Automotive carburetor working system and maintenance and breakdown.

Work System

Review

Such a simple carburetor can not meet the requirements of the mixture composition of internal combustion engines in various working conditions. Therefore, the carburetor used in general internal combustion engine, especially automobile internal combustion engine, also needs other systems, including main oil system, idle system, thickening system, acceleration system and starting system.

The Main Oil System

The main oil system is the main oil supply system of the carburetor. There are three commonly used main oil system correction (compensation) methods:
1. with infiltration air compensation;
2. oil needle to change the main hole area;
3. Change the area of the throat and the main measuring hole at the same time.

Among them, the first method is widely used. The air compensation method is to add the main air volume hole and foam pipe between the main volume hole and the nozzle, thus infiltrating the air, in order to reduce the vacuum of the main volume hole, so as to control the fuel flow, can get the required mixture composition. In order to make the mixture composition stable, the float chamber has a through hole communicated with the atmosphere, and the float controls the oil inlet needle valve to keep the liquid level of the fuel in the float chamber stable. The liquid level is usually 5 to 6 mm lower than the nozzle to prevent fuel spillover when the internal combustion engine tilts. The shape and size of the nozzle determine the air velocity and vacuum degree, thus affecting the internal combustion engine's charging capacity, main oil supply and fuel atomization. In order to get high speed airflow to make atomization good, and at the same time to increase the volume of air, can use double or triple throat. The main oil system can only meet the requirements of the mixture in most operating conditions. In special working conditions, the auxiliary system is also needed.

The Idle Speed System

When the internal combustion engine itself runs but does not work externally, it is called idle running. At this time, the throttle is nearly closed and the vacuum at the throat cannot suck out and atomize the fuel. Therefore, there is an idle nozzle behind the throttle, using the vacuum here to suck out the fuel. Idle oil gauge hole and idle air gauge hole are arranged in idle oil circuit to control oil gauge and make fuel foam. Idle speed can be adjusted by idle screw. In order to ensure the smooth transition from idle system to main oil system, there is a transition nozzle on the idle oil road between idle nozzle and throat pipe.

Economizer Concentration System

To meet economic requirements, the main oil system supplies a thinner mixture under most operating conditions. However, when the throttle is close to full open, maximum power is required, which requires the supply of a thick mixture. An economizer is usually used for this purpose. There are mechanical and vacuum economizers, the former using a lever associated with the throttle, and the latter using the vacuum behind the throttle to open and close the economizer valve. When the valve is opened, a portion of the fuel is added through the power oil volume hole to enrich the mixture, thus obtaining the maximum power.

To Accelerate The System

When the internal combustion engine accelerates, the throttle suddenly opens wide. The fuel mass is larger than the air, so the inertia is also large, it is difficult to increase the oil supply in time, and the mixture becomes instantaneous dilute, which makes the engine speed increase slowly, and even the intake pipe temper or stop. Therefore, there is a permanent accelerator pump, which is driven by the throttle through a pull rod and a spring. When accelerating, the accelerating pump will inject fuel into the throat; When the throttle is gently opened, the fuel returns to the float chamber through the intake valve of the accelerator pump and stops the injection.

Starting System

When the engine starts, the speed is very low, the temperature is also low, the atomization and gasification of fuel are very poor, so it requires the supply of a thicker mixture to ensure the starting combustion of the internal combustion engine, so it needs a separate starting system. Starting systems take many forms, the most common is to install a choke in front of the throat and close it when starting, so that a very high vacuum is formed at the throat, forcing the fuel to spew out a lot, forming a thicker mixture.

Normal Maintenance

The normal maintenance of carburetor is actually to keep the cleanliness of carburetor when it comes out of the factory, which is controlled as a key index of carburetor quality assessment in carburetor professional manufacturers, and strict control is carried out in each link of production by using various advanced equipment and technology. Therefore, in order to ensure the normal use of the carburetor, it is necessary to pay attention to the normal maintenance of the carburetor: regular cleaning of the carburetor, keep the carburetor oil passage, air passage clean, small aperture unobstructed. It is also very important to prolong the service life of carburetor. Many carburetor performance failures can be solved by regularly cleaning the carburetor.

