Causes of poor starting of an injection engine

The injector design, thanks to the computer and various sensors, is more complex, and therefore there are more vulnerable links in such an engine compared to a carburetor engine. It is more difficult to find the source of the problem. It happens that a car with an injector starts poorly or does not start at all (if the carburetor does not start, and also if the diesel engine does not start). What, in this case, needs to be checked first?

GASOLINE PUMP

A functioning fuel pump produces a characteristic sound. If there is a suspicion that it is faulty, then this suspicion can be confirmed or refuted by checking the spark plugs: if they are dry, then the problem is in the fuel pump. What has failed in the fuel pump - wires, fuse or relay - remains to be determined. How to check the fuel pump

First, we check the integrity of the wires going to the fuel pump to see if they are oxidized. To do this, other, new wires need to be connected directly from the battery to the fuel pump. If the fuel pump works normally with them, then you need to change the standard wires.

If everything is in good condition - the fuse, relay and fuel pump wires, but the latter nevertheless does not work, we can only conclude that the fuel pump itself has become unusable and requires replacement (replacing the fuel pump on a VAZ). Again, to check the serviceability of the fuel pump, you need to connect it to the battery directly, or, instead, connect a working fuel pump.

Video: VAZ 2110 fuel pump (injector) does not work, looking for the reason

RAIL PRESSURE

It happens that the injector does not start due to the lack of sufficient pressure in the fuel rail (normally, it should not fall below 2.8 kg/cm²). This can happen if the fuel pressure regulator is malfunctioning.

A dirty fuel filter also prevents normal pressure in the fuel rail. It is better to change the fuel and air filters more often.

CRANKSHAFT SENSOR

This is the only sensor, if it is faulty the engine will not start at all. If any other sensors malfunction, the performance of the injection engine only worsens. How to check the crankshaft sensor

INJECTORS

As you know, injectors become unusable one at a time, and nothing bad will happen to the engine if only one injector does not function. It may be worse (there will be tripping), but the engine will work.

To identify a faulty injector, you need to start the engine and touch the exhaust manifold pipes. The pipe that turns out to be colder than the others will indicate the cylinder that is not working. By the way, the cylinder may not work not only due to the fault of the injector, but also due to the fault of a failed spark plug. In this regard, if a faulty cylinder is identified, its spark plug needs to be checked.

IGNITION SYSTEM

In an injection engine, you need to check the ignition module and spark plugs.

If an injection engine does not start, the cause may be an unregulated ignition. There is a very simple way to install the ignition.

GAS DISTRIBUTION SYSTEM

Unadjusted valves in themselves, as a rule, are not the reason that the engine does not start at all. If the valve clearances are wrong, the engine will start, but it will simply run worse. Unadjusted valves can pose a serious problem for starting the engine, in combination with some other malfunction. If there is not one problem, but several (including incorrect valve clearances), then the engine may not start. So adjusting the valve clearances can help fix this problem (how to adjust valves).

Also, the engine will not start if an error was made when installing the timing belt (how to set the timing marks).

Perhaps these articles can also help you solve the problem:

Video: Why a fuel-injected car won’t start

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Modern cars are gradually moving from the concept of mechanisms to the concept of organisms. This is a highly complex system that requires ideal operating conditions. High engine power, squeezing everything that can be squeezed out of technology, and other features of the modern automobile industry indicate that modern cars must receive maximum care in order to work for a long time. One of the common problems that arise from improper car care is poor engine starting after it warms up. This means that if you park for a few minutes near the store, you will not be able to start the engine properly. The problem lies in two possible types of breakdowns, but there are also extraordinary cases. Today we will deal with the most common problems in this case, and also talk about specific types of problems.

It should be noted that the symptoms of poor hot starting can manifest themselves in different ways. One car refuses to start at all until the engine cools down a certain amount. Another power unit starts only on the third or fourth try, and the third one simply has to be cranked for a long time to start. In any case, no matter what happens to your car in this context, you need to find the problem and be sure to fix it. This task is a harbinger of more serious breakdowns, the repair of which will cost you much more money. So let's figure out why the car doesn't start well when it's hot.

The main reasons for poor starting

The list of reasons why a cold engine is difficult to start is quite wide. Before starting diagnostics, it is necessary to more accurately localize the fault. Make sure that the starter is charged and turns the engine smoothly (at the same speed). Additionally, it is worth excluding the possibility of refueling with low-grade gasoline.

Fuel supply

Problems with starting the engine can arise both as a result of the fact that there is no fuel supply, and due to failures in the process of its ignition in the engine cylinders. As for the fuel supply, there may be too little fuel to start. It is also possible that the spark plugs are flooded with excess fuel.

