Fuel consumption directly depends on the condition of the fuel system, and if there are faults in it, the car's dynamics also deteriorate and the engine begins to operate unstably.
This article will discuss the K151 carburetor: design, repair, adjustment, configuration features, as well as the main problems and their symptoms.
K-151 carburetor design
In the fuel system, the carburetor of the K-151 model performs the function of preparing the air-fuel mixture in the composition necessary for the operation of a car engine under various loads - at idle, at medium or maximum speed. This unit is used on Volga and IZh passenger cars, Gazelle and Sobol commercial vehicles, and UAZ SUVs. There are various modifications of the “one hundred and fifty-first”, and depending on its model, a letter is added to the name at the end, for example, the GAZ-3102/31029, GAZ-3302 “Gazelle” cars are equipped with the K-151S carburetor. Also, depending on the K-151 model, jets can be installed with different sections - much depends on the characteristics and size of the engine.
The 151 series carburetor consists of the following systems and elements:
- main body (middle part) with a float chamber;
- throttle body – the valves rotate due to the drive connected to the accelerator (gas) pedal;
- the top cover of the float chamber - it contains a locking mechanism that prevents the chamber from overfilling with gasoline, as well as an air damper necessary for starting a cold engine and warming it up;
- main dosing system - is the main one in the preparation of the air-fuel mixture (FA), consists of channels of a certain cross-section, two fuel and two air jets;
- idle system, which is necessary for stable operation of the internal combustion engine at idle speed - it includes a bypass channel, adjusting screws (quality and quantity of fuel assemblies), jets (fuel and air), an economizer valve with a membrane mechanism;
- accelerator pump - it allows the car to drive without failures during sudden acceleration, consists of additional channels in the main body, a ball valve, a diaphragm mechanism and a fuel sprayer;
- econostat - the system is designed to enrich fuel assemblies at high engine speeds; it represents additional channels through which, under the influence of high vacuum when the throttle valves are open, an additional portion of fuel enters the intake manifold;
- transition system - it is needed for a smooth increase in speed at the moment the throttle valve begins to open in the secondary chamber; it consists of fuel and air jets.
The K-151 carburetor consists of two chambers, the throttle valves in it open sequentially, and a filter - a protective mesh - is installed at the inlet of the fitting. The unit is also equipped with a return fuel line, through which excess gasoline is discharged back into the gas tank; also, the “return” does not allow the creation of overpressure fuel. The design of the K-151 carburetor itself is quite complex, and in order to repair and adjust the unit, you need experience and strict adherence to the repair instructions.
Several hoses of two diameters are connected to the K-151 carburetor - if they are mixed up, the engine will not work properly. We connect the hoses in the following order:
Adjustment
If without experience it is quite difficult for car owners to repair the K-151 unit with their own hands, then it is easier to master the adjustment, the main thing is to understand the principle of operation of the device and act according to the instructions. There are several types of “one hundred and fifty-first” adjustments:
- idle move;
- air damper position;
- gasoline level in the float chamber;
- throttle position.
Changing the fuel level in the float chamber should be trusted to experienced carburetor specialists, but any driver can adjust the idle speed independently. We carry out the procedure as follows:
If the engine speed is high, you should reduce it using the screw that adjusts the position of the throttle valves. This screw often boils tightly, and it is impossible to turn it in any direction (in the picture below, under the number 4, under the white paint). 
There is one “tricky” way to force the adjusting element to turn - you need to install a flat-head screwdriver in its slot and carefully hit it several times with a hammer (you need to feel the force, otherwise you can break parts of the carburetor). The screw will “come away” and begin to rotate on the thread. If the “trick” does not work the first time, it should be repeated. It is important to take your time and be patient, then everything will work out.
Repair
During the operation of the car, various malfunctions may occur in the carburetor; the main signs of malfunctions in this device are:
- increased fuel consumption;
- black smoke from the muffler pipe, it is especially noticeable if you press the gas pedal sharply;
- unstable operation at idle, the engine may also stall when the speed is reduced;
- poor car dynamics;
- failures when accelerating.
