1. There are three types of fuel filter: diesel filter, gasoline filter and natural gas filter;
2. The function of the fuel filter is to prevent particles, water and impurities in the fuel, and to ensure that the precision parts of the fuel system are protected from wear and other damage;
3. The fuel filter is connected in series on the pipeline between the fuel pump and the fuel inlet of the throttle body. The function of the fuel filter is to remove the iron oxide, dust and other solid impurities contained in the fuel to prevent the fuel system from clogging, especially the fuel injection nozzle;

Fuel filter replacement  

1. First, loosen the clamping device at the junction of the oil circuit and the fuel filter, then remove the fuel filter from the oil circuit, and then plug the oil circuit with a plug to prevent fuel overflow.
2. Most fuel filters installed in the fuel path are marked with two arrows, one is the fuel inflow arrow, and the other is the fuel outflow arrow. The arrows are used to indicate the flow direction of the fuel when it passes through the fuel filter. So when we install the fuel filter, we must make the direction of the arrow point to the engine, that is, the oil flows to the engine.
3. In addition, it should be noted that the clamping device used in the oil circuit is specially designed, and the two parts are clamped tightly at the junction of the rubber hose and the fuel filter to achieve a sealing effect. Compared with the ordinary clamping device, this clamping device will not cut into the rubber hose, so it will not cause damage to the rubber hose. At the same time, the clamping device can withstand high oil pressure. Finally, we should also ensure that the rubber hose clamping device is installed in the correct position and clamps the joint according to the specified specifications.
4. If the car uses a maintenance-free fuel system and only uses a fuel filter built into the fuel tank. It is impossible to replace all fuel pumps, filters, and fuel output devices during the periodical preventive maintenance of automobiles. Even if the interval between regular preventive maintenance of the car is relatively long, it is impossible to do that because it is expensive. However, if there are signs that the engine performance is abnormal, or the fuel pressure of the fuel system is at a critical value, it is necessary to check or even replace the fuel filter placed inside the fuel tank.
5. After the maintenance of the fuel filter is completed, all the parts must be assembled and the fuel pump fuses must be reinstalled. Then, when the ignition system is not working, rotate the engine several times until the normal fuel pressure is established in the fuel system. At this time, check the fuel filter and oil circuit for leaks. If the inspection results show that everything is normal, start the engine and run it for a few minutes, and then re-check to make sure that there is no leakage.