1. It's worth starting the check by making sure there is an exhaust. If light smoke appears from the exhaust pipe after turning the starter, then this indicates that there is fuel supply to the cylinders.
2. The next step is to remove the spark plugs. The spark plugs must be unscrewed after an unsuccessful attempt to start the engine. If the spark plug is flooded with gasoline, then this can often indicate problems with injector sealing or ignition. Check the integrity of the spark plugs themselves and the high-voltage wires, and also make sure that there is a spark at the spark plugs. A dry spark plug will indicate that fuel is not being supplied to the cylinder.
3. Clogged coarse and fine filters, as well as faulty or heavily coked filters, can also hinder the normal supply of fuel to the engine. Fuel may also not flow into the engine due to a sudden failure. This means that the fuel pump is not creating the required pressure. To find out the reasons, you will need to check the fuel pressure in the rail and the fuel pump itself.

An additional nuance may be air leaks in the fuel system. It is necessary to examine the lines for damage, bends, cracks, etc. Gasoline leakage is a clear sign of loss of seal in the fuel lines.

Electronic sensors

The electronic injection system is equipped with special sensors, thanks to which interaction with the engine is realized. Failure of individual electronic components can result in incorrect signals being sent to the control unit and the engine cannot be started.

If the engine does not start, then you need to check several sensors:

• (DPRV);
• throttle position sensor (TPS);
• (DFID);

It is also necessary to simultaneously clean the throttle, check the air filter and the XX valve. Self-diagnosis of sensors can be done using a multimeter.

Ignition check

The engine may not start if the ignition distributor is faulty. This malfunction manifests itself in such a way that when the starter rotates, the so-called seizure does not occur, that is, there are no signs of single attempts to ignite the fuel-air mixture in the engine cylinders.

It is also worth paying attention to the belt and its drive. In some cases, it is worth checking the condition of the variable valve timing system (if equipped). The ignition coil can be checked using a multimeter.

Compression reduction

A loss of compression in one or more engine cylinders is a consequence of natural wear or damage to the power unit. A motor with low compression does not, as there is a strong increase in the gaps between the parts in the cylinder. In other words, it is not possible to achieve the required pressure in the combustion chamber to ignite the working mixture at the time of start-up.

Frequent causes of this malfunction may be piston destruction, broken or stuck piston rings, timing belt burnout, wear of the cylinder walls, etc. Low compression most often appears during a cold start, but can also be present constantly (when trying to start a very worn engine “hot”). An engine with such a malfunction is most difficult to start at low temperatures. For an accurate diagnosis, compression must be measured.

Reasons for improper operation of an injection engine

There may be several reasons why an injection engine does not start well when cold. The main one is sensor malfunction

. If one of the modules breaks down, the electronic control unit receives incorrect data, causing the engine to start poorly and run intermittently.

Common causes of poor starting of an injection engine.

Air leak

Occurs when there is a leak in parts of the air supply system. The mass flow sensor cannot catch some of the air entering the engine, which is why a lean mixture is supplied to the combustion chamber. This leads to unstable idling and a problem with cold starting of an injection engine.

During warm-up or choke operation, this problem is almost unnoticeable, but when the engine warms up to operating temperature, interruptions in idling become more noticeable.

Air leaks can occur for the following reasons:

• violation of the sealed connection in the vacuum booster;
• mechanical damage to the fasteners and air supply hose to the intake manifold, pressure regulator pipelines and crankcase ventilation system;
• Damage to the gaskets between the cylinder block and the intake manifold.

The cause of air leaks can be determined by visual inspection. If the malfunction significantly affects the idle operation and starting of a cold injection engine, before repairs are performed, you can increase the speed by disconnecting the plug from the mass flow sensor. This action will lead to a significant increase in fuel consumption, so it is not recommended to delay repairs.

If the suction is slight, it is enough to adjust the fuel supply using the L-probe device.

Main indicators of the fuel and air mixture

Mass flow sensor malfunction

Incorrect operation or breakdown of the sensor leads to an immediate stop of the motor after starting. When this happens, you need to disconnect the sensor and start the car again. If the engine runs without interruption, then the flow sensor needs to be replaced.

Temperature sensor faulty

When the central control unit does not receive signals from the coolant temperature module, it takes the value zero. The built-in program prepares the working mixture according to this temperature, which leads to the following consequences:

• injector engine does not start well when cold;
• detonation at low speeds.

The module cannot be repaired, so the faulty part is replaced with a new one.

Ignition faulty

The problem can be corrected by setting the timing of the spark, adjusting the position of the timing belt and replacing damaged parts.