If the carburetor is faulty, the engine may not develop speed, and popping noises and shots from the muffler are often heard in the intake manifold. K-151 is a rather complex unit, and almost any of its elements can fail.
There are reasons why a carburetor most often fails:
- jets, fuel and air channels become clogged;
- heating causes deformation of the body;
- the float chamber shut-off valve stops working;
- Over time, the jets wear out.
Many repairmen, when restoring the functionality of the carburetor, first of all try to replace the jets, believing that because of them, fuel consumption increases and the engine runs unstable. One rather important note - the jets wear out very rarely, and most often wear occurs when the carburetor is often operated in dusty conditions. The most common reason for poor carburetor performance is its clogging, but in order to thoroughly clean the unit, it is necessary to completely disassemble it. Repair of the K-151 carburetor is carried out with the removal of the device, complete washing and purging of all its parts.
Often, car owners switch cars with carburetor engines to gas; for example, it is profitable to install LPG on a working Gazelle. But with the constant use of gas in the carburetor, various types of problems appear, and one of them is a malfunction of the cold start system on the carburetor.
On many cars, the gas system uses a gas spacer for the K-151 carburetor; it is placed between the main body and the throttle body. Due to the additional insert, the distance between the lower and upper parts of the carburetor increases, so the cold engine starting system begins to work irregularly - you have to constantly keep your foot on the gas pedal, while holding the choke. On gas, a choke that is not fully working does not affect the operation of the engine, but the whole point is that cold starts of the engine, and especially in winter, are carried out on gasoline. Therefore, it is quite problematic to start the internal combustion engine with the air damper not completely closing; even due to the resulting vibrations, the fastening of the damper axis is often unscrewed. How to get rid of such an unpleasant problem?
One of the options for solving the problem is to weld an additional strip onto the air damper rod, which allows you to compensate for the difference in the thickness of the standard gasket between the housings and the gas spacer. 
The bar can be made from an electrode with a diameter of 2 mm.
If the parts are severely worn, the carburetor needs to be replaced; most often it is changed if the housing wears out:
- the lower surface of the middle part is severely deformed;
- the cover (upper part of the body) is warped;
- The seat for the throttle valves in the lower part wears out.
The price of a new K-151 carburetor is quite high (on average 5.5-6.5 thousand rubles), but it is impossible to drive with a faulty device, especially since with high fuel consumption even more money is lost. Changing the K-151 is quite simple; let’s look at the process of replacing it on a Gazelle car:
If malfunctions occur in the carburetor accelerator pump, the engine begins to “choke” and failure occurs when the engine speed increases sharply. Quite often, the reason for such operation of the internal combustion engine is a clogged “nose” of the fuel nozzle; the accelerator pump diaphragm can also fail.
Diaphragm defects are determined by its external inspection; it can be easily reached without removing the carburetor from the engine. To do this, you need to unscrew the four screws of the cover (number 11 in the picture below), but you need to remove it carefully - it is important not to lose the spring, which is located inside the unit. 
To determine the serviceability of the accelerator pump atomizer, you need to remove the air filter housing, turn the throttle valve by hand and see if fuel flows through the “spout” of the accelerator. If the nozzle is clogged, you can try to blow it out, but this will require removing the carburetor cover. If the spout does not blow through, it should be replaced; the work of replacing it is also carried out without removing the entire assembly. We replace the accelerator pump nozzle as follows:
If the engine consumes a lot of fuel, one of the reasons for this phenomenon may be a faulty needle valve in the float chamber - it is not sealed, and too much gasoline enters the chamber. In some cases, the valve completely stops holding fuel, then the carburetor is completely filled with gasoline, and the car does not start. Changing the needle valve is very simple:
K-151 carburetors, like any other carburetors, are devices for precise dosing of fuel in the air flow, formation of a combustible mixture from fuel and air and regulation of its supply to the engine cylinders.
Carburetors have two side-by-side vertical channels for air passage, at the bottom of each of which a rotary throttle valve is installed.
Each of the channels is called a carburetor chamber.
