* COLD WEATHER FUEL CONCERNS *

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Common Diesel Fuel/Fuel Filter Problems in Winter

Diesel engine power loss during winter operation conditions is a common occurrence and a source of complaint. Unless there is a component failure within the engine, the problem can usually be traced back to gel formation in the fuel which restricts fuel flow through the fuel filter(s). Frequently, the fuel filter(s) are blamed for the problem when, in fact, the problem is caused by the effect of winter weather on diesel fuel.

Number 2 diesel fuel begins to cloud as the ambient temperatures drop toward the freeze point, 32 degrees F (0 degrees C). This clouding is the result of the wax (paraffin) in the fuel solidifying. As the temperatures drop below the freeze point, the paraffin molecules combine to become solids in the fuel which eventually become large enough to be stopped by the media within the fuel filter(s). This is commonly known as the "gel point" which generally occurs at approximately 10-15 degrees F (-9.5 degrees C) below the cloud point. The wax will then begin to form a restrictive coating on the filter media which results in a loss of engine power because fuel delivery is starved. The same process occurs when starting a cold engine with the ambient temperature below freezing. The fuel filter(s) media becomes almost instantly coated with a restrictive layer of wax. Usually, enough fuel can pass this layer to allow the engine to idle, but not enough fuel to allow the engine to attain operating RPM.

There are two commonly used methods to overcome the problem. One is to chemically treat the fuel with a diesel additive. The other is to install a fuel heater, typically an electric element on the filter.

1. Diesel fuel additives are available under numerous brands and with various formulations. When selecting an additive, it is important to determine whether or not it is formulated for winter conditions. Basically, diesel fuel additives designed for use in winter conditions depress or lower the gel point of the diesel fuel, thereby allowing it to flow through the fuel for the desired operating temperature range should be adhered to, as a deviation could yield either unsatisfactory results or harm the systems.

2. A diesel fuel heater can be installed in the fuel delivery system to prevent wax from accumulating on the fuel filter media. There are many different types with different points of installation, but they are all designed to maintain fuel temperature above the cloud point to the fuel filter(s).

Many operators of diesel powered equipment use both a fuel additive and a fuel heater.

Another problem experienced with diesel engines is water or condensation contamination of the fuel. Due to the fact that diesel fuel also acts as a lubricant for injector tips and nozzles and the fact that water does not provide lubrication, many operators install fuel filter water separators to provide additional protection. Water or condensation present in the fuel can further aggravate the problem of fuel gelling by further restricting fuel flow through the filters as well as corroding injector nozzles. However, it is important to remember that any fuel water separator must be drained periodically to remove any water which has collected. Failure to do so may cause an engine power loss, either as a result of the undue water build up within the filtering device thereby restricting fuel flow or by fuel flow velocity carrying water on through the system when the water level in the device becomes too high.

Therefore, depending on the severity of winter operating conditions, many operators may choose to protect their equipment by the use of fuel additives, fuel heaters and fuel water separators.

This article is reproduced with kind permission of the Field Support Unit, MSF Holland.