Diesel Fuel Injector Issues

As fuel injection technology has evolved over the years, so have the problems associated with injector fouling and plugging. In the past, deposits from unburned fuel on injector tips and plugged tiny injector nozzle holes would build up over time. These buildups disrupt fuel’s spray pattern and atomization, robbing engines of the proper amount of fuel delivered and reducing power. A slow progression of these buildups made performance being lost nearly undetectable. A loss of power is accompanied with a decrease in fuel economy and an increase in emissions. At the time, diesel fuel detergents were developed to clean up these fuel injector deposits and restore engines to their optimal performance.

Originally, fuel was pressurized by a distributor pump or via individual pumps to fuel injectors in each cylinder. Pressure was maintained around 1800 psi. The current evolution of the fuel distribution system is the common rail fuel injection system. These fuel injection systems develop up to 30,000 psi pressure.

To meet increased diesel emission requirements, injector delivery systems have been engineered to deliver multiple injections per cycle. The precise metering of fuel under very high pressure requires tolerances that have become extremely tight within the injector, a few microns, and leading to injectors that are very sensitive to particulate contamination. (A human hair is 17-181 microns in diameter.) The result is that additional injector problems can come from internal injector deposits that can cause sticking. An injector that becomes stuck in the open position could result in an engine that was running fine in the morning to possible engine failure from excessive diesel fuel in the cylinder.

One of the new causes identified for internal sticking of injectors is sodium salts of alkenyl succinic acids. These salts are insoluble in diesel fuel and can exist in very fine particles that pass through small micron fuel filters and to the injectors. Sodium can enter the diesel fuel distribution system in many ways including refinery salt dryers, sea water used as ship ballast, and tank water bottoms. Alkenyl succinic acids are commonly used as pipeline corrosion inhibitors. It has been shown that both need to be present to cause the sticking issues.