Engine. ZMZ-402, which is one of the most massive power plants in the post-Soviet space, is still found on a huge number of cars. GAZelle, Volga And it's also a vehicle that's simple, but it's a very maintenance-intensive engine, and the power system is the key, and not only is the carburetor being adjusted properly, but it's also a way to keep the power unit running smoothly in all modes.
Many owners are faced with the fact that after the wrong setting, the engine begins to "sneeze", stop idling or, conversely, consume excessive amounts of gasoline. carburetor This is a complex mechanical device where the slightest deviation in the positions of the jelly or throttle valves leads to impaired mixture formation. In this article, we will discuss the adjustment process in detail, based on technical regulations and practical experience.
Before you can get your tools, you need to make sure that the adjacent systems are working properly, and it's useless to adjust the fuel supply if the cylinders are getting untreated air or the spark is slipping irregularly. Tightness The first condition of the inlet tract is that without which all further actions will be meaningless, and only a comprehensive approach will allow you to achieve the perfect operation of the engine.
Preparation of the engine for setting
Start work should only be when the engine is heated to the operating temperature, which is approximately 80-90 degrees CelsiusThe cold engine has different heat gaps and fuel evaporation specifications, so setting the "cold" will lead to errors in real operation. Make sure the ignition system is set up correctly and the gaps in the valves are exposed according to the specification.
Visually inspect all the carburetor and intake manifold connections. The foreign air pump is a frequent cause of unstable work that cannot be eliminated by adjusting screws. Check the condition of the air filter: if it is clogged with dust, the mixture will be overenriched, and you will disrupt the settings, trying to compensate for the lack of air.
Before starting the adjustment, make sure that the throttle drive cable has a free ride and does not snag in the shell, otherwise accurate idling adjustment will be impossible.
A good diagnosis will require a tachometer and, preferably, a gas analyzer, although experienced craftsmen often do away with hearing, but relying on hearing alone is risky, since the human ear may not notice changes in the composition of the mixture that affect the economy and toxicity of the exhaust. Instrumental control It gives objective data.
⚠️ Warning: Never adjust in a closed garage without running exhaust ventilation, and combustion products, especially carbon monoxide, are odorless and deadly when inhaled in a confined space.
Adjustment of the idling system
The idling system is what most often begin to set up owners of cars with an engine ZMZ-402This is the mode in which the engine runs most of the time in the urban cycle, and the main objective here is to achieve minimum fuel consumption at stable speeds and minimal exhaust toxicity.
The tuning process is done by two screws: a quantity screw and a mixture quality screw. First, the quantity screw sets the approximate revolutions, then the quality screw finds the position of the maximum rotational frequency, then adjusts the number of revolutions to normal again, this operation is repeated several times until you get a stable result.
☑️ Algorithm of setting XXX
It is important not to twist the screw quality of the mixture. Excessive twisting leads to impoverishment of the mixture, which causes engine overheating and burn of valves, and excessive twisting - to overuse of fuel and "throwing" candles. Optimal position It is usually in the range of 2-3 rpm from a fully swirling state, but the exact value depends on the wear of the engine.
- 🔧 The quality screw regulates the composition of the mixture at idle.
- ⚙️ The screw of quantity opens the throttle at a fixed angle.
- 📉 Normal idling speeds for ZMZ-402 are 700-800 rpm.
- 📈 A sharp opening of the throttle should not cause failures of turns.
If after all the manipulations the engine continues to work unstable, it is worth checking the tightness of the gasket under the carburetor. It often happens that a microcrack in the textolite depositor or the gasket itself negates all the adjustment efforts. Air suction In this zone, the mixture is too poor in one cylinder, causing trifling.
Adjustment of transition modes and acceleration pump
One of the most common engine problems ZMZ-402 This is a power failure when you push the gas pedal abruptly, and this is directly related to the accelerator pump, which is supposed to instantly enrich the mixture when the throttle is opened, and if the jet of gasoline is weak or intermittent, the acceleration dynamics suffer.
To check the pump, remove the air filter, press the throttle lever sharply, and look into the diffuser. You should see two clear streams of gasoline coming from the sprayers. If the jet is sluggish or not, you should take the carburetor apart and check the integrity of the aperture pump and the purity of the channels.
Frequent causes of failures in acceleration
The most common problem is the wear of the nozzle of the accelerator pump or the clogging of the return valve, and it is also worth checking the free stroke of the pump drive lever - if it is chosen completely, the injection will begin late.
It is also important to pay attention to the work. economiser This assembly cuts off the fuel supply when the engine is braking, but must open completely when loaded. A malfunction of the electromagnetic valve or control unit can cause the engine to stall when the gas is discharged or, conversely, not develop full power.
When adjusting transients, keep an eye on the smoothness of the throttle. There should be no jamming. The throttle axis may eventually develop a landing position, leading to air suction, and in such cases, the carburetor needs to be replaced or seriously restored, because adjustments cannot fix the defect.