Table of indicators of temperature sensor resistance versus coolant temperature.

A breakdown in the fuel regulator leads to fuel leakage into the combustion chamber through the intake manifold pipes. As a result, an enriched mixture enters the engine, which leads to severe clogging of the spark plugs. This malfunction significantly affects the cold start of an injection-type engine.

Camshaft timing sensor

A breakdown leads to the transition of the fuel supply mechanism to emergency mode, in which the injector supplies fuel twice as much as necessary.

Reasons for replacing the module:

• difficult starting;
• interruptions in the vehicle’s self-diagnosis system;
• significant increase in fuel consumption;
• smoking in the exhaust gas release mechanism.
• difficult cold start of an injection engine

You can correct the problem by adjusting the position of the sensor yourself or by contacting a service center.

Stepper motor.

The malfunction of this element does not allow maintaining idle speed (the engine does not have enough air). Driving the car is possible if you maintain idle speed with the throttle pedal when removing the load. If you have a DST-2M or DST-8 tester, set the idle speed on a warm engine to 900 - 1000 rpm using a stepper motor (if it is still controlled). Remove the connector from the stepper motor.

In this state, you can safely drive a car without experiencing any difficulties if the temperature outside is down to -5˚. In cold weather down to -15˚, starting a cold engine will be difficult, but using the same throttle pedal you can warm up the engine (using the pedal like a choke in a carburetor). After -18˚, starting the engine will become problematic - it will be difficult to ensure the specified air flow when the system transitions from the start mode to the warm-up mode. The engine will stall, and after 2-3 such attempts the spark plugs will flood.

Air leak.

A leak in the air intake system after the mass flow sensor causes instability at idle. The mass flow sensor “does not see” part of the air entering the engine; accordingly, the system incorrectly calculates the fuel supply (little fuel - lean mixture). On a cold engine and a slight suction, this effect may not be noticed, but as it warms up, instability at idle becomes more and more obvious and can lead to engine stalling. The causes of suction can be:

Rupture (breakage of fastenings) of any of the hoses that have access to the intake manifold (from a small tube to the pressure regulator to large crankcase ventilation tubes);

Vacuum booster leakage;

Damage to the gasket between the intake manifold and the engine, etc. Basically, the causes of air leaks can be determined visually. If air leaks make it impossible for the engine to idle, remove the connector from the mass air flow sensor. In this case, the idle speed will increase, but the car will be able to get to its destination. If you also set the stepper motor to an acceptable idle position, then there will be less inconvenience in control when the car is moving. A slight suction in the air supply system may not lead to noticeable changes in the driving characteristics of a car equipped with systems with fuel supply control using an L-probe sensor, but engine efficiency will decrease.

Mass flow sensor malfunction.

This defect causes the car to stall after starting. If the engine stalls after starting and you don't know what's wrong, try starting the engine with the mass flow sensor connector removed. If the engine runs after this, then there is a high probability that the sensor has failed.

The temperature sensor is faulty.

At temperatures below -8°C the engine will not start. In warm weather, you can maintain idle speed after starting by lightly pressing the throttle pedal. In the reserve mode of system operation, if the temperature sensor fails, the coolant temperature value is set based on the engine operating time. Starting a hot engine if the temperature sensor fails will have its own difficulties.

Throttle valve assembly faulty

. A hot engine stalls after starting - there is no transition to idle mode. It helps to press the throttle valve immediately after starting the engine. You can bend the throttle closed position limiter tongue, but so that the throttle position sensor readings equal 0 when the pedal is released (checked by a tester).

Ignition faulty

. There are no recipes here other than replacing all faulty elements of the ignition system.

Fuel regulator faulty

. The fuel regulator is leaking, additional fuel enters the intake manifold through the air pipe, and the engine floods. In this situation, the tube should be removed from the intake manifold; the engine should run stably.

In this article we will try to find out why the car does not start when cold, when hot, or simply stalls after it warms up. What needs to be done to fix these problems, and we will also discuss other options for engine malfunction.

Poor quality fuel.

It happens that even at gas stations of well-known brands, you can fill up with low-quality fuel, and then bite your elbows because the car does not start or starts, but with difficulty. It is very difficult to determine this probability, since when you leave the gas station, the car is still running on the old fuel, and will work until new fuel enters all the fuel channels of the car.

Main types of low-quality fuel:

1. Contaminated fuel is fuel that contains various deposits. They contaminate fuel channels, wires and filters. As a result, gasoline pressure drops and the car does not start.
2. Low octane number. As a rule, with such fuel, the car starts cold the second or even the third time, you can hear how noisy the engine is, traction disappears, and detonation occurs. It is not recommended to start a car on such fuel; it is better to drain it immediately and fill it with high-quality fuel.

