When the injection pressure is too low, the wear of the nozzle hole will cause carbon accumulation, and the end face of the spring will wear or the elasticity will decrease, which will cause the injector to open the hole in advance and close it later, resulting in the undesirable phenomenon of spray atomization.


Solution: Disassemble the syringe and clean it, overhaul and re-commission.


Fault 6. The spring is broken

In addition to the deformation caused by steel drops, the pressure regulating spring of the fuel injector often breaks, which has become one of the weak links of the fuel injector.


Solution: Use heat-resistant and fatigue-resistant materials to make the pressure-regulating spring work reliably. By reducing the power load of the spring, the spring can be immersed in the diesel oil in the injector body. When the injector is working, when the working rings of the spring contact each other, a hydraulic cushioning and some lubricating effect will be produced, thereby preventing the contact surface A pitted surface is formed which causes the spring to break.


Fault 7. The end face of the needle valve body is worn

Affected by the frequent reciprocating movement of the needle valve, the end face of the needle valve body gradually forms a pit, which increases the lift of the needle valve and affects the normal operation of the injector.


Solution: The needle valve body can be clamped on a grinding machine to grind and trim the end face, and then grind the grinding paste on the glass plate.


Fault 8. Abrasion on the surface of the needle valve and the guide rail of the needle valve hole

The frequent reciprocating movement of the needle valve in the needle valve hole, coupled with the intrusion of impurities in the diesel oil, will gradually wear the guide surface of the needle valve hole, increasing gaps or the appearance of pull marks, resulting in increased internal leakage of the injector and a pressure drop, the reduction of fuel injection quantity and the lag of fuel injection time lead to the difficulty of starting the diesel engine.


Solution: Replace the needle valve coupling.




The above content is an analysis of the possible faults and solutions of the common rail injector. What needs to be reminded is that there are many reasons for the failure of the fuel injector. When performing maintenance, professional testing equipment must be used.


If you know you have an injector problem with your vehicle or have questions about injector replacement kits, has the answers and products you need!


You can also view and purchase aftermarket injectors online catalog via the links below.



Related reading:


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