Since there are two such channel-chambers, and the throttle valve drive is designed so that as you press the accelerator pedal, first one and then the other valve opens, carburetors of this type are called two-chamber with sequential opening of the chambers.
The chamber in which the throttle valve opens earlier is called primary, the other is called secondary.
In the middle part of each of the main air channels there are cone-shaped constrictions-diffusers, through which a vacuum is created in the air flow, necessary for sucking fuel from a special container located in the carburetor body - the float chamber.
The fuel level in the float chamber required for normal operation of the carburetor is maintained constant (more precisely, almost constant) using a mechanism with a float and a shut-off needle.
It should be noted that the float mechanism of the K-151 carburetor is fundamentally different from the similar device of all other domestic carburetors: it is completely, together with the needle and float, housed in the carburetor body and is accessible for visual inspection after removing the cover, without disturbing the natural interaction of the float with the fuel level.
The carburetor consists of three main parts:
The top one is the housing cover, with a flange and studs for fastening the air filter, with a ventilation device for the float chamber and parts of the starting device, with seven screws for fastening to the carburetor body through a cardboard gasket;
Middle - carburetor body, with a float chamber and a float mechanism, a fuel supply fitting and fuel metering systems;
The lower one is the throttle body, with the throttle valves and their drive mechanism, as well as with the idle device attached to the carburetor body from below with two screws through a composite gasket consisting of two thin ones - cardboard and one thick one - plastic.
The carburetor contains the following systems, devices and mechanisms:
Float mechanism;
Fuel and water metering systems;
Main dosing systems of the primary and secondary chambers;
Idle system;
Secondary chamber transition system;
Econostat;
Acceleration pump;
Starting device;
Economizer valve for shutting off fuel supply in forced idling mode (EFI);
Forced crankcase ventilation system;
Float chamber ventilation system;
Throttle valve control mechanism.
The K-151, K-151D carburetor is installed on engines of models 402 and 4021.
Rice. 1. Diagram of carburetors K-151, K-151D
The K-151 carburetor (Fig. 1) consists of three main detachable parts, connected through sealing gaskets with screws.
The upper part - the carburetor cover includes an air pipe, divided into two channels, with an air damper in the channel of the first chamber.
The middle part consists of a float and two mixing chambers and is the carburetor body.
The lower part - the throttle body includes mixing pipes with the throttle valves of the first and second carburetor chambers.
The gasket between the middle and lower parts of the carburetor is sealing and heat-insulating.
Structurally, the carburetor consists of two mixing chambers - the first and second.
Each of the carburetor chambers has its own main metering system.
Idle system- with quantitative regulation of constant mixture composition (autonomous idle system).
In the second chamber of the carburetor there is a transition system with fuel supplied directly from the float chamber, which comes into operation when the throttle valve of the second chamber opens.
The accelerator pump is diaphragm type. To enrich the combustible mixture at full load, an econostat is provided in the second chamber.
Rice. 2. Scheme of a semi-automatic starting and warming up device
Cold starting system (Fig. 2) - semi-automatic type, consists of a pneumatic corrector, a system of levers and an air damper, which is closed by the driver using a manual drive before starting a cold engine.
When the engine starts, the pneumatic corrector, using the vacuum that occurs under the carburetor, automatically opens the air damper to the required angle, ensuring stable operation of the engine when warming up.
When pulling out the choke lever, you must press the accelerator pedal.
Fuel cut-off system (forced idle economizer) comes into operation in forced idle mode when the vehicle is braking by the engine, when there is no need to supply fuel to the engine.
This ensures fuel savings and reduces the emission of toxic substances into the atmosphere.
The K-151 carburetor fuel shut-off system consists of a control unit 33 (see Fig. 1), a microswitch 35 of the solenoid valve 32 and a forced idle economizer.
The microswitch and forced idle economizer are located on the carburetor, the solenoid valve - the control unit - on the front panel of the cab.
Control block 33 is a device that, depending on the frequency of electrical pulses coming from the ignition coil, controls the solenoid valve 32.
