Section 4.4
Fuel Filtration
The most common cause of fuel system problems is failure to follow the manufacturer's recommended fuel filter change intervals. Preventing dirt and water from entering a precision fuel injection system is very important in obtaining the maximum life and performance of any diesel engine. If contaminants build up in the filter, it can significantly affect engine performance. The fuel delivery rate is reduced, making less fuel available for combustion. The fuel pump is forced to work harder to make the same volume of fuel. This subjects internal seals to abnormal conditions, which may lead to seal leakage. In extreme cases, air can be drawn in the system.
Filters make up an integral part of the fuel system. Proper filter selection and maintenance are important to satisfactory engine operation and service life. Filters, however, should be used to maintain a clean system, not to clean up a contaminated system.
Filter performance and test specifications vary between manufacturers. These specifications are general in nature and do not reflect the actual performance of genuine DDC Power Guard ® filters. The user is also cautioned when comparing micron ratings between filter makes. It is important to note that capacity and efficiency (micron) ratings should not be the only criteria on which to judge filter performance. Many other important factors, including media strength, resistance to impulse failures and burst strength, often differ greatly between filter makers and should enter into the filter selection process.
Finer filtration will generally provide increased engine service life, but many require shorter filter change intervals. Detroit Diesel specifies filter performance based on the optimum combination of filter micron rating, filter capacity and mechanical requirements.
Primary and Secondary fuel filters are essential to removing foreign matter from the fuel, before it enters the injectors. The first is usually a strainer that removes larger particles and the second is a filter, which removes micro-particles.
There is an optional filter called a Fuel Pro® filter that replaces the primary fuel filter. It consists of three major components: an aluminum fuel processor, filter element and clear cover. It is permanently mounted to the truck, typically in back of the cab where it can be easily seen. As fuel is drawn into the Fuel Pro filter processor, heavier dirt and water falls to the collection chamber in the bottom of the canister, where it can be purged through a manual drain valve. Fuel rises up out of the canister and passes through the 5-micron filter element and is discharged back into the fuel system. With the clear cover enclosing the filter element, it is easy for a driver or technician to see when the filter needs changing. There are two key advantages to this. First, unnecessary filter changes are eliminated, saving downtime and maintenance expense. Second, low power complaints related to restricted filters are quickly resolved.
By replacing the standard primary filter and changing the element only when necessary, the Fuel Pro can reduce filter usage by as much as 75%, as well as the hidden costs of downtime required to change them. Some fleets also request the optional thermostatically controlled heater, which warms fuel as it enters the processor and keeps fuel flowing for cold weather starts.
| Unit Fuel Injectors and Unit Pumps Technician's Guide - 7SE500 |
| Generated on 10-13-2008 |