CRD Fuel Injector Failure Prevention

by Rob Gaskell, Jr.

The 6.6L Duramax, as well as the Isuzu 5.2L and 6.8L engines are a Common-Rail Diesel injection system, and all utilize similar Bosch and Denso fuel injectors. These injectors are prone to failure under certain situations, all of which are reasonably easy to avoid. These failures include conditions such as leaking fuel into the combustion chamber, leaking excess fuel to the fuel return line, and sticking, or misfiring, injectors.

The primary cause of fuel injector failure in a Duramax or Isuzu Common-Rail is a lack of fuel. Fuel in a diesel injection system provides lubrication to the injection pump and injectors. The fuel injectors on a Common-Rail system rely on high-precision components which can be easily damaged when they lack this lubrication. If the fuel injectors are damaged and leak fuel into the combustion chamber or the return line, this may cause an engine misfire and possibly a low fuel pressure condition, which can lead to damage to other fuel injectors.

Fuel shortages can be caused by clogged fuel filters, leaking fuel supply lines, or worn or malfunctioning fuel injection pumps. The fuel injection pump draws fuel from the tank, on most models, without the assistance of a lift pump. This suction causes the fuel in the supply line to be under a slight vacuum under normal conditions. This vacuum may cause leaking connections on the fuel supply lines to draw air in, and may not show signs of leaking fuel to the outside. This suction-method of drawing fuel from the tank also makes the fuel system more prone to problems related to clogged fuel filters. A less common cause of fuel shortages can be clogged fuel tank vents. As fuel is drawn from the tank, air must be allowed to enter the fuel tank through the vent. Partially clogged vents can cause an excessive vacuum in the fuel supply system, just as a clogged fuel filter will.

Fuel filters typically clog up over an extended period of time due to normal amounts of contamination in the fuel. However, poor fuel quality, the presence of water in the fuel, or contamination entering through damaged fuel caps or vents can cause these filters to clog very quickly. Contamination is particularly a problem on landscape and construction vehicles which are exposed to large amounts of dust and debris. Any time the water-in-fuel light comes on, the vehicle should be stopped immediately and the fuel filter drained. If the problem recurs, the fuel tank and supply lines should be examined for the presence of water or leaks which may be allowing water to enter. If there is water in the fuel tank, it may be time to reconsider where you are buying fuel.

Preventing Bosch and Denso fuel injector failures are actually very easy. Frequent fuel filter replacement is essential, and Fleet Service Northwest recommends the fuel filter on a Duramax be replaced every 6,000mi, or more frequently if the vehicle is used for towing or hauling loads. For an Isuzu Common-Rail, we recommend replacing the fuel filter when performing each Lube, Oil, and Filter service, which we recommend doing at 4,000mi intervals. Using quality fuels, and avoiding stations that may sell low volumes of diesel, which can cause contamination buildup in the station's storage tank, is another important way to avoid injector damage. Care should be taken when deciding to use biodiesel, and the use of homemade biofuels is not a good idea for any modern diesel engine.

Rob Gaskell, Jr.

Account Manager

Fleet Service Northwest

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