Hot engine won't start?

Another common problem, and happy owners of domestic models know about it firsthand - the car does not start when hot. Much has already been said about the poor performance of the fuel pump on VAZ models. This happens especially often in extreme heat and when standing in traffic jams for a long time.

But owners of cars with diesel and injection gasoline engines may also encounter trouble when the car does not start. The reasons why the engine starts poorly are equally varied:

1. The sensor that monitors the coolant temperature receives distorted information, which leads to incorrect supply of the combustible mixture.
2. The tightness of the fuel injectors is broken, as a result of which the fuel mixture is over-rich and the engine does not start.
3. In diesel engines, the injection pump (high pressure fuel pump) does not work properly. It is worth thinking about replacing the plunger pair or bushings.
4. It is recommended to check the operation of the crankshaft position and air flow sensors.
5. Check the idle speed and fuel line pressure regulators.
6. Poor condition of armored wires.
7. Incorrect operation of the ignition module.

Fuel pump malfunction

Another reason why a car has trouble starting when cold is a faulty fuel pump.

In order to check whether the fuel pump is working, you need to turn on the ignition, and you will hear a buzzing sound from the gas tank, it will last for several seconds. As soon as the fuel supply stops, the required amount will be pumped in and pressure will be created in the fuel rail. The pump will then automatically turn off.

If you do not hear a buzzing sound and the car does not start, then you need to check the serviceability of the fuel pump.

On modern cars, fuel filters are installed. They filter fuel from various unnecessary deposits or sand, of which there is a lot.

If the fuel filter becomes clogged, then the required pressure is not created in the rail, and it becomes very difficult to start the car. In this case, the mixture begins to flow into the engine leaner. Since the temperature in the cylinders is low, it is extremely difficult to ignite such a mixture. Hence the problem with cold starting of the engine.

Bottom line

In conclusion, it is worth adding that it is better to look for the reasons for poor starting of a cold engine as they become more complex. So, you should not check the timing belt or engine compression without making sure there is fuel in the gas tank and a charge in the battery.

By methodically considering all possible fault options, you can get to the true cause of a poor start, and, in most cases, fix it yourself.

Most modern cars are equipped with a fuel injection system. The system is installed only on gasoline engines. Despite the complexity of the design and high requirements for fuel quality, the injection engine has a number of advantages over the carburetor mechanism:

• automatic adjustment of the injection system depending on the load;
• quick engine start, increase in its dynamic performance;
• low emissions of harmful substances;
• saving fuel consumption due to dosed injection;
• does not require prolonged warming up during low temperature conditions;
• the ability to program the electronic control system depending on the manner and style of driving;

The air supply system is not tight.

As you know, an internal combustion engine does not run on pure fuel, but rather on a mixture of fuel and air. If the engine does not have enough air, the mixture begins to get rich, which also does not bode well.

With an enriched mixture, misfires will occur, since in order for combustion to fully occur, the oxygen contained in the air is necessary.

On older cars, there is a high probability of flooding the spark plugs, since the fuel mixture will enter the cylinders, even though it does not ignite, and will fly out into the exhaust manifold without igniting.

On new cars, the system automatically turns off the cylinder injector where ignition does not occur, and the check light comes on.

Engine operating principle

According to the principle of operation, injection engines are similar to diesel engines: fuel is supplied through special nozzles. After the starter begins to crank the crankshaft, control sensors send a signal to the electronic control unit, which indicates which stroke the cylinders are in.

After reading the data, the control unit sends a signal to the injector of the cylinder, which is located on the intake stroke. The injector opens for a strictly defined time, which corresponds to the readings of the mass air flow sensor.

Mass air flow sensor value table.

After the end of the intake stroke, compression occurs. The central module receives data from the DPKF and DF sensors that the piston is at top dead center. After processing the data, the signal is sent to the ignition unit, which transmits voltage to the desired cylinder. The task of correct supply of voltage is ensured by two transistors located in the housing of the control unit.

Further, when the working mixture has ignited, the cylinder stroke has begun in the combustion chamber, the ECU takes readings from the knock sensor and adjusts the ignition angle for the next cylinder.

For more efficient use of fuel energy, an oxygen sensor is installed on the exhaust system. Using the indicators received from the sensor, the control unit adjusts the mixture composition and sets the injector opening time. If there is a lack of oxygen when the throttle valve is open, the ECU slightly opens the idle speed control.

Dirty throttle

Oddly enough, a dirty throttle valve can also cause the car to have difficulty starting when cold. As you know, the throttle valve serves to regulate the air supply to the engine.

