The fuel filter is to reduce the flow of contaminated fuel to the injection elements. It is particularly important for modern petrol injection systems, and common rail systems used in diesel engines, since in modern injection systems components fitting is in microns.
Fuels are clean, so what's the point?
In theory, fuels offered at gas stations are of good quality and if you are refueling at large, international gas stations, you may rest assured that the fuel is not contaminated. However, taking in fuel, in which there are particles is not the only problem. The current injection systems that deliver fuel to the strip under pressure of up to 2500 atm (common rail system in Audi), and from there through microscopic holes in the injector/spray, inject it into the cylinder must be more secure.
Currently it is not the particles of sand, but particles of a few thousandths of a millimeter that can decalibrate the injector holes and destroy the injection system. This, in turn, is associated with huge costs that will fall on the user of the car. Hence, if you want to sleep peacefully, take care of the fuel filter.
Owners of older cars must also remember that contaminated fuel may come from... their own car. Research on filters carried out in one of the companies involved in the production of these devices have found such components as: rust, water, organic matter and minerals (dust, sand). These impurities appear in the fuel due to damage to fuel tanks (both at the gas station and in the car), and due to the car's operating conditions (paved road, off-road drive, unpaved road, driving through the construction area).
All these problems may be neutralized by the fuel filter.
The fuel filter, which is plugged into the fuel line and is located in the engine compartment, should be replaced as per the manual. However, in the case of cars that are more than five years old, replacing the filter every year is recommended regardless of mileage (this results from the possibility of particles that pollute fuel embedding in the fuel tank)
Every filter is subject to wear, and this results in reduced flow of fuel. Filter contamination involves reducing the clearance of the perforation holes in the membrane, whereby the flow of fuel is hindered, and this prevents the required amount of fuel from reaching the injection system. This may result in:
- increase in fuel consumption
- reduced engine power
- disruption or interruption of fuel supply
- deterioration of the fuel pump efficiency, including the possibility of scoring
- in extreme cases, damage to the power supply.
In view of the fact that diesel is more contaminated, and the injection pressure is significantly higher compared to gasoline, this guide is focused mainly on filters for diesel cars.
It is therefore worth considering how unwanted particles find their way into the fuel.
Water in the fuel
Water in diesel fuel results from changes in temperature (dew point and condensation), and its main cause is leaving an empty space in the tank. If water gets into the injection system, it can cause corrosion damage. Hence, filtration devices offered by Master-Sport thoroughly separate the water from the fuel. They cause accumulation of water molecules in the pores of the filter, where pure water is precipitated. With density greater than diesel, it falls to the bottom of the settling tank, where it can be drained.
It must be remembered, however, that in the winter, a car left on the cold should never (!!!) have less fuel than below half the tank
One of the components of diesel fuel is paraffin. Its physical properties make it transform into crystals at 0°C, and these are the most common cause of filter clogging in the winter. Therefore, diesel fuel has to be appropriately prepared to operate at lower temperatures. To this end, suitable additives are added already at the refinery, which limit the growth of crystals, so that they are small enough to pass through the pores of the filter.
The once popular method of "refining" diesel oil by adding small amounts of gasoline and kerosene became discouraged and, in modern injection systems, even unacceptable.
The "refining agents" currently used by drivers can be depressants. Their task - once mixed with fuel - is to prevent separation of paraffin. They are useful primarily when there is a severe frost or when we carry summer diesel fuel in the tank.
It is also important that they only prevent the formation of new crystals, but do not dissolve those already present. Hence pouring in the depressant after the onset of paraffin crystallization in bad fuel is pointless.
It is the crystallization of paraffin that is the reason why you must replace the diesel filter before each winter. Dirty pores of the membrane filter reduce their diameter. Moreover, in the winter, paraffin crystals clog them and it may happen that a speck of paraffin flows through the new filter system, but a dirty one proves to be too small and the fuel will not flow.
At the end it is worth mentioning about replacing the filter
Typically, the replacement may be performed by anyone, without requiring any experience in workshop engineering. In order to replace it, you only need to tighten the rubber ends of the hoses (so that the fuel doesn't flow out), remove the bands from the hoses, remove the hoses from the spigots, then pull out the old filter, insert the new one and properly retighten the hoses exactly as they were installed in the previous filter. It is important that the filter is secured in accordance with the indicated direction of fuel flow.
When you mount a new filter, it should be filled with fuel. To this end, in cars with petrol engine with fuel injection and diesel common rail systems, before starting the drive unit, you should repeatedly turn the ignition key in the ignition position, so that the fuel pump (working after ignition) fills the system at the appropriate pressure.
In older cars with diesel engines, there is a pump that you should use to vent the fuel system. The pump is a rubber bulge on the hoses or a button in the filter housing, which should be pressed until the entire system fills up.
It should also be remembered that in the case of diesel engines, replacing the filter should be done before each winter, since this is the period when the fuel filter accumulates the most water, heavy oil fractions, as well as paraffin. Driving another winter with a contaminated filter may result in problems with start-up and, in worst cases, the need for costly repairs of the engine accessories.