Why Do Diesel Fuel Injectors Fail?
Diesel fuel injectors have a critical role within the diesel engine, delivering fuel to the combustion chambers in specific patterns and at specific pressures. When injectors start to fail, drivers usually notice one or more common symptoms: difficulty starting, uneven idling, misfires, fuel odor, dirty exhaust and/or decreased efficiency.
Fuel injector issues often start at around 100,000 miles, although driving habits and engine model can cause this to vary quite a lot. When diesel fuel injectors do fail, the cause is usually one of the following.
External Injector Deposits Caused By Unburnt Fuel
The most common diesel fuel injector problem has historically been external injector deposits that develop from unburnt fuel. Also known as “coking deposits,” these deposits build up as unburnt fuel collects on the injector nozzle. Once the deposits start to block the injector nozzle’s holes, they can disrupt spray patterns.
External injector deposits usually don’t cause all-out failure, but they can have a significant negative effect on fuel efficiency and power. Deposits may be cleared out with a detergent, or the injector may have to be cleaned by a diesel technician.
Internal Injector Deposits Caused By Unburnt Fuel
Internal injector deposits develop when unburnt fuel collects on the interior components (as opposed to the nozzle) of a diesel fuel injector.
Internal deposits can form on almost any diesel engine, but they mainly cause noticeable problems on modern high-pressure common rail (HPCR) diesel engines. These engines have tighter tolerances in order to meet stricter emissions standards, and deposits are therefore more likely to cause problems. A diesel service center that has the right bench can service common rail injectors that have these deposits.
Abrasions Cause By Impurities
Despite diesel processors’ best efforts, all diesel fuel has at least some impurities. Most impurities are either small enough to pass through an engine without issue or large enough to be caught by the fuel system’s filters. In some cases, though, impurities can make their way to an injector and cause problems.
When impurities reach an injector, they can cause abrasions. Abrasions most notably can impact fuel spray patterns, thus creating decreased performance. This is a potential problem in any diesel engine, and it typically requires a diesel technician’s knowledge to assess the level of damage and suggest the right repair.
Excessive Wear Caused By Modern Diesel Fuel
Diesel fuel changed in 2006, when the United States mandated that all diesel fuels reduce their sulfur content. Diesel that was made before this date often contained a lot of sulfur, because the sulfur acted as a lubricant for engines. Today’s ultra low sulfur diesel isn’t as lubricating.
While many diesel processors add other lubricants to their fuel, not all of the diesel sold today is as lubricating as older fuels used to be. This can lead to excessive wear on diesel fuel injectors, which can cause premature failure. Worn injectors often have to be replaced.