The situation when the car starts without problems after parking, but refuses to “grab” after night downtime, is familiar to many owners. This is a classic symptom that the engine control or fuel supply system is operating with errors at low temperatures of the nodes. Cold launch. This is a high load mode that requires an accurate ratio of air and fuel.
If there are no problems on the heated engine, then the main mechanical components, such as the starter and the battery, are most likely to be in good working order. However, you can not ignore the problem, since over time, a difficult start-up can develop into a complete inability to start the engine at any time of the day.
In this article, we will discuss in detail why the car behaves capriciously after cooling down, which systems require inspection in the first place and how to conduct initial diagnosis on your own. Timely detection of malfunction This will help to avoid costly repairs in the future.
Impact of fuel quality and supply system
The first thing to look out for when having a launch problem is the state of the fuel system. Often the reason lies in the low-grade gasoline or a diesel that contains impurities or water. Water in the tank at negative temperatures can freeze, blocking the fuel intake or damaging the system elements.
Particular attention should be paid to the work of the fuel pump. If it is worn out, it may not create enough. ramp pressure Right after the ignition is activated. On a hot engine, the fuel is already in the system, and the residual pressure is enough to start, and on a cold pump should work perfectly.
How to check the pressure in the fuel ramp?
A pressure gauge will be required to check. He's being hooked up to the ramp. When ignition is turned on, the pressure should rise to the value specified by the manufacturer (usually 3-4 atmospheres) and last for a long time. If the pressure drops immediately after the pump is turned off, the nozzles or pressure regulator are defective.
The cause may also be contaminated. fuel-nozzle. The coar on the sprayers violates the injection torch, and the fuel does not have time to evaporate in the cold intake manifold. This leads to over-enrichment or, conversely, impoverishment of the mixture at the time of start.
Do not forget about the filter of fine fuel purification. If it is clogged with dirt, the throughput falls and the pump takes time to pump the right amount of fuel. In the cold, the viscosity of the fuel increases, exacerbating the problem.
Use only certified fuel additives to clean the system, but remember that they are only effective in the early stages of contamination. Strongly clogged nozzles are cleaned only on the stand.
Problems with the ignition system and candles
The ignition system is the second candidate for testing. Ignition candles have their own resource, and when it is exhausted, the spark becomes weak or unstable. On a cold engine, when the richer mixture is richer, a powerful spark is required to ignite. If candlelight broken or electrodes burned out, ignition does not occur.
It is also important to check high-voltage wires and ignition coils. At low temperatures, the insulation of the wires becomes stiffer and may crack, causing breakdown. Visually, this can be seen in the dark: if the “dancing” sparks skip under the hood, the wires are subject to replacement.
- 🔌 Electrode-stained garment: indicates improper combustion or wear of the candle.
- 💧 condensate: moisture inside the coil or tip can block the spark only on the cold.
- 📉 Reduced compression: Old candles may miss a spark in a compression stroke worse.
Ignition coils are also prone to microcracks of the body. When heated, the material expands and the crack “tightens up,” restoring contact. On the cold through the crack, a current leak may occur, because of which the spark does not reach the candle. Testing the coils for resistance often does not give a result, so they are changed by exclusion or checked on an oscilloscope.
Sensors and Electronics: The Role of Temperature
The modern engine is controlled by electronics, which relies on sensor readings. The key element here is coolant (DG). If it sends the wrong signal that the engine is warm, the ECU will not enrich the cold start mixture, and the machine will not start.
The throttle position sensor (DPD) can also fail. When starting, the damper must be closed, and if the ECU "sees" an open throttle, it may block the launch or supply the wrong amount of air. Memory errors electronic control unit (ECU) can persist and affect the operation of the motor.
Another important element is the mass air flow sensor (MADR). If it is contaminated or defective, the calculation of the fuel-air mixture will be incorrect. The hot engine works according to other algorithms and can compensate for the error, and on the cold engine it stalls or does not catch.
⚠️ Note: When diagnosing electronics, don’t rely on the absence of a burning Check Engine lamp. Many sensor malfunctions (e.g., TTZ) may not be recorded as critical errors in memory, but may affect engine performance.
The sensors are checked using a multimeter and a diagnostic scanner. It is necessary to compare the readings with reference values for a specific temperature. Often, the problem is solved by simply replacing an inexpensive sensor, which returns the car to a stable start.
Mechanical Causes and Compression
If the electrics and fuel are fine, it is worth thinking about the mechanics. Low. compression A common cause of problems with cold start. When the engine cools, the gaps between the piston rings and cylinder walls increase, and if the wear is high, the pressure drops below the critical level.
On a hot engine, the metal expands, the gaps decrease, and the compression is temporarily restored, allowing the motor to start. This is a sure sign that the engine life is coming to an end and is required. overhaul Or a piston group replacement.
It is also worth checking the phases of gas distribution. If the GRM belt is stretched or jumped on the tooth, the valves will open in a wrong time. This disrupts the process of filling the cylinders and exhausting gases. The cold engine may simply not start due to the lack of compression at the right time.
| Symptoms. | Possible cause | Method of verification |
|---|---|---|
| Engine sneezes | Problems with GRM or candles | Label check, candle replacement |
| Starter's sluggish | Low compression or ACB | Compression measurement, load on the battery |
| Launch with gas only | Failure of RXX or DPA | Scanner diagnostics |
| Launch after a long torsion | Pressure drop in the ramp | Manometer in the fuel system |
Mechanical problems often occur at low temperatures due to changes in thermal gaps. If the hot car goes normally, but the cold does not start - first of all measure the compression.
Idle adjustment and throttle
Throttle and idle regulator (RX) contamination is one of the most common causes of unstable start-ups. Nagar formed on the edges of the valve, prevents it from closing tightly or, conversely, covers the channel completely. The ECU cannot properly regulate the air supply at the start.
An idle regulator is a stepper motor that pushes the rod, opening the channel to air at start-up. If the rod is jammed from dirt or wear, the necessary amount of air to create a mixture does not arrive. After heating, the valve is opened, and the problem disappears.
Cleaning the throttle often solves the problem. After cleaning, many modern cars are required. throttle-drive through a diagnostic scanner or a special pedaling procedure. Without this, the revs can float and the launch remains unstable.
☑️ Throttle node diagnostics
Effects of oil and viscosity of lubricants
Motor oil plays a critical role in cold start. If the viscosity of the oil does not correspond to climatic conditions (for example, thick oil is poured). 10W-40 or 15W-40 In severe frost, the starter is physically difficult to turn the crankshaft. The hot oil becomes thinner, and the start is easy.
In addition, old, lost oil can create excessive resistance. It is important to use synthetic oils with index low-temperature (first digit before W) corresponding to your region. For winter, the best oils are 0W-30 or 5W-30.
It is also worth checking the status of the starter. If the starter sleeves are worn out, the anchor may be wedged. On cold, when the metal is compressed, the wedge is stronger. When heated from the engine, the bushings expand, and the starter begins to work normally.
⚠️ Warning: Do not try to start the engine "from the pusher" or on the cable if you suspect problems with lubrication or mechanics. This can lead to a break in the belt timing and serious damage to the engine.
Specificity of diesel engines
If you have a diesel car, the reasons may be different. The main one is a malfunction. lamp-light. They heat up the combustion chamber before launch. If one or more candles do not work, the fuel in the cold cylinder cannot be ignited.
The second important point is the serviceability of the TNVD (high pressure fuel pump) and injectors. Diesel fuel is paraffinized at low temperatures. If the tank has summer fuel or water, by morning a jelly-like mass is formed, which does not pass through the filters. The hot paraffin dissolves and the car starts.
Compression in diesel is critical. To ignite the diesel fuel, the temperature in the cylinder should reach 700-900 degrees due to compression. If the compression has fallen in at least one cylinder, the cold engine will not start. On the hot due to the expansion of the pistons, the compression increases, allowing the motor to work.
Why does diesel smoke when starting cold?
White smoke when starting on a cold one often indicates that the fuel does not burn completely due to the low temperature in the cylinder (incandescent candles are defective) or the entry of antifreeze into the combustion chamber.
Frequent Questions and Answers (FAQ)
Why does the car start and immediately stop in the cold?
Most likely, the problem is in the idle regulator or the sucking of unaccounted air. The ECU does not have time to adjust the mixture, and the engine stalls. The temperature sensor may also be defective.
Can the pump work intermittently (periodically)?
Yes, the electric motor of the gas pump may have worn brushes or contacts. Cold contact can disappear, and from vibration or heating to recover. This is a common cause of “floating” malfunction.
How does frost affect engine start-up?
Frost increases the viscosity of the oil, reducing the return of the battery and increasing the resistance of scrolling. It also condenses moisture in the exhaust system and tank, which can block the start.
Do I need to warm up the car before the trip?
Modern engines do not require long warming up in place. It is enough 1-2 minutes for the oil to enter the working mode, after which you can start moving in a gentle mode. Prolonged warming up on the spot is harmful to the engine.