When the accelerator pedal is released, the contacts of microswitch 35 should be open.
The fuel shut-off system works as follows.
When the accelerator pedal is released and the engine speed is more than 1400 rpm -1, the control unit does not supply voltage to the solenoid valve, as a result of which atmospheric air enters the forced idle economizer through the channels of the solenoid valve, the valve of which closes the idle channel.
If the normal operation of the fuel supply shut-off system is disrupted (the engine does not start or “stalls” when the throttle pedal is released), you must first make sure that the electrical contacts of the system elements are reliable, after which you should sequentially check the functionality of the solenoid valve, microswitch and control unit.
For checking the solenoid valve and microswitch It is necessary to disconnect the electrical connector of the control unit, turn on the ignition (do not start the engine!) and from the engine compartment with one hand smoothly open and close the carburetor throttle valves several times, and with the other hold the solenoid valve.
If the solenoid valve and fuse are working properly and if the microswitch is working properly and correctly adjusted, you should feel the activation of the solenoid valve (vibration, clicks).
To check the control unit you need to insert the connector into the block, turn on the ignition, start the engine and warm it up.
Then, from the engine compartment side, open the throttle valves approximately ⅓ of the stroke with one hand, and hold the solenoid valve with the other.
Release the throttle valves sharply.
In this case, if the control unit is corrected, the solenoid valve should turn off, and when the crankshaft speed decreases to approximately 1050 min -1, the solenoid valve should turn on.
All carburetor systems are connected to a float chamber, the fuel level in which is maintained by float 2 and fuel valve 1 (see Fig. 1).
The main metering elements of carburetors are given in table. 1.
Table 1. Main metering elements of carburetors K-151 (ZMZ-402), K-151D (ZMZ-406)
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Options |
First camera |
Second camera |
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Main fuel jet, cm 3 /min |
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Main air jet, cm 3 /min |
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Idle jet block, cm 3 /min: |
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idle tube |
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emulsion tube |
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Idle air jet |
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Idling emulsion jet |
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Transition system fuel jet, cm 3 /min |
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Air jet of transition system, cm 3 /min |
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Diameter of the accelerator pump nozzle hole, mm |
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Diameter of the hole in the econostat screw, mm |
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Diameter of the fuel bypass hole into the tank, mm |
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Fuel valve seat diameter, mm |
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Diffuser diameters, mm: |
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The mass of the float assembly is no more than 12.5 g. |
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For most owners of Volgas, Gazelles and UAZs, the domestic industry has not left much space for choosing a more or less successful carburetor model. The manufacturer simply equips a modern gasoline engine up to 3000 cc with K-151 series carburetors. The position is simple; whoever doesn’t like it can use the outdated K-126. With proper adjustment, the K-126G carburetor can successfully replace the more sophisticated 151 series on the Volga.
Guarantees for normal carburetor operation
Before deciding to replace the K-151 carburetor with a K-126G or K126GU, take a closer look at the K-151S. In many cases, the reputation of the K-151C carburetor, its repair and adjustment, is practically no different from other models in this series, and the quality of work is ensured by a number of improvements:
- diffusers have an improved chamber channel profile;
- the optimized profile of the accelerator pump cam drive allows full supply of fuel to the two chambers in the required volume;
- the damper drive rotates steplessly, providing precise positioning, which facilitates cold starting of the engine;
- The adjustment ranges for the metering screws have been changed, which significantly increases the dynamics of the engine while maintaining gas toxicity standards.
The manufacturer claims a theoretical improvement in dynamics by at least 5-7% when installing the K-151S.
Important! One of the reasons for the abnormal operation of the K-151d carburetor, requiring adjustment and repair, is a large number of outright defects in new carburetors sold in retail chains.
For normal operation, the K-151 carburetor requires repair and adjustment, otherwise the carburetor exhibits instability of characteristics and increased fuel consumption. To achieve more or less stable operation, you need to check the adjustment of the main adjustment points:
- Check the proper operation of the EPHH K-151 and all system components. Often, the main reason for poor performance of the positive stroke system may be incorrect factory assembly of the relative position of the valve spring and diaphragm.
