Diesel fuel injectors these days are incredibly complex, and that means remanufactured fuel injectors need extra scrutiny. Bosch, which supplies new and remanufactured diesel fuel injectors, recently tested remanufactured and rebuilt common rail injectors and found 70% failed the test.

The company tested numerous remanufactured or rebuilt common rail diesel fuel injectors purchased from several replacement suppliers. It used a Bosch EPS-815 test bench with Bosch patented Shot to Shot (SST) functionality including original equipment manufacturer calibration values. The focus was to evaluate injector performance as well as the impact these remanufactured or rebuilt injectors would have on the engine.

“Alarmingly, we found that 70% failed our comprehensive testing and would present significant engine performance issues if installed in a diesel common rail system,” says Ross Sandercock, director of diesel products for Bosch, Automotive Aftermarket.

Vehicle performance concerns that the Bosch team found in unauthorized injectors included:

• No start

• Internal and external leaks

• Rough idle

• White and black smoke

• Low power

If those questionable diesel injectors were installed, Sandercock says, "it could result in having to redo the whole job – removing the defective common rail injector and re-installing a new injector, which could take up to eight hours. It only takes one faulty injector to negatively impact engine performance. Hardly worth a few dollars saved in injector costs."

Today’s diesel fuel injectors are controlled by the vehicle’s ECU, and are designed to cycle up to eight times per combustion event when injecting fuel into the engine.

“Vehicles as of 2007 require sophisticated exhaust systems for controlling emissions. Faulty injectors could cause serious damage to the exhaust system resulting in higher repair costs,” Sandercock says.

Traditionally, legacy injectors had one injection per power stroke, explains Omar Cueto, president of L&J Diesel Service Inc. in Jacksonville, Fla., home of the Dieselogic brand. "The magic about common rail is it can inject multiple times in one power stroke. This allows the opportunity for reduction of emissions and noise with increased efficiency, power and torque."

Some aftermarket rebuilders take shortcuts, says Bosch's Sandercock.

“To produce and market fuel injectors at low prices, some remanufacturers salvage parts which are outside of tolerance, rework sealing surfaces, or add chrome to worn parts which eventually wears off. All this changes the geometry of the injector itself, leaving it unable to function as intended in the engine for which it was designed,” Sandercock says.

Another issue of lower performance of remanufactured common rail injectors is directly related to the nozzles supplied from different countries that have less experience with electric discharge machining, special coatings, extrusion treatment of the nozzle holes and other factors, Cueto says.

The calibration challenge

Perhaps an even bigger problem, Cueto contends, is the calibration of the injectors.

"To be honest, the better part of the aftermarket has been botching common rail injectors pretty badly, because the  conventional test equipment available does not allow the resolution  required for this advanced type of fuel injection system," he says. “Not being able to acurately measure a pre-injection or multiple injections in one power stroke can only be described as total blindness.”

On top of that, aftermarket remanufacturers, he says, don't have access to OEM internal calibrations, which makes it very difficult to calibrate such parameters as discharge volume, start of injection, end of injection, electric supply current profile and standard deviations.

Even OEMs, he contends, do not provide their own certified remanufacturers with the same level of instrumentation used in their own remanufacturing.

While Cueto agrees with Bosch's message to use caution when choosing remanufactured injectors, he also offers a different perspective on the “conventional” option. L&J Diesel Service Inc., through its Dieselogic brand, manufactures a test bench (the NEO) that uses patented fiber optic technology. He adds that when all wear parts are replaced and properly calibrated, the injector should perform as intended, regardless of the remanufacturing facility.

"Our research and development team has devoted nearly a decade to reverse engineering these internal calibrations to offer the aftermarket a choice, thus offering a resolution as good or better than the OEM, which is the true definition of a remanufactured product," Cueto says.

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