If the throttle valve is clogged, then not clean air begins to enter the engine, but air containing various oil deposits, dust particles and other unnecessary substances, which prevent the formation of the correct mixture of the desired consistency.

Also, the throttle valve can simply jam due to excess deposits formed in it.

Diesel engines

In a gasoline engine, troubleshooting should begin with the spark plugs, and when a diesel engine has trouble starting when cold, the reasons should begin with loss of compression. A loss of compression can be assumed when the car is started after acceleration by hand, and after that it is observed from the exhaust pipe for some time. Low compression may occur if. Another reason is that the timing belt is not installed correctly. If the compression is normal, you should pay more attention to the choice of high-quality fuel (its suitability for the season), fuel supply and the next reason - glow plugs.

Ignition system malfunction.

Another common option that makes a cold engine difficult to start is a malfunction of the ignition system.

Very often, due to temperature changes, microcracks occur in the ignition coils. As we know, when a body is hot it expands. In our case, the distance between the walls of the crack becomes minimal and the microcrack does not give a breakdown, but when cold, the bodies return to their original state, the microcrack increases in size and gives a breakdown to the engine housing or body. The spark does not reach the spark plug, the mixture in the cylinder does not ignite, and the car does not start well.

This problem is inherent not only to ignition coils, but also to any other elements that participate in this process - distributor, armored wires and even spark plugs.

What can whistle under the hood after a cold start?

If you hear a whistle from under the hood of your car when you start the engine when it’s cold, there may be several reasons for this:

It must be remembered that any extraneous sound under the hood is a kind of warning about some kind of malfunction, and if you cannot independently determine the cause of the sound, then you need to contact a service station specialist, and there is no point in delaying it. After all, “breaking down” somewhere in the middle of the road in severe frost is a dubious pleasure.

It happens that you urgently need to go to work, but the car, after sitting all night, will not start. So why does a vehicle that is in good working order after the last trip suddenly refuse to start? Or does it stall as soon as you crank the engine? Let's look at the reasons why a car may have difficulty starting when cold.

First of all, it is necessary to make a reservation - your car starts perfectly if the engine has not had time to cool down, but in the case when the vehicle sits until the engine has completely cooled down, starting is difficult or completely impossible. In such a situation, even modern systems for heating and maintaining engine temperature do not always help. Let us consider in more detail the situation when a cold engine does not start well.

Causes of problematic starting of a cold engine

When determining the reasons why the car has trouble starting when cold, you will first need to make sure that the battery is not discharged and that the starter is in good working order (the engine turns smoothly and smoothly). A separate reason that requires exclusion is refueling a car with low-grade gasoline. The quality of the fuel being poured greatly influences the trouble-free starting of the vehicle. If the battery is not discharged, the starter is working properly and the fuel is of appropriate quality, you can suspect the following main problems if it is difficult to start the vehicle when it is cold:

• the fuel pump has failed;
• the fuel filter is clogged (due to low-quality fuel);
• injectors are clogged (due to fuel);
• The fuel pressure regulator has malfunctioned;
• air leak;
• the spark plugs, ignition coils, and high-voltage wires have exhausted their service life;
• clogged idle valve;
• The mass air flow sensor is faulty;
• temperature sensor malfunction;
• valve clearance violations;
• the oil is out of season.

Having considered possible malfunctions due to which the car may not start well when cold, let’s move on to studying ways to detect and eliminate them.

Low battery charge.

Let's say you arrived in the evening, parked your car, and went home. In the morning, you try to start the car, but the car won’t start. The starter does not turn, the instrument panel is blinking - the battery terminal is dead.

If the car has an old battery installed, then everything is clear, it needs to be changed and the problem will go away. But it happens that the battery is normal and the capacity holds well. In this case, you need to look for a leak in the car's wiring. In car stores, they sell a special device that allows you to determine whether there is a leak in the car in quiet mode. Perhaps some electronic device is faulty and drains the battery. Either the non-standard radio is connected incorrectly, or simply some wire has become unusable and is causing a short circuit to ground (especially true for older cars).

Let's say the leak test did not give any results, and there are no leaks, then it makes sense to check the charging from the generator. If it is insufficient, the generator will not charge the battery completely. And since it is more difficult for a starter to crank a cold engine than a hot one, it will definitely start with problems.

Problem solving

So, after you have figured out the main reasons why the car does not start after the engine has cooled down, you can begin to search for and solve problems specifically for your car. To determine the main reasons, you just need to unscrew the spark plug and look at it. Before unscrewing the spark plug, you need to turn the starter, otherwise you won’t see anything on the spark plug.