- Adjust idle speed with diagnostics or repair of individual components.
- Check and adjust the action of the accelerator pump.
- Poor quality gasoline leads to the accumulation of dirt in the float chamber. For repairs and adjustments, it is necessary to first purge the main air and fuel channels, and sometimes check the condition of the jets.
Differences in approach to K-126 and K-151
The basic principles of repair and adjustment are practically the same for both lines of K-151 and K-126 carburetors, with the exception of the specific operation of the pneumatic valve and the K-151 electronic unit. More problems arise when some carb components are incorrectly replaced with spare parts of a different model.
Often, after replacing the K-151 carburetor with the simpler K-126 model, a number of problems arise. First of all, the poor quality of the lower carburetor block leads to the formation of cracks, air leaks and a sharp leaning of the mixture. To prevent breakage, it is necessary to carefully align the mating plane on sandpaper glued to the glass.
In some cases, adjusting and repairing the K-126 carburetor does not make sense at all due to significant wear at the interfaces of mechanical parts, for example, in the support holes of the damper axis or rods, and the threads of the adjusting screws. In such places, leakage and evaporation of gasoline may occur with simultaneous air leakage. They are easily recognized by the icing that has formed on the body of the K-126 carburetor.
Adjusting the K-151 carburetor
The adjustment procedure is not particularly difficult, but if you have no experience, it is better to study the adjustment of the K-151 carburetor in the video:
The old Soviet school of carburetor construction ensures that the K-151 or K-151E can be repaired and adjusted using a simple or Phillips screwdriver.
Monitoring the level of imbalance of the float chamber K-151
For normal operation, a properly functioning valve is required to compensate for the air pressure in the float chamber. If problems arise with the operation of the balancing valve, fuel consumption jumps sharply, and it is useless to adjust it. At the same time, the click of the drive does not at all indicate pressure balancing; before repair, it is better to check by replacing it with a known-good version. For further adjustments of the K-151, you should first clarify and adjust the fuel level in the float chamber.
Setting idle speed K-151
We carry out a simple procedure for setting idle speed in the following order:
- warm up the engine to operating temperature;
- Using a screwdriver, we display on the tachometer the position of idle speed 550-650 (for a three-liter 700-750). the large screw is easy to see on the rear wall of the carburetor;
- Using the screw for setting the air-fuel mixture, we turn out the maximum engine speed;
- use the idle speed adjustment screw to raise the idle speed by a hundred more than necessary;
- Use the mixture quality screw to set the required idle speed K-151.
Let's check the result. At a speed of 1400-1500 rpm, sharply press and close the throttle. It is normal if the speed does not drop below the set idle speed. In this case, there should be no twitching in the engine operation. While on the move, when accelerating and accelerating, there should be no dips in engine thrust.
Important! The procedures carried out make sense only in the case of a fully functional and adjusted motor.
Let's work with the throttle position screw
The carburetor design uses a thrust screw for adjustment and repair, which limits the extreme position of the damper. The thing is very useful, but there is a nuance. The screw tends to self-tighten, thereby leaving the damper suspended. The damper begins to rub against the walls of the chamber and after a certain period of time wedges in the extreme position.
To prevent this situation, after adjustment, the screw should be secured with a drop of paint.
If you have good mechanic repair skills and a desire to “sharpen” and adjust the K-151 carburetor to suit your car, choose K-151S. Otherwise, the old, reliable K-126G, or for vehicles with off-road properties with the GU index, will do.
The K-151 carburetor is designed to equip ZMZ four-cylinder power units with a volume of 2.45 liters, which were once equipped with cars of the GAZ and UAZ families. The production of three modifications of the engine power supply device has been launched: K-151, K-151V and K-151N. The K-151N modification is more focused on UAZM engines.
Like all components and assemblies in the car system, the carburetor must be regularly maintained and repaired at the first symptoms of a malfunction. In this article we will look at the features of the design, adjustment, repair and connection of the K-151 carburetor.