1. carburetor is a key part of the engine, small changes may affect the vehicle performance. Therefore, in the process of carburetor disassembly, it is necessary to use appropriate tools and moderate strength to prevent parts from deformation. Disassembled parts should be placed orderly in order to prevent missing or wrong assembly in assembly.

2. Carburetor cleaning should be carried out in a clean place. First wipe the carburetor outside the surface, the internal parts of the cleaning can use carburetor special cleaning agent or industrial gasoline. In addition to impurities, pay attention to cleaning the surface of the parts of the gasoline gum. The cleaned parts should be blown clean with compressed air, and can not be wiped with cloth or paper that will produce burrs to prevent re-pollution. The blocked holes are forbidden to be opened by hard objects such as steel wire, to prevent changes in the performance of the carburetor caused by changes in the aperture, and should be cleaned out with gasoline or compressed air.

3. in the carburetor assembly process, the float chamber coupling screw, carburetor and engine coupling screw, do not tighten, must be tightened several times, the general tightening torque between 12N.m ~ 15N.m. Otherwise, the joint surface will be deformed, and there will be air leakage or oil leakage. Generally, the tightening torque of measuring hole parts is between 1.5n.m and 3.0n.m. If the tightening torque is too high, the thread will be damaged, the parts will be deformed, and even metal chips will be produced, which will cause secondary pollution and affect the carburetor performance.

4. In the process of cleaning the carburetor, if more sediment is found in the carburetor float chamber, it is often caused by the failure of the gasoline filter. At this time to check the gasoline filter, such as confirm its failure to clean or replace the new gasoline filter.

5. if the motorcycle is not used for a long time, it is necessary to exhaust the fuel in the carburetor float chamber to prevent the condensation of gasoline glue deposition, resulting in carburetor failure. In addition, it should be emphasized that: because the position of idle adjusting screw has an important impact on motorcycle emissions, idle speed, transition, fuel consumption and other performance, carburetor cleaning is generally prohibited to turn idle air adjusting screw. If it is necessary to remove idle air conditioning screw, the adjusting screw should be screwed to the end first, remember the number of twists (accurate to 1/8 turns), and return according to the original number of turns during assembly.

Fault Diagnosis And Elimination Of Carburetor Blockage

Carburetor vulnerable parts, its common fault diagnosis and elimination methods are as follows:

(1) Choke can not be fully open: this is the choke cable due to improper installation, too long or blocked, thus hindering the full opening and closing of the choke. The carburetor throat tube vacuum degree increase, the main nozzle oil supply is too much, increase the intake resistance, so that the amount of air into the reduction, resulting in too thick mixture, gasoline can not be completely burned, discharged to the exhaust pipe in fresh air combustion again; The mixture is too thick, the operation is unstable, the exhaust pipe gives out black smoke and is accompanied by a "sudden, sudden" sound; Sometimes shooting, power down, fuel consumption rose significantly.

In case of this fault, it is necessary to check the drag wire, remove oil rust, dry after dropping a little oil, until the assembly adjustment is appropriate, push and pull flexible so far.

(2) Rapid oil volume hole or rapid oil blockage: the intersection in the oil channel has sharp corner burr is not clean, resulting in oil or other fiber accumulation; The middle and lower body joint gasket installed, not installed or damaged, will affect the ability of fuel through the oil passage, or even blocked. At this time the engine can work normally, but in the rapid operation is unstable, easy to flameout or rapid too high, exhaust pipe issued "park, park" sound. The carburetor can be removed to repair the above parts, cleaning and dredge with compressed air if necessary.

(3) Idle air volume hole blockage: can not enter the appropriate idle air volume, resulting in thickening of the mixture, affecting the normal operation of idle, and can not play a role in inhibition, resulting in unstable ignition of the engine at the speed of rest, exhaust pipe discharge a large amount of black smoke and accompanied by "sudden, sudden" sound. It is normal when the car runs at medium and high speed, but once the engine is stopped and flameout for a moment, it is difficult to start, which is due to idle air volume hole blockage. When the idle operation is over after flameout, the engine inertia rotation from slowing down to stop there is a process. At this time, there is a certain suction in the intake pipe, and the fuel is constantly sucked out from the idle oil channel, and enters the intake pipe wall. At this time the gasoline pump has stopped working, so the float chamber fuel flow. In order to prevent siphoning, there are two air holes in the middle of the oil passage.