By unscrewing the spark plug, you can use it to determine whether there is enough fuel in the combustion chamber. If there are many traces of gasoline on the spark plug, this means that a lot of fuel is entering the combustion chamber. In this case, you need to look at the sensors or adjust the carburetor. If there is no gasoline at all on the spark plug, it means that it either does not get into the combustion chamber, or gets into it, but in a very small amount. In this case, the first thing you need to do is see if there is gasoline in the tank, and then check all the devices for functionality.

The second way to determine the problem is the battery. If it was noticed that when the starter rotates there is no spark at the spark plugs, then the problem is in the ignition system. The first step is to check the battery for charging. If it is, then look at the high pressure wires. They should be without the slightest damage. Next, let's look in order.

Sometimes, in order to identify a broken part, it needs to be replaced, such as the ignition coil.

You should not ignore the fact that the candles themselves may become unusable. If it is possible to install new spark plugs on your car, then it is best to do just that.

The next reason why the engine does not start is the most unpleasant, and repairing the car in this case is not very cheap. The problem is that the compression pressure in the combustion chamber has dropped. This happened because the engine was already old and began to wear out. In this case, you will need to remove the piston group and replace the rings on the pistons. This can be done independently or with the help of a car service station.

Idle speed sensor malfunction

The most common cause of cold starting problems is a faulty idle speed sensor.

The idle speed sensor is an electromagnet with a rod. It is controlled by the car's ECU. When the car is cold, the engine temperature sensor signals this to the ECU and the ECU, in turn, sends a signal to the idle speed sensor. The idle speed sensor rod extends, opening the throttle valve slightly. This increases engine speed when it is not warmed up. When the engine warms up, the ECU sends a signal to this sensor and pushes the rod back, while the speed decreases and the engine begins to operate at its normal operating temperature.

When the idle speed sensor is faulty, it does not extend the rod and does not open the throttle valve, or does not do so completely. Most often this occurs due to contamination or failure of the coil, which is located inside this sensor.

The reasons for poor engine starting include low compression in the cylinders. The car has difficulty starting when it is cold. This is true for both gasoline and diesel engines.

As a rule, many other factors signal low engine compression.

Why does a car have trouble starting when cold and with low compression? - the answer is simple. Thermal expansion of metals. When the insides of the engine are warmed up, they expand in volume, albeit slightly, but this is enough for the compression to rise a little and the engine to start. When cold, there is no expansion, and since the compression is low, we conclude that there will be poor starting of a cold engine.

In winter, many owners try to change the oil on their car. But few people know that in winter it is better to use oil that is suitable for the car, but with minimal viscosity, since too thick oil hardens in cold weather, and it is very difficult for a cold engine to drive it through the oil channels. And if there is also an old battery that does not hold capacity, then this aggravates the situation even further. This point is relevant for both diesel and gasoline engines.

Too rich or lean mixture - air flow sensor

We mentioned above that problems with starting a car can occur due to the failure of the mass air flow sensor. This element of the car is one of the most sensitive to environmental influences, so they often talk about its breakdown. If starting the engine when hot is very difficult, check the functionality of this mechanism. The following factors may also accompany this failure:

• failures when pressing the gas pedal, lack of traction at some moments;
• a decrease in power or vice versa - an inexplicable increase in the operating potential of the unit;
• complication of engine starting and periodic moments of choking;
• explosions inside the exhaust system when the gas pedal is sharply pressed;
• unstable speed due to periodic changes in mixture enrichment.

The fuel mixture of gasoline and air must have a certain consistency, which is formed by the mass air flow sensors and some other parts of the electrical and electronic system of your car. If these parts are faulty, you will have to change them and test the car, set up the operation of the new equipment.

The carburetor engine does not start when cold.

As you know, a carburetor is a mechanical fuel injection system into an engine. It is very primitive, and unlike the injector, it does not have such a large number of sensors that simplify the use of the car.

As a rule, the carburetor has a choke, which opens an additional chamber for air supply, thereby increasing the speed. If the choke is not working properly, then it is very difficult to start the car when it is cold, since the standard speed of a cold engine is not enough for its normal operation when it is not warmed up.

Troubleshooting and troubleshooting in different types of engines

A problem with spark plugs is a common cause of poor starting in a cold engine.

Different types of engines have their own trouble indicators. It happens that a gasoline engine has difficulty starting when cold, and one of the main ways to find out the cause of the problem is the spark plug. It may also be the reason why diesel engines have trouble starting in cold weather. Indications for checking spark plugs, testing the battery, checking explosive wires and the ignition coil are jumping speed, engine tripping and poor cold starting, but only when the problems go away after warming up.

