As we all know, the engine is the “heart” of a car. If there is a problem with the engine, the car often has to lie down! Therefore, the maintenance of the engine can not be the same as that of soaking medlar in middle age. It needs to be maintained regularly according to the maintenance cycle in the user’s manual corresponding to the engine, which can not only avoid many unnecessary troubles, but also prolong the service life of the engine and make you drive more smoothly.
Composition and working principle of fuel system
Take the cursor9 engine as an example. As the engine rotates, the high-pressure oil pump rotates. The gear pump at the front end of the high-pressure oil pump begins to suck the fuel from the fuel tank into the fuel system. The fuel enters the ECU after two coarse filters on the frame girder, and then cools the ECU to maintain the stable working temperature of the electronic control components. Then it enters the gear pump, enters the filter on the engine cylinder head after passing through the gear pump, and then enters the high-pressure oil pump for pressurization, The pressure of the high-pressure oil pump can reach 300-1800 atmospheres after pressurization. After pressurization, the fuel enters the common rail pipe. The fuel injector injects the fuel in the common rail pipe that reaches the set pressure into the cylinder for combustion according to the command of ECU. (the working principle of cursor11 & 13 engine is the same as above, but the fuel will not pass through ECU.)
Fuel system selection
Before choosing the fuel of diesel engine, we need to understand two concepts, freezing point and cloud point. The cloud point is the temperature at which the diesel begins to crystallize, and the freezing point is the temperature at which the fluidity of diesel is affected.
The domestic diesel oil label is based on the freezing point. For example, the freezing point of – 35 diesel oil is minus 35 ℃. Because the cloud point of diesel oil is higher than the freezing point by 6 ℃, the paraffin crystal of – 35 diesel oil will appear at minus 29 ℃. At this time, the paraffin crystal will block the filter element, resulting in the powerlessness of the vehicle. Therefore, we should pay attention to its cloud point when selecting diesel oil.
Key point 1: select diesel whose grade is at least 6 ℃ lower than the ambient temperature.
In addition to the cloud point of fuel, we should also pay attention to the cleanliness of fuel. The suspended particulate matter and floating water in fuel oil will directly affect the performance, reliability, service life and emission of diesel engine fuel system.
The particle suspension will pollute and block the internal holes of the fuel injection system, and the working pressure of the diesel injection system is very high. Under such high pressure, the dust and rust particles in the fuel will become abrasive materials and quickly destroy the high-pressure pump components and fuel injectors. In addition to combustion, the fuel will also cool and lubricate some moving parts of the fuel system, but the water in the diesel will seriously reduce its lubrication performance, resulting in rapid wear and corrosion of high-pressure parts and endangering the engine.
Key point 2: choose transparent liquid without suspended particulate matter and floating water, and high-quality vehicle diesel without peculiar smell.
Maintenance method of fuel system
The top priority of this chapter, please take out your little book and remember the key points.
replace the fuel filter 1. Loosen the filter (1) and remove it; 2. Check whether the performance level of the new filter meets the requirements of the engine; 3. Fill the new filter with clean fuel; 4. Wet the new filter sealing ring with diesel oil; 5. Screw the new filter in place by hand until the sealing gasket contacts the support, and then continue to screw forward for 3 / 4 turn to lock it; 6. Ensure that all electrical components on the filter are installed in place; 7. Exhaust the air in the low-pressure system;
exhaust the air in the fuel system 1. Loosen the vent bolt of the fuel filter, as shown in the figure above; 2. Press the manual pump on the primary fuel filter until the fuel is discharged from the vent hole, and tighten the vent bolt; 3. If there is more air, start the engine to exhaust at idle speed.
drain water from the fuel system 1. Place a container under the primary fuel filter to collect liquid; 2. Unscrew the drain switch at the bottom of the primary fuel filter; 3. Drain the liquid until only fuel is visible, and tighten the drain switch.
precautions 1. Fuel is flammable. When working on the fuel system, be sure to keep cigarettes, open flames, beacon lights, arc equipment and switches away from the working area in a ventilated area to reduce the possibility of serious personal injury or even death. 2. Do not exhaust the fuel system on a hot engine; This may cause fuel to splash onto the hot exhaust manifold and cause a fire. 3. When testing the fuel injector, keep your hands and torso away from the fuel injector nozzle. The fuel pressure from the fuel injector is very high, which will penetrate the skin and cause serious personal injury. 4. The fuel pressure in the high-pressure fuel pipe is enough to penetrate the skin and may cause serious personal injury. Wear gloves and protective clothing when operating. 5. Try to avoid running the engine when the fuel is low, which will cause air or dust to enter the engine and cause damage.
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