In idle working condition, the fuel sucked from the main oil passage is measured through the rapid metering hole and mixed with the air from the first idle air volume hole, and the air entered through the idle fuel saving hole and the second idle air volume hole are mixed twice to form a foam shape, and finally spewed out from the idle nozzle. At idle speed, the engine only keeps running and consumes little fuel. However, the idle nozzle under the throttle has a large suction force, and a small amount of air is introduced to reduce the vacuum degree of idle oil passage and reduce the fuel flow. When the engine flameout, the vacuum degree under the valve is very small. Although the oil level of the float chamber is higher than the rapid nozzle, the idle air volume hole is higher than the oil level. As long as the air volume hole is kept unblocked, the gasoline will not flow out from the float chamber through the idle oil passage after the engine flameout. Idle, when it is found that the exhaust pipe is emitting black smoke, and a "sudden, sudden" sound, or there is no oil in the float chamber, fuel oil overflow at the throttle shaft hole, should check whether idle air volume hole is blocked and dredged.

(4) Transition nozzle clogging: as the growth of the car mileage, the dust in the air and oil adsorption around the hole, hole make the air volume of the narrow cross-sectional area, the volume decreased, moreover, get rich mixture, improper assembly adjustment, or because of too much carbon deposit dirt, will cause the transition out of the oil hole blockage, affect the transition out of the oil in the morning and evening time when and how much.

The transition nozzle is blocked, affecting the smooth transition from low speed to medium speed or medium speed to low speed; At the same time, when idle, the air can not enter the oil passage by the transition nozzle, causing the effect of the second idle air volume hole, so that the gasoline bubbles again, can not get the appropriate amount of emulsion oil. When the throttle opens quickly, the idle nozzle releases less fuel rapidly, while the transition nozzle provides more fuel for a short period of time to help the engine rev up. If the transition nozzle is blocked, it can not play the role of supplementing fuel, resulting in poor acceleration. When the engine suddenly opened in the throttle moment, carburetor backfiring, it may be the transition nozzle blockage or carburetor rapid acceleration device fuel shortage.

During maintenance, the throttle will be opened and closed rapidly in a continuous period from almost closed to small load. At this time, if there is still a backfiring phenomenon, the transition nozzle will be blocked, and the fault can be eliminated after dredging.

(5) Main oil volume hole, foam pipe and main nozzle blockage: the main nozzle around the seepage hole (foam hole) is blocked by dirt (or partially blocked), through the air volume hole oil well (the following part of the air volume hole) into the air, can not penetrate into the main nozzle to form foam mixture, resulting in poor fuel atomization. When the engine is not loaded, step on the throttle, the speed is not easy to improve, carburetor backfire; When driving, it feels insufficient power, easy to flameout quickly and difficult to start.

During maintenance, step on the accelerator pedal continuously and fill oil in the throat tube with the rapid acceleration device. If the operation is normal and the flameout phenomenon disappears, the main oil supply device is blocked, which can be decomposed and cleaned to dredge and replaced with new parts if necessary.

6) The main oil supply unit quantity of air hole jam: carburetor main orifice (and primary nozzle) is to determine the key part of mixing ratio, it through the air quantity of hole to penetrate into the air, and to reduce the pressure difference between before and after the orifice, controlling the fuel flow, in order to adapt to the request of the engine to the mixture under various working conditions, to make the fuel consumption of the most reasonable and economic. Air through the main air volume hole, on the one hand with the increase of the throttle opening, the vacuum at the throat increases accordingly; On the other hand, gasoline bubbles.

Air volume hole blockage will reduce the amount of air entering, will lead to the increase of the flow and flow rate of gasoline, resulting in a thickened mixture, affecting the atomization and combustion of gasoline, while significantly increasing fuel consumption. When maintenance, decomposition cleaning and dredge the main air volume hole, the fault can be completely eliminated.

(7) The oil channel or quantity hole of the mechanical thickening device is blocked: the function of the mechanical thickening device is to provide extra oil when the engine is under large and full load, to ensure the requirements of the mixture concentration under the working condition, and to compensate the thickening effect. If the oil channel or volume hole of the device is blocked, the mixture is too thin at large load (throttle opening 80%-85%), and the power is insufficient at this time (commonly known as boring), and the exhaust pipe emits the sound of "park, park". Repair, with rapid acceleration to the carburetor oil, such as "park, park" sound disappeared, it can be judged as the thickening device (oil channel or volume hole) blocked.

(8) Oil channel or airway blockage of the vacuum thickening device: the vacuum thickening device relies on the pressure difference between the upper and lower throttle at the throat pipe to make the extra fuel flow into the main nozzle through the thickening hole to compensate for the lack of oil out of the main hole, so that the mixture is thickened and the engine can obtain the required concentration of mixture at large load and full load.
If the oil passage and quantity hole of the vacuum thickening device are blocked, or the gasket is improperly installed, the ventilation passage of the vacuum thickening device is blocked, so that the vacuum effect will be lost, resulting in the frequent oil supply or oil flow is not smooth, and the thickening effect will be lost. When the engine due to load increase, speed significantly decreased, the exhaust pipe issued "park, park" sound, encountered the above phenomenon to dismantle the vacuum thickening device, with compressed air dredge air passage, oil passage and volume hole.

(9) Acceleration of oil and gas channel blockage: when the acceleration device suddenly opens the throttle, a certain amount of extra fuel will be sprayed into the throat pipe in time, so that the mixture can be temporarily concentrated to meet the needs of engine acceleration. When the oil and gas channel is blocked, unstable oil or no oil will occur, leading to poor engine speed transition, thus increasing fuel consumption. The reasons are as follows: the speedier pump oil cabinet is stuck by dirt; Acceleration nozzle or oil passage blocked and failure; The gas hole above the acceleration pump is blocked, etc. When the engine is stepping on the accelerator pedal rapidly, if the engine speed is not easy to improve, sometimes there is serious backfiring phenomenon, even engine flameout, that is, rapid acceleration fault.

During maintenance, open and close the throttle continuously suddenly, and check whether there is fuel ejection from the accelerator pump nozzle from the carburetor mouth. If there is no fuel ejecting, the fault in the accelerator pump or the acceleration orifice is blocked. First remove the carburetor cover, the float chamber is filled with gasoline, quickly open and close the throttle, so that the rapid acceleration pump piston reciprocating movement. If the piston downward movement resistance is very large, it is the rapid acceleration nozzle or oil blockage. At this time must decompose, clean the oil lot, the lot and its air vent, and blow clean and dredge with compressed air.

(10) The balance vent of the float chamber is blocked: the balance vent of the float chamber is a connecting pipe vent between the upper part of the closed float chamber and the carburetor air inlet. When the air cleaner is gradually blocked in the process of use, the intake resistance increases correspondingly, and the pressure on the float chamber also changes, so that the mixture concentration is not affected by the change of air cleaner resistance.

If the balance vent is blocked, the carburetor oil supply will be insufficient or even stop. If the hole is blocked artificially, the vacuum in the float chamber will lead to no rapid or rapid instability, and the high speed shooting will be caused by the reduction of oil supply and dilution of the mixture. After the balance vent is blocked, the cold and hot car is good to start, and the medium speed is normal, but the speed is easy to flameout. In any case, the speed can not be adjusted. Therefore, it is necessary to keep unblocked and avoid artificial failure as far as possible.

Points Needing Attention In Maintenance Of Carburetor Blockage

The user should often carry on the correct maintenance to the carburetor, not only can prolong the service life of the carburetor itself, but also can make the carburetor in the excellent working state, reduce the engine failure and the wear of the cylinder block, improve the performance of the engine, prolong the service life of the whole machine. The air filter should be cleaned frequently to check that the connection to the carburetor is tight. If the air is not purified and enters the carburetor, it is easy to cause the airway blockage, the mixture is too thick, the rapid instability, the fuel consumption increases and so on, and the wear of the piston parts is aggravated when it is serious.