Device design
To ensure that the engine can operate at any speed, the carburetor prepares the fuel-air mixture. Despite the fact that the individual systems of the K-151 carburetor are made according to standard designs, all three modifications differ from other devices in their layout. The advantage of the K-151 is the shut-off needle located in the body, which greatly simplifies the adjustment of the gasoline level. In general, the entire assembly can be divided into three parts with a base in the form of a float chamber.
Other important design elements are:
- Locking mechanism located in the top cover of the float chamber;
- Dosing system consisting of air and fuel jets;
- Adjusting screws and economizer valve of the XX system;
- Eliminates dips during vehicle acceleration using a special accelerator pump with a fuel sprayer;
- At high speeds, the fuel assembly enriches the econostat;
- A transition system is necessary to gradually increase the number of revolutions at the moment the secondary chamber opens.
The K-151 received two chambers, which guarantees continuous movement of fuel in the event of any breakdown. The fuel level is adjusted automatically due to the ability to close the valve opening with a shut-off needle. The operating principle is as follows: if there is not enough gasoline in the chamber, the float lowers and releases the needle. As the chamber fills, the float rises, followed by the needle closing the valve cross-section. The lower compartment houses the primary and secondary throttle valves with control actuators. During operation, they open alternately, fuel passes through a mesh filter mounted in the fitting, due to which gasoline enters the system without impurities and inclusions.
Service
Carburetors are reliable and unpretentious devices. K-151, like other components in the automotive system, requires periodic maintenance. Basically, problems arise in the event of unqualified intervention in its design or due to inappropriate maintenance. Neglecting the simplest maintenance procedures for the K-151, it may happen that the carburetor ceases to function fully due to the clogging of the calibrated holes with hard tarry deposits. For its correct operation, it is necessary to timely adjust the main systems.
Idle speed adjustment
The design of the K-151 does not allow dirt and dust to penetrate directly into the unit; in addition, during its operation, due to the movable joints, self-cleaning of the most important functional elements occurs. A simple but extremely effective layout allows even a dirty K-151 carburetor to work no worse than an absolutely clean copy. But at least 1-2 times a year you should clean it from the outside using compressed air. This is the minimum required maintenance for the device. Don't forget about adjusting the most important systems.
Adjusting the XX on the K-151 carburetor is necessary for normal engine operation. A properly operating engine contributes to the formation of a minimum amount of carbon monoxide in the exhaust gases. Since most car enthusiasts do not have even the most ordinary gas analyzer at their disposal, monitoring the operation of the system is not so easy. But there is a way out of this situation - it’s enough to arm yourself with one.
The procedure is as follows:
- Initially, the engine warms up, then the quality screw rotates until the maximum idle speed is established. In this case, the quantity screw remains in the same position.
- Afterwards, the speed is set to exceed the initial value by 100-120 rpm.
- It is recommended to do the above steps twice to be on the safe side.
- Then the quality screw is tightened until the speed reaches a normal value.
It is especially effective to adjust the idle speed if you have a high-precision tachometer. Such work can be carried out at any time, but it is most advisable to do it two or three times within one year.
Adjusting the float mechanism
Any carburetor adjustment must include adjusting the float mechanism - a responsible and extremely important task. But no difficulties in carrying out such work should arise even for those who have only recently become owners of a car with a carburetor power system. However, it is worth understanding that any inaccuracies in the adjustments can lead to further interruptions in the operation of the power system. This is why it is important to prepare thoroughly before you begin manipulating this mechanism.
Procedure:
- The upper part of the housing is removed.
- About a quarter of the fuel is pumped out.
- The crankshaft is installed in such a position that nothing interferes with the movement of the fuel pump diaphragm.
- Gasoline is pumped in manually.
- Once the required fuel level is set, the shank of the caliper with the height set at 21.5 mm is lowered between the wall and the shut-off needle.
When adjusted, the shoulders of the caliper will rest against the top of the body, and the shank will come into contact with the fuel. At a low level, the tongue must be bent upward, and at a high level, accordingly, downward. It is important to drain the fuel from the chamber each time after changing the position of the tongue.