If the spark plug is dry, the problem is in the fuel line, as it indicates that fuel is not being supplied to the system.

Let's examine the spark plugs. Having unscrewed the spark plug, we carefully examine it. If the spark plug is wet, this indicates an overflow of fuel. Then suspicions fall on an electrical failure. We check the high-voltage wires, then we diagnose the ignition coil and battery.

We check the performance of the spark plug itself: serviceable spark plugs have a good spark. If the spark plugs fail, it is better to replace them with new ones. High-voltage wires can be checked in a dark room - if a glow is visible in the dark, the wires have been broken and they also need to be replaced.

Diagnosis of the causes of difficult starting

When a car has difficulty starting from a cold engine to a cold one, there may be different reasons. If the indicator is a dry spark plug, this is a sign of a problem with fuel supply. This can happen due to clogged filters - fine and coarse cleaning. If the engine still has difficulty starting when cold, pay attention to the injectors.

A faulty injector may be indicated by a spark plug flooded with gasoline after an unsuccessful start.

Another characteristic feature of this malfunction is poor starting in hot weather with a warm engine, and in winter problems arise with starting a vehicle that has already cooled down. You can check whether the problem is correctly detected by reducing the pressure in the fuel system before stopping the engine for an extended period of time. The injectors may be incorrectly adjusted or leaking. Additionally, we examine the fuel system for leaks, kinks or creases. Due to damage, air can leak inside and prevent the engine from starting when cold. It happens that the starter is fine, the spark plugs and wires are normal, but the engine does not start. Then you need to look for the cause in the sensor that regulates the coolant or check the pressure in the fuel system.

Why doesn't diesel start when cold?

Diesel fuel may freeze at low temperatures. Therefore, this type of fuel has varieties for each season. In the summer, summer diesel fuel is poured, in winter, winter diesel fuel is filled, and in regions where it is very cold, “Arctic” diesel fuel is filled.

It happens that the wrong fuel was filled by mistake. The air temperature dropped below zero and it froze. Of course, the pump is unable to pump frozen diesel fuel, so the engine does not start.

Sometimes, at low-quality gas stations, water can get into the diesel fuel. After refueling with such fuel, it settles at the bottom of the tank, and can also freeze in the fuel channels or in the filter.

The engine is considered cold until it has been started for the first time.

Starting the engine when it is cold is difficult due to the fact that to start it you need an enriched mixture, the ignition of which will be difficult if there are any problems with the power plant.

If the above sensors malfunction, the engine ECU receives incorrect commands, which also affects poor starting of a cold engine.

Replace faulty sensors, first making sure that there are no problems in their power supply circuit.

Throttle assembly

Since the throttle valve takes part in the correct formation of the fuel mixture, if it malfunctions, starting the engine is difficult, since the ratio of the components of air and fuel changes relative to what is necessary for stable ignition of the mixture.

Dismantle, clean and rinse the unit, not forgetting to “register” it after installation.

Air leak

When air leaks appear in the starting system, the mixture becomes lean and starting a cold engine becomes problematic, since this requires the composition of the mixture to be as rich as possible.

Find and eliminate the air leak.

Carburetor

Poor starting of a cold engine equipped with a carburetor is caused by misadjustment of its starting system or a violation of the level in the float chamber. Make the necessary carburetor adjustments.

Injectors

On engines with an injector, unsatisfactory starting can be caused by a malfunction, when they are either clogged with dirt, the spray pattern is disrupted, or they are leaking. Also, the reason for poor starting may lie in insufficient pressure in the fuel rail.

The injectors must be dismantled and checked on a special stand.

Fuel

Often the reason may be low quality fuel or the presence of a large number of various additives in it to increase its octane number, which negatively affects the condition of the spark plugs.

For diesel engines, the quality of fuel is generally critical, especially in winter, when diesel fuel turns into a gel or mush, making its ignition impossible.

Refuel your car only at proven gas stations.

Fuel system

The condition of the fuel supply system directly affects the start of a cold engine, where the following malfunctions may be present:

Low fuel pump performance or failure;

Unadjusted fuel injectors;

Malfunction of the injection pump;

Failure of glow plugs.

To ensure a stable start of a cold engine, it is recommended to periodically undergo comprehensive diagnostics of the engine and all its systems.

As a rule, problems with the engine arise in the autumn-winter period, when it is difficult for the engine to turn over from thick oil, and the fuel cannot ignite in a timely manner in cold cylinders. However, in automotive practice there are often cases when the engine begins to “spark” not at sub-zero temperatures, but on a warmed-up engine that has just been running.

