The situation when you turn the ignition key, the starter cheerfully turns the crankshaft, but the car instead of confident start produces only convulsive claps, is familiar to many motorists. The engine sneezes and doesn't start. This is a sure sign that the cylinders are a violation of the combustion process of the fuel-air mixture. Cottons can be distributed either into the intake manifold (back claps), or fly into the exhaust system, scaring the owner with loud shots.
Such symptoms cannot be ignored, as they indicate a critical failure in the operation of one of the main life support systems of the car. Most often, the problem lies in the wrong moment of ignition, interruptions in spark formation or violation of the proportions of the mixture. Fuel injection It can occur too early or too late in the compression stroke, which leads to ignition outside the combustion chamber.
For successful diagnosis, you will need not only the desire to fix the car, but also a basic understanding of the principles of the internal combustion engine. In this article, we will discuss the main reasons why a car shoots a muffler or carburetor, and propose a fault-finding algorithm. Proper identification of the source of the problem will save you time and money to replace the repaired parts.
Physics of the process: why cotton happens
To understand how to eliminate the malfunction, you need to understand the mechanics of what is happening. In a serviceable internal combustion engine, the mixture of air and fuel is ignited from the spark strictly at a certain point when the piston is at the top dead point. If spark-point knocked down, the mixture may burn up when the intake or exhaust valves are still open.
When the mixture is ignited at the time of opening the intake valve, cotton is fired into the intake manifold. This phenomenon is often accompanied by the ejection of flames from the air intake. If the combustion occurs at the stroke of release or the mixture burns out already in the exhaust tract, you hear a loud shot from the silencer. Cotton occurs due to the ignition of the mixture at the moment when the valve is open..
The main culprits of this engine behavior are:
- 🔥 Downed phases of gas distribution due to the jump of the belt of the GRM.
- ⚡ Incorrectly exposed ignition or sensor malfunction.
- 💧 Getting water or poor-quality fuel into the cylinders.
Diagnosis should begin with determining where exactly the engine sneezes. If the sound comes from the air filter - the problem is intake, if the rear of the car - in the release. This is the first and most important partition to narrow the search circle.
Listen to the nature of the sound: a deaf pop often indicates a rich mixture, and a loud, sharp shot indicates a late ignition or poor mixture.
Problems in the ignition system: spark and timing
The ignition system is the heart of the ignition process. If the spark slips at the wrong moment or has insufficient power, the fuel does not burn completely and burns up in the pipe. On cars with trampler The cause is often the displacement of the lid or wear of the runner. In modern electronically controlled systems (ESUD), timing is responsible for crank-point (DPCV).
If the DPC gives an incorrect signal or has a backlash, the control unit receives distorted data on the position of the pistons. As a result, the spark is served either too early or too late. It is also worth checking the high-voltage wires and coils. Breakdown of the insulation can lead to the fact that the spark goes to the mass or jumps to the neighboring cylinder in the wrong stroke.
Pay attention to the condition of the candles. Turn them around and look at the color of the garlic:
- 🔴 Red plaque - the use of additives with metals, possible ignition skips.
- ⚫ Black dry soda is a rich mixture, fuel overconsumption is possible.
- ⚪ White plaque - poor mixture or overheating, the risk of burnout valves.
☑️ Checking of the ignition system
It is important to check the gaps between the electrodes of the candles. Too much clearance requires increased voltage for breakdown, which the coil may not provide under load. Switch On older systems, it can also malfunction by passing impulses or forming them with a delay.
Failures in the power system: mixture and nozzles
The second main reason why the engine sneezes and does not start is a violation of the preparation of the fuel-air mixture. If the mixture is too rich (a lot of gasoline, not enough air), it does not have time to burn in the cylinder and burns out in the exhaust manifold, causing cotton. This often happens when there is a fault. fuel-pressure regulator Or "spouting" nozzles.
In carburetor cars, the needle valve and the level of fuel in the float chamber are responsible for this. If the valve does not hold, the gasoline is poured and the candles are poured. In injection systems, the culprit may be air-flower (DMRV) which transmits incorrect data on the amount of incoming oxygen. The control unit, receiving false signals, pours excess fuel.
Symptoms of nutritional problems:
- 💨 Black smoke from the exhaust pipe when trying to start.
- 🛢 The smell of unburned gasoline after unsuccessful start attempts.
- 📉 Fuel-filled spark plugs.
How to check the nozzles without a stand?
You can remove the fuel ramp and connect it to the battery through a button (observing safety precautions!). When supplying power, the nozzle should issue a clear click and spray the fuel with a cone, rather than pouring a jet.