Over time, various breakdowns can occur with the carburetor, because all its elements have their own resource. Most often, a faulty K-151 unit provokes increased fuel consumption and reduces the dynamic performance of the vehicle. There are often cases when black smoke pours out of the exhaust pipe, and the car refuses to pick up speed at all. All these problems with the car in most cases are caused by a malfunction of the fuel system. The operation of the K-151 is greatly affected by various deposits that interfere with the normal operation of the jets. You can check their condition and clean the jets quite simply, but to do this you need to disassemble the carburetor itself.
Let's disassemble the mechanism
It is advisable to completely disassemble the assembly in cases where there are no other possibilities to get to any structural element. To check the condition of the jets and clean them, simply remove the top cover of the housing. You can carry out all the work quickly and efficiently with the help of an arsenal of the necessary tools.
The procedure for completely disassembling the K-151 carburetor is as follows:
- Remove it from the cotter pins by unscrewing the four nuts.
- Clean the housing from dirt and dust.
- Loosen the seven cover screws.
- Remove the special cotter pin and rod.
- Loosen the two float chamber screws.
- Remove the econostat sprayer.
- Turn the seats of the needle valve with the horn to “12”, and unscrew the screw of the filter fittings to “22”.
- The fuel filter is removed along with the gaskets, after which the float chamber itself is dismantled.
Further disassembly of the K-151 involves dismantling the air and fuel jets, the idle speed unit, the accelerator pump and removing the quality screws. The carburetor must be completely disassembled at the time of its comprehensive flushing. Most auto mechanics prefer to completely replace the jets with new ones. For these purposes, you can use the jet table. But it is worth saying that they fail only in exceptional cases. Often, washing and blowing them is enough to restore their previous functional properties.
Assembling and connecting hoses
When assembling the unit, you must be extremely careful. It is important to remember the order in which the mechanism is disassembled and during assembly proceed in the reverse order. All elements should be installed in their places and securely fastened. Initially, quality screws and two screws are screwed into the empty housing to secure the throttle valves.
Old or new jets are screwed into the sockets, the fuel block and idle are connected. After which the float chamber is installed and secured. It is important not to forget to replace the float and needle itself. Many domestic drivers are also faced with the need to connect the K-151 carburetor hoses to the ZMZ-402.
The photo shows a diagram of the K-151 carburetor.
All hoses and tubes are connected in the following way:
- The largest fuel supply pipe is connected to the float chamber.
- A fuel return hose is connected to the lower outlet of the carburetor.
- Smaller diameter hoses are connected to the economizer and to the throttle valves.
- Then the vacuum hose is connected.
- The forced ventilation hose is connected to the top terminal of the carburetor.
Connecting the hoses is a fairly simple and easy job. But a beginner can easily get confused about their purpose, so at the first stage it is recommended to leave the corresponding markings on their surface with a marker while disassembling the carburetor. By taking simple steps to clean the carburetor parts, you can significantly extend not only the service life of the K-151, but also the main power unit of the car.
Conclusion
Adjusting, repairing and connecting the K-151 carburetor requires patience and perseverance from the car owner. The work is quite extensive, but the adjusted and cleaned mechanism works several times more efficiently. The K-151 is structurally complex; absolutely any part in it can break; in some cases, it will have to be completely disassembled. A beginner is unlikely to be able to handle such a task, but if you have some free time and patience, you will be able to solve any problem yourself in your own garage. Most often, problems arise due to various contaminants - especially jets. It is important to monitor the condition of the entire unit and regularly clean it of combustion products.
With the UMZ-4178 and UMZ-4179 engines, K151V carburetors are installed, with the UMZ-4218 engine - K151E carburetor, with the ZMZ-4021.10 engine - K151U, with the ZMZ-4104.10 engine - K151TS. The design of the carburetors is the same, with the exception of some metering elements.
Carburetors K151V, K151E, K151U, K151TS engines UMZ-4178, 4179, 4218 and ZMZ-4021, 4104, device.
