Fuel is the lifeblood that runs through the heart – the engine – of any heavy duty vehicle. When fuel enters the cylinder chamber, it is mixed with air, vaporized and burned to produce energy and send power into the rest of the vehicle’s circulatory system.
The key to the on-highway heart health of vehicles lies in the engines getting plenty of exercise as they rack up miles, as well as making sure engines receive the cleanest diesel fuel possible.
That’s where fuel filtration comes in. Left unchecked, fuel contaminants can negatively impact overall fleet operations and profitability. Most of these contaminants are external to the fuel system itself and come from the fuel that is delivered to the fuel tank.
Fuel filters capture these contaminants before they can cause significant and expensive damage to many vital fuel system components.
Primary Components
The primary components of a vehicle’s fuel system are:
- Fuel transfer pump – The fuel transfer pump delivers a vehicle’s fuel from the fuel tank to the engine through the fuel lines. This pump may be electrically or mechanically driven and is pressurized at 20 to 60 psi.
- Primary/secondary fuel filters – These remove contaminants from the fuel.
The primary fuel filter usually mounts before the fuel pump on the suction side. It is designed to protect the fuel pump from contaminants and abrasives.
The secondary fuel filter is usually mounted after the fuel transfer pump on the pressure side. It is designed to remove fine abrasives that can block and damage fuel injectors.
Note: Some fuel systems contain only a primary fuel filter, which protects both the pump and the injectors. - Fuel injection pump – The fuel injection pump pressurizes fuel before delivery to the fuel injectors. The fuel system may be pressurized to 3,000 psi and higher at the fuel injection pump.
- Fuel injectors – These deliver fuel to the combustion chambers, which produce energy for the vehicle’s drivetrain.
The Importance of Clean Fuel
The primary reason clean fuel is so important is fuel injector performance. Tougher emissions regulations have led to engines with high-pressure fuel systems. The internal components of modern fuel injectors are often extremely small and very susceptible to wear or sticking due to particles and other kinds of contamination.
Unclean fuel can decrease the life of these components and may even cause malfunctions that could result in severe damage to other parts of a vehicle’s fuel system and engine.
That’s why premium fuel filtration is a must. When injectors are functioning at the optimum level and delivering clean diesel fuel to the engine, the result is peak performance in these three areas:
- Improved fuel economy – Clean fuel moves smoothly through today’s high-pressure fuel injectors, which translates to more miles per gallon.
- Proper fuel system function – Eliminating even the smallest particles, down to 1 to 3 microns, can prevent significant damage to fuel pumps and injectors.
- Reduced downtime – Fleets spend more time on the road when fuel system components reach or surpass their expected service intervals.
Fuel Filters
Fuel filters naturally build resistance to the flow of fuel as they go about their job of removing unwanted contaminants from the fuel system. Fuel filters will become restricted or plugged over the course of their lives. This is an expected result.
Service personnel should conduct a thorough investigation of the filter and the fuel source anytime a fuel filter is suspected of delivering less than its expected life.
However, in no case should a more “open” filter be substituted to fix a perceived problem with premature plugging. Substitution of a more “open” filter may prolong a filter’s life before plugging occurs, but it will also allow unwanted contaminants to pass downstream. That will eventually impact the life of other, more expensive fuel system components.
Common Fuel Contaminants
The most common fuel contaminants are:
1. Water. Water is the greatest concern to fleets and service personnel because it is the most common form of contaminant. Water may be introduced into the fuel supply during fueling when warm, moisture-laden air condenses on the cold metal walls of fuel storage tanks, or from poor housekeeping practices.
Water can introduce rust into the fuel system, damage fuel injectors or reduce the lubricity of the fuel, which can cause seizure of close-tolerance assemblies such as plungers.
2. Fungus and bacteria. These organisms live in water and feed on the hydrocarbons found in fuel. Called “humbugs” for short, the active and multiplying colonies will spread throughout a fuel system and quickly plug a fuel filter. The result will be a slime coating over the surface of the fuel filter’s media, dramatically reducing the service life of the filter.
3. Wax. Wax is desirable as a source of energy in diesel fuel, but it can cause problems in cold weather conditions. Wax crystals form as a result of cold temperature precipitation of paraffin.
The cloud point of fuel must be at least minus 10 degrees Fahrenheit below the lowest outside temperature to prevent plugged filters due to wax formation.
4. Asphaltenes. These are components of asphalt that are generally insoluble and are generally present to some extent in all diesel fuel. The black, tarry substances are hard and brittle, and are made up of long molecules.
Fuel with a high percentage of asphaltenes will drastically shorten the life of a fuel filter.
5. Sediment and other solids. Various tiny materials often make their way into fuel tanks and cause problems. Most sediment can be removed by settling or filtration.
Fuel filters designed for specific applications will remove these harmful contaminants before they cause further system wear and damage.
Warning Signs of a Fuel System Problem
These are the most noticeable indications that too many contaminants are reaching the fuel system, or that a fuel filter needs to be changed:
- Loss of power – A severely dirty or clogged fuel system can cause a vehicle to experience a decrease in power and acceleration.
- Hesitation – Stuttering and jerking produced by the engine can occur when one or more cylinders misfire due to damaged or underperforming injectors.
- Hard starts – Restrictions in the flow of fuel through the fuel system can cause a vehicle to experience hard starting or extended cranking.
Conclusion
While often not as top-of-mind as oil and air filters, fuel filters comprise a quarter of the heavy duty filtration market. Because of the severe consequences contaminated fuel can have on a vehicle’s fuel system and engine, it's extremely important for fleets and service personnel to understand the key benefits of a properly maintained fuel system, and how fuel filtration contributes to fuel system performance.
Zafar Hussain is a senior product engineer at Luber-finer (www.Luber-finer.com), one of the world’s most trusted filter brands. He has worked in the filtration industry since 2002 and has multiple patents under his name, including Luber-finer’s Heavy Duty Time Release Technology (TRT) Oil Filter. For more than 75 years, Lube-finer has been providing filtration excellence for heavy duty on-highway vehicles, vocational and off-road equipment.Â