It is also worth checking the idle valve and the idle regulator. If they are contaminated or jammed, the engine may stall immediately after starting or "sneeze" when trying to add gas. The intake system should be sealed: the pumping of unaccounted air also leads to impoverishment of the mixture and unstable operation.
Mechanical malfunctions and phases of HRM
The most serious and expensive option is a violation of the gas distribution phases. If the belt or the HRM chain jumped even on one tooth, the valves begin to open and close out of time with the pistons. The intake valve can open when the cylinder is still burning or exhaust gases, which causes a powerful cotton in the intake.
This is often accompanied by loss of compression. A compression check is a mandatory diagnostic step if the electrics and fuel are in order. Low compression in one or more cylinders indicates burnout of valves, rings or damage to the gasket of the HBC. Hydrocompensators They can also affect the gaps, but more often they just make noise.
Comparative table of symptoms:
| Symptoms. | Probable cause | Where's the cotton? |
|---|---|---|
| Shoots at the silencer | Late ignition, rich mix | Release |
| Cotton to carburettor/air | Early ignition, poor mix | Inlet |
| Engine troit | Absence of spark in cylinder | Both paths |
| Metal thumping | Pistons hitting the valves | Cylinder block |
The GRM belt jump is a critical malfunction. Attempts to start the engine can lead to a meeting of valves with pistons and overhaul of the engine.
Diagnosis on carburetor and injector cars
Diagnostic approaches vary depending on the type of fuel supply system. The old ones. carburetor The problem often lies in mechanics: the angle of ignition ahead is set by the turn of the trambler, and the composition of the mixture is regulated by the jeeklers and the level in the float chamber. There are frequent problems with a vacuum corrector or centrifugal regulator.
In injection systems, everything is electronically controlled. If the engine sneezes, the first thing to do is to count the error codes through the OBD-II diagnostic connector. Even if the Check Engine light bulb does not burn, errors on oxygen sensors, DPCs or DPRVs can be stored in memory. Electronic control unit (ECU) can go into emergency mode, ignoring the readings of sensors and using tabular values, which leads to incorrect operation.
Algorithm for the injector:
- Counting errors as scanners.
- Check the pressure in the fuel ramp (manometer to help).
- Check the spark and condition of the candles.
- Check the inlet for air suction.
We should not forget about the quality of the fuel. Water in the tank or a low octane number of gasoline can cause detonation and cotton. Water, once in the cylinder, does not burn, but turns into steam, disrupting the combustion process and potentially causing a hydraulic shock.
Remediation and prevention
Removal of the fault depends on the cause found. If the problem is in ignition - replace candles, wires, trambler cover or sensors. For carburetor cars, you may need to adjust the angle of ignition advance using a strobescope. Angle of advance It must strictly comply with the manufacturer's specification for the fuel octane number.
If the mixture is to blame - wash the nozzles, replace the fuel filter, check the pressure regulator. In the carburetor, clean the jellyplates and blow the channels with compressed air. In case of suspicion of GRM - open the protective cover and check the marks. This is a time-consuming procedure, but it will save you from more serious expenses.
⚠️ Warning: If after replacing the belt, the engine started shooting, immediately silence it! Most likely, the labels are incorrectly exposed, and further work will lead to the destruction of the engine.
Prevention of such problems includes regular replacement of candles and filters, use of high-quality fuel and timely diagnostics of electronic systems. Don’t ignore floating idle or increased fuel consumption – these are the first bells.
Use the Quick Start spray (ether) only to check the launch. If the engine starts only with ether and stalls - the problem is precisely in the supply of fuel (gasoline pump, filter, injectors).
Frequently Asked Questions (FAQ)
Why does the engine shoot at the muffler at start-up?
This is often a sign of too late ignition or a rich mixture. The fuel does not have time to burn in the cylinder and burns in the exhaust manifold, causing cotton. The reason may also be the failure of the ignition in one of the cylinders.
Can I drive if the car sneezes but starts?
It's highly discouraged. Prolonged operation of the engine with cotton can lead to burnout of the valves, destruction of the catalyst or even damage to the air filter (when cottoning into the intake). It is better to diagnose the problem on the spot.
Does the water in gasoline affect the engine clap?
The water does not burn and disrupts the combustion process. Getting into the cylinder, it causes interruptions in work, tripling and can provoke cotton due to unstable ignition of the main mass of fuel.
What if cotton has appeared after replacing the belt?
The engine must be stopped immediately. Most likely, the belt is installed on the labels incorrectly (hit at least one tooth). Requires opening and re-installation of the shaft marks.