Carburetors K151V, K151E, K151U, K151TS engines UMZ-4178, 4179, 4218 and ZMZ-4021, 4104 have a semi-automatic system for starting and warming up the engine and an autonomous idle system with a forced idle economizer (EFH).
The starting and warming up system is semi-automatic, correcting the mixture composition after starting the engine depending on the vacuum in the throttle space. An autonomous idle system reduces fuel consumption and exhaust emissions.
The operation of the EPHH is controlled by an electromagnetic valve installed on the vehicle, an EPHH control unit and a microswitch installed on the carburetor. The electronic unit ensures that the electrical circuit of the solenoid valve closes at a crankshaft speed of less than 1050 rpm and opens the circuit at a speed of more than 1400 rpm.
The microswitch closes the circuit when the throttle control pedal is pressed and opens when the pedal is fully released, the manual throttle control handle is recessed all the way in all cases.
When the circuit is closed, the solenoid valve communicates the throttle space with the diaphragm cavity of the EPHH valve. Under the influence of vacuum, the valve is in the open position, ensuring the flow of emulsion from the idle system. When the circuit is open, the solenoid valve closes the vacuum supply channel, the EPHH valve closes, stopping the flow of emulsion from the propulsion system.
Thus, the EPH valve is open:
— with the throttle valve open, the accelerator pedal is pressed;
— with the throttle valve closed, the pedal is completely released if the crankshaft speed does not exceed 1050 rpm.
The EPH valve closes (economy mode) when the engine brakes, the pedal is completely released if the rotation speed exceeds 1400 rpm, and remains in the closed position until the crankshaft speed drops to 1050 rpm, or until the throttle is reopened damper When the ignition is turned off, the EPH valve also shuts off the supply of emulsion from the idle system, which eliminates the possibility of spontaneous operation of a hot engine - glow ignition.
To achieve the greatest fuel economy, you must ensure that in the forced idling mode the throttle control pedal is completely released, since at the slightest opening the microswitch is triggered and the forced idling economizer is turned off.
It is carried out using a pedal connected by a system of rods and levers to the throttle valve, and control handles for the throttle and air dampers of the carburetor. The handles are connected to the dampers using flexible rods.
The position of the rods is fixed by rotating them around their axis 90 degrees in any direction. When the car is moving, the carburetor manual control handles must be pushed in all the way.
Maintenance of carburetors K151V, K151E, K151U, K151TS.
It consists of periodically checking and adjusting the fuel level in the float chamber, adjusting the low speed of the engine crankshaft, checking the operation of the accelerator pump and economizer, cleaning, purging and flushing carburetor parts from tar deposits, checking the throughput of the jets.
Checking the fuel level must be done with the car engine not running and installed on a horizontal platform. The fuel level in the carburetor float chamber should be within 20-23 mm from the plane of the float chamber connector. Adjustment is made by bending the float tongue, while the float should be in a horizontal position. The valve stroke is adjusted by a tongue and should be: on UMZ-4178, 4179, 4218 engines -1.5-2.0 mm, on ZMZ-4021, 4104 engines - 2.0-2.3 mm.
Adjusting the minimum crankshaft speed in idle mode.
This is done on a warm engine using the idle speed adjustment screw, and the carbon monoxide content is regulated by the mixture adjustment screw with the restrictive cap removed.
Adjusting the idle speed using gas analyzing equipment must be done in the following sequence on a warm engine with the restrictive cap removed:
1. First, use the idle speed adjustment screw to set the minimum crankshaft speed at idle.
2. Set the mixture adjustment screw to a position that ensures the CO content in the exhaust gases is within 0.5-1.0%.
3. Finally set the idle speed adjustment screw to low idle speed.
4. Check the content of CO and CH in the exhaust gases, which should not exceed: at the minimum crankshaft speed - 1.5% and 1200 ppm, respectively,
at an increased rotation speed of 2400 rpm - 2% and 600 ppm, respectively.
5. Install a new limit cap.
If it is impossible to achieve the specified indicators for the content of CO and CH in the exhaust gases, it is necessary to diagnose the engine and its systems, eliminate malfunctions and repeat the adjustment.