Perhaps you have also encountered a situation where a fairly hot engine does not want to start after stopping. Most drivers immediately begin to turn the starter, trying in vain to start a hot engine, which should start with a half turn.

Identifying and eliminating engine starting problems

In most cases, problems can be identified and fixed without much difficulty. So, a sign of clogged fuel filters will be difficulties starting the engine (it may stall at idle), a decrease in power, and also the car jerking during inclines.

It is worth noting that such “symptoms” can also be the result of other faults, such as wiring problems or faulty spark plugs. In this case, it is necessary to urgently replace the filters. If this is not done in time, the motor may fail.

Fuel supply can be checked by unscrewing the spark plugs. If they are filled with gasoline, or, on the contrary, are completely dry, then it is necessary to check the sensors or adjust the carburetor.

Another problem, a sign of which may be that the engine does not start when cold, is clogged injectors. In this case, the car loses dynamics when accelerating sharply, twitches and reacts poorly to pressing the gas pedal. In addition, muffled high-frequency noises may be heard coming from the cylinder block.

If the injectors are indeed coated with deposits, they need to be cleaned. You can do this yourself. There are several main ways to restore this part:

1. The first cleaning method is rather preventive. It consists of adding special additives to the fuel that help get rid of deposits on the injector. However, many motorists try to use this method as little as possible: it is believed that additives can further worsen engine performance.
2. Some experts recommend periodically turning the engine up to high speeds. After several kilometers at a speed of 100-110 km/h, engine performance should improve somewhat.
3. If the injectors are seriously dirty, you will have to clean them manually. To do this, you need to disassemble the injector. After this, the parts are washed with high-quality fuel without impurities or kerosene and blown with compressed air.
4. There are two more ways to clean injectors. They guarantee almost 100% results, but to implement them you need to use professional equipment and have certain skills. Therefore, it is better to contact a service center here. In the first case, the parts are exposed to ultrasound, which destroys all plaque. In the second, a special liquid and a device are used that is connected to the fuel receiver. After the engine has been idling for some time, the injector will be cleaned.

In order to start a diesel engine at subzero temperatures, it is necessary to approach this procedure comprehensively and perform the following actions:

• As soon as it gets significantly colder outside, it is necessary to fill the fuel tank with winter diesel fuel. If the nearest gas stations have not yet switched to it, then you can add anti-gels or kerosene (preferred) or gasoline (95 or 98) to your summer diesel fuel. The amount of antigel is indicated on the package. As for kerosene or gasoline, it is added 10% of the volume of the fuel tank, decreasing by every 10 degrees Celsius. Please note that you cannot add kerosene to diesel fuel if the car has a modern Common Rail control system.
• Using a clean fuel filter. It is advisable to change the fuel filter with a new one before the onset of winter. This is especially true for engines with a Common Rail system, since their degree of filtration is higher and is designed for smaller honeycombs in the filter.
• Use motor oil for winter. When choosing, first of all, you need to take into account low-temperature viscosity so that the oil composition is more liquid and does not thicken in cold weather. High temperature viscosity must be taken into account according to the vehicle manufacturer's recommendations. Typically, the instructions indicate that oils of different viscosities can be poured into the engine, so you need to choose a more liquid one from the list. In this case, it is advisable to choose synthetic or semi-synthetic compounds (mineral ones can be used in the summer), since they have more stable performance characteristics and retain their lubricating and protective properties for a longer time.
• Before the onset of cold weather, it is advisable to inspect the fuel system for leaks. In particular, check the clamps and pipes to see if diesel fuel is leaking somewhere. It is advisable to install a transparent tube somewhere in one place in order to see if there are any air bubbles going through it.
• To prevent diesel fuel from draining back into the fuel tank, it is advisable to install a check valve or a small pump that creates a pressure of up to 0.5 atmospheres. With its help, diesel fuel is supplied to the engine without any problems, which makes it easier to start in any conditions. Sometimes, instead of an electric pump, a manual rubber bulb is installed. Modern Common Rail systems do not have this problem, since the pump is located in the fuel tank.
• Check the operation of the glow plugs. This can be done using different methods - without removing them from the engine, using a control light, battery or multimeter. If any spark plug begins to work poorly, it is better to replace it with a new one, preferably at the beginning of winter. In general, it is recommended to change glow plugs approximately once every two seasons, even if they are still in more or less working condition. The only exception may be the warranty period or the mileage of new spark plugs.
• Failure of the glow plug relay. In some cases, the output voltage at the glow plug relay is lower than required. This leads to the fact that these spark plugs do not operate at full capacity, and, accordingly, do not heat diesