Bosch Guide: Potential Causes of Common Rail Injector Failures

If you are purchasing your own injectors, you should purchase from a reputable, OE manufacturer. If considering injectors from a non-OE endorsed manufacturer, be sure to ask the following questions to determine if the cost savings is worth the risk:

Do these injectors use new or reconditioned components?

It is preferred that the remanufactured injector use all new high-wear components vs. salvaged
components.

How are the remanufactured injectors tested?

You want injectors that are tested to exact OE test specifications and not reverse engineered
specifications.

What type of testing equipment is used?

  • It is preferable that their testing equipment is certified by the OEM.
  • It should be traceable back to the OE manufacturers testing.

Is there a warranty?

Many reputable manufacturers offer at least a one-year warranty.

Are the remanufactured/rebuilt injectors upgraded to meet new OE specs?

Are component improvements added to match changes made by the engine manufacturers?

Bosch is the world’s leading supplier of diesel fuel injection systems and is standard equipment on many diesel engines today. You can be confident when you install Bosch OE injectors, Bosch remanufactured injectors, or Bosch-authorized rebuilt injectors.


The common rail system is a major advancement in diesel technology. However, common rail engines are less forgiving of poor quality than older fuel injection technologies. What used to be acceptable in the past can cause the engine to malfunction and often result in a costly repair.

The key causes of injector failures are:

  • Fuel Contamination
  • Poor Fuel Filtration
  • Incorrect Installation
  • Non-OEM approved remanufactured products

Fuel Contamination

The majority of diesel engine problems stem from contaminated fuel. Common problems include corrosion from excessive water in the fuel, micro fine particles in the fuel and improper fuel storage, which is caused by water in the fuel.
There are two ways in which water can get into the fuel: through the delivery system and through the tank vent.

What Can I Do?

Solution: Always purchase fuel from a reputable service provider and use a proper fuel/water separator. Periodic inspection of the vehicle’s tank vent is also recommended.

Poor Fuel Filtration

A common problem with diesel injectors is erosion of the control valve. The heart of the common rail injector is the valve through which fuel passes at extremely high pressure. The passage opening is sealed using a pressurized ball that is only 1mm in size. A proper seal is critical for exact injector performance. Abrasive contaminants, released by inadequate filtration, can erode and damage the control valve and not allowing the ball to seal. This can lead to excessive smoke, starting or idling problems and potential engine failure.

What Can I Do?

Solution: To ensure exact performance within the designed service life of the injector, use only OE filters or filters having the same OE micron rating and follow the recommended OE filter change interval. Using anything less can cost you more in the long run.

Non-OEM Approved Remanufactured Products

Not all remanufactured injectors are the same. The quality of any remanufactured injector depends on the remanufacturing process and components. Some manufacturers sell refurbished/used injectors and market them as rebuilt. However, instead of being rebuilt, they are merely cleaned and polished, and the tips are not replaced. You might get a great deal on these non-OEM approved products, but you are taking a huge risk that these injectors may not be better than the one you are trying to replace.

What Can I Do?

Solution: Make sure your car is being serviced by a reputable shop and ask about the parts they use on your diesel engine to ensure they are from the OEM or from an authorized Bosch supplier.

Incorrect Installation

Missing sealing rings, incorrect tightening torque, incorrect cleaning of the nozzle can cause poor performance, misfiring , black smoke and check engine light (MIL) to come on.

What Can I Do?

Solution: Always follow the engine manufacturer’s maintenance procedures and have repair work done by a reputable shop.

Bosch’s remanufactured injectors follow the same fit, form, and function as OE injectors. Bosch remanufactured injectors include all OE updates, so they can often be superior to the OE injectors that they replace.
A-Bosch-Guide-to-Potential-Causes-of-Common-Rail-Injector-Failures_Sep_28_2016

Jimmy Finch

Dallas Branch Manager, M&D Distributors

Jimmy Finch has over 33 years of experience in Diesel Engine Sales, Service and Repair. His experience started early in life at Texas Fuel Injection Service (an early acquisition of M&D) as a job with a means to an end. Somewhere in that 33 years this job turned into a fulfilling career. He started in the injector clean up department and has held practically every position leading up to his current role as Branch Manager of the Dallas, Texas location.

In his spare time, Jimmy enjoys spending time with his wife of 24 years, Priscilla. They are currently getting ready to make their way into the empty-nesters stage of life. He also enjoys the occasional hunting trip with friends and family and chasing down potential customers by the names off their trucks.

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