Table of regulatory parameters of the carburetor
To properly adjust, you need to rely on factory data. Below are the main parameters that must be observed when adjusting carburetors series K-151 Deviations from these values are allowed only within the limits that compensate for engine wear.
| Parameter | Normative value | Permissible deviation |
|---|---|---|
| Idle turn | 750 ± 50 rpm | ± 50 rpm |
| CO content at XX | 1.5 - 2.0 % | ± 0.5 % |
| Fuel level in the float chamber | 24.0 mm | ± 2.0 mm |
| Progress of accelerator pump diaphragm | 1.4 mm | ± 0.2 mm |
It is worth noting that the data in the table is relevant for a serviceable engine, if the engine has low compression or disrupted gas distribution phases, trying to set the parameters strictly on the table can lead to unstable operation. regulation It is compensatory and requires an individual approach.
Strict adherence to the fuel level in the float chamber is the key to the correct operation of all carburetor dosing systems, from idling to maximum capacity.
Typical malfunctions and methods of their elimination
Drivers often experience specific symptoms during operation that indicate that intervention is needed, such as floating idling speeds that indicate a drive cable or a malfunction of the EPHC system. It is important to be able to diagnose the problem by external signs.
If the engine is idling, but aligns with the addition of gas, it is most likely the problem with the ignition system, not the carburetor. However, if the tripping is accompanied by claps into the muffler, this is a sure sign of over-enrichment of the mixture or skipping the ignition in a particular cylinder. Diagnostics It has to be consistent.
- 🚗 « Cotton in a carburetor is too poor mixture or early ignition.
- 💨 Black smoke from the exhaust - enrichment of the mixture, checking the fuel level.
- 📉 The engine stalls when braking - a malfunction of the economiser or air sucker.
- 🔥 Overheating of the engine is too poor mixture, check the jelly.
A common problem with older carburetors is the wear and tear of the throttle and its axes. The throttle starts to dangle, letting in excess air, which makes the mixture uncontrollably poor. Visually, you can see this from the characteristic swell around the damper. The solution is one: replacing the knot or carburetor assembly, because the swelling and sling of the axles at home rarely produce long-lasting results.
⚠️ Note: When disassembling a carburetor, it is strictly forbidden to use a metal tool to clean the jellyclera. Even a microscopic scratch will change the throughput of the jellyclera, and it will be impossible to restore factory parameters.
Nutrition maintenance and prevention
Adjusting the carburetor is only part of the maintenance, for a long and reliable engine. ZMZ-402 You need to change your fuel filters regularly and drain the sludge from the sludge filter, and when you get into the carburetor, you can quickly disable the needle valve and clog the sludge.
Once a year, it is recommended to wash the carburetor completely in an ultrasonic bath or with special chemical compositions, which allows you to remove lacquer deposits that form from the lighter fractions of gasoline and interfere with the normal operation of the valves. A clean carburetor is easier to adjust, and it keeps the parameters more stable.
Remember to check the condition of the gaskets. Every time you disassemble the gasket under the base of the carburetor and between the body and the lid, it is better to replace it with new ones. The use of a sealant is permissible only in extreme cases and only a special heat-resistant type that is not dissolved with gasoline. Tightness Connections are the basis of security.
The Secret of Durability
Installation of an additional filter of fine fuel cleaning in front of the carburetor (transparent bulb) allows you to visually monitor the purity of gasoline and notice the ingress of water or dirt in time, saving the jellyfish from clogging.
Impact of Fuel Quality on Settings
The quality of gasoline at domestic gas stations can vary significantly, which directly affects the work of the carburetor. Low octane number causes detonation, which the driver may mistaken for a malfunction of the ignition or power system. ZMZ-402 It is designed for gasoline A-76 (the old GOST) or AI-80, but modern environmental requirements and wear of engines dictate their adjustments.
If you use fuel with an octane number above the estimated, you may need a slight adjustment of the angle of advance of ignition, but the carburetor usually does not need this. However, if there is a lot of alcohol or other additives in gasoline, you may need to replace rubber seals with more persistent ones, since aggressive chemistry destroys standard rubber.
The poor mixture burns more slowly and at higher temperatures, leading to overheating of exhaust valves and pistons. The savings of a liter of gasoline can result in expensive engine overhauls.
FAQ: Frequently asked questions
Why does the carburetor “shift” and what is the reason for black soda on candles?
The main cause of overflow is leaky needle valve float chamber or improperly exposed fuel level, also possible catch float, black lobe indicates work on too rich mixture, which requires checking the jigs and idling system.
Can the carburetor be adjusted without a gas analyzer?
Yes, experienced mechanics adjust the candles by ear and color, twisting them after a test run, but without the devices it is difficult to achieve the optimal balance of economy and environmental friendliness, so for the initial adjustment it is better to use at least a simple tachometer and a table of norms.
How often should the carburetor be adjusted on the ZMZ-402 engine?
When using quality fuel and a proper ignition system, the carburetor requires adjustment no more than once a year or during seasonal maintenance. Frequent adjustments indicate a malfunction in the engine or the carburetor itself.
Should I put remakes on an old carburetor or is it easier to replace the node?
If the carburetor body does not have deformations and wear of the axes of the valves, a quality remix can prolong its life. However, if the mileage is high, it is often cheaper and more reliable to purchase a new carburetor or carburetor from the recovery plant, since the production of seats with the remplekt is not eliminated.