Fuel filters capture unwanted contaminants from the fuel. Left unchecked, these contaminants can cause serious and expensive damage to many system components including pumps, lines and injectors, which can impact overall fleet operations and profitability.
Fuel contaminants originate from many sources. Most are external to the fuel system itself and come from the fuel that is delivered to the tank.
Fuel contaminants originate from many sources. Most are external to the fuel system itself and come from the fuel that is delivered to the tank.
The diagram below represents a fuel system with a primary and secondary fuel filter. Not all systems contain both a primary and a secondary fuel filter. Click on individual components to learn more about their function and construction.
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 fuel transfer pump delivers a vehicle’s fuel from the fuel tank to the engine. This pump may be electrically or mechanically driven and is pressurized at 20-60 PSI.
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.
The fuel injection pump pressurizes fuel before delivery to the fuel injectors and then the combustion chambers. The fuel system may be pressurized to 3000 psi and higher at the fuel injection pump.
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 fuel transfer pump delivers a vehicle’s fuel from the fuel tank to the engine. This pump may be electrically or mechanically driven and is pressurized at 20-60 PSI.
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.
The fuel injection pump pressurizes fuel before delivery to the fuel injectors and then the combustion chambers. The fuel system may be pressurized to 3000 psi and higher at the fuel injection pump.
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 systems, unlike lube systems, do not have the opportunity for bypass flow. Consequently, as flow through the fuel filter decreases, so does the performance of the fuel system and the engine.
Fuel filters will become restricted or plugged over their life — this is an expected result. A thorough investigation of the filter and the fuel source should be conducted anytime a fuel filter is suspected of delivering less than its expected life.
Filter manufacturers design fuel filters to provide the level of filtration protection specified or required by the OEM manufacturer. Substitution of a less efficient filter may prolong a filter's life before plugging occurs, but it will also allow contaminants to pass downstream, which will eventually impact the life of the other, more expensive fuel sytem components.
You should stress to your customers the importance of double-checking that the primary filter's element micron rating meets the engine manufacturer's specifications. In many cases a 30 micron or larger primary filter element can meet fleet PM intervals and offer reduced downtime due to premature secondary filter element plugging.
Water is potentially the most damaging of the expected contaminants. Moisture can reduce the lubricity properties of fuel and quickly damage fuel injectors and fuel pumps. In cold temperatures, water can freeze and stop the fuel flow.
Within limits, separators can remove both free water and emulsified water from fuel.
There are three common types of water separators, each with a different way of extracting water content from diesel fuel.
Uses a silicon-treated medium which limits the passage of water while allowing free fuel flow.
Uses gravity and low-flow rates to let water droplets gather together apart from the fuel.
Is made with media that contains a substance with a higher absorption affinity for water than for fuel.
Fuel enters the cylinder chamber where it is mixed with air, vaporized and burned to produce energy and send power into the vehicle’s component circulatory system.
The key to the on-highway heart health of your customer’s vehicles lies in the engine getting plenty of exercise as it racks up the miles, and to make sure it receives the cleanest diesel fuel possible.
As it comes from the refinery, diesel fuel is clean. Contaminants in diesel fuel are generally introduced in fuel storage systems through
Preventing problems and equipment damage associated with contaminated fuel is primarily the responsibility of the end user.
Download Luber-finer’s fuel system maintenance brochure to help communicate to your customers the importance of proper and timely replacement and servicing of fuel filters.
Preventing problems and equipment damage associated with contaminated fuel is primarily the responsibility of the end user.
Download Luber-finer’s fuel system maintenance brochure to help communicate to your customers the importance of proper and timely replacement and servicing of fuel filters.
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.
Water is the greatest concern 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.
Fungus and bacteria live in water and feed on the hydrocarbons found in fuel. Called “humbugs” for short, these 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.
Wax is desirable as a source of energy in diesel fuel, but control in cold weather conditions is needed. Wax crystals form as a result of cold temperature precipitation of paraffin. The cloud point of fuel must be at least minus 12 degrees Celsius (or 10° Farenheit) below the lowest outside temperature to prevent plugged filters due to wax formation.
Asphaltenes are components of asphalt that are generally insoluble and are generally present to some extent in all diesel fuel. These 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.
Sediment and other solids often get 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.
Fuel contaminants such as rust, dirt, scale and water can significantly compromise a vehicle’s performance capabilities if they’re allowed to reach the fuel system.
Premium fuel filtration is more important than ever before. Today’s demanding engines need high-performance protection to keep vital engine components such as fuel injectors clean and functioning at the optimum level.
These are the most noticeable indications that too many contaminants are reaching the fuel system or that a fuel filter needs to be changed:
A severely dirty or clogged fuel system can cause a vehicle to experience a decrease in power and acceleration.
Stuttering and jerking produced by the engine can occur when one or more cylinders misfires due to underperforming injectors.
Restrictions in the flow of fuel through the fuel system can cause a vehicle to experience hard starting or extended cranking.
Fuel cleanliness is extremely important to fuel injector performance. Tougher emissions regulations have led to engines with high-pressure fuel systems, which require extremely clean diesel fuel to deliver peak performance in these three areas:
Clean fuel moves smoothly through today’s high-pressure fuel injectors, which translates to more miles per gallon.
Eliminating even the smallest particles, down to 1 to 3 microns, can prevent significant damage to fuel pumps and injectors.
Fleets spend more time on the road when fuel system components reach or surpass their expected service intervals.
Is a fast-plugging fuel filter a bad filter?
Clean fuel is essential for efficient, full-power engine performance. Remember, newly refined fuel is clean. But between the time the fuel leaves the refinery and enters the engine’s fuel tanks, it can become contaminated if it is not stored, handled and transferred carefully.
Plugged filters will develop as the filter works to remove unwanted contaminants from the fuel system. 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, which will eventually impact the life of other, more expensive fuel system components.
Plugged filters will develop as the filter works to remove unwanted contaminants from the fuel system. 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 which will eventually impact the life of other, more expensive fuel system components.
Emissions regulations have forced diesel fuel to undergo changes that can have a severe impact on engine performance. From debris and particulates transported in fuel storage tanks to condensation and microbial growth in bio fuels, Luber-Finer’s heavy duty spin-on and cartridge fuel filters help maintain engine efficiency and performance.
Luber-finer’s standard media is designed to provide efficient and effective particulate removal and high capacities for reliable service life. Luber-finer’s standard media is designed to remove up to 99% of 25 micron particulate during normal use, and is the media that is present in all standard Luber-finer filters.
Luber-finer’s premium synthetic filter media is designed to provide enhanced efficiency and capacity, and is utilized in all XL fuel filters. Synthetic media removes 99.9% percent of all particulate 25 microns and larger.
Vehicles and fleets that operate in cold climates and frigid temperatures are subject to a special set of fuel and fuel system concerns related to winter operating conditions. There are three ways to address those concerns:
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 system for the desired operating temperature range.
Can be installed in the fuel delivery systems of the vehicles in your fleet to prevent wax from accumulating on the fuel filter media. They are designed to maintain fuel temperature above the cloud point determined by the lowest ambient temperature common to the area in which the equipment will be operating. Heating diesel fuel above the cloud point is the simplest and most reliable way to avoid plugged fuel filters. It is desirable to heat the diesel fuel as close to the filter element as possible, to re-liquefy wax and ice crystals.
Provide additional protection because diesel fuel acts as a lubricant for injector tips and nozzles and water does not provide lubrication. 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. It is important to remember that any fuel water separator must be drained periodically to remove any water which has collected.
Fuel filters, while similar to lube filters, have a particularly difficult task to perform. Physically, fuel filtration is no more difficult than lube filtration, however... managing customer expectations can be a challenge. They expect the fuel filter to provide adequate protection to sensitive fuel system components, such as injection pumps and unit injectors, and they also expect that the filter should last longer than is sometimes reasonable.
Fuel filter replacement intervals are calculated in much the same manner as oil and air filter replacements. Most customers have a predefined maintenance interval, that is typically calculated in miles driven (on-highway) or hours of runtime (off-highway). To calculate fuel filter consumption over a period of time, you can use the following equations:
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 engine, it's extremely important for sales representatives to understand the key benefits and considerable pain points related to fuel filtration.
Providing filter solutions to a customer’s fuel filtration challenges can be an effective way to drive sales, in both dollar value and volume. Due to the high likelihood that a fleet will rely on one supplier for its filter needs, fuel filter sales can help convert an entire fleet to Luber-finer® filters.
Filter Fact: Modern diesel fuel and bio-diesel blends can contain excess water and contaminants. A fast-plugging fuel filter is merely doing its job and is more of an indication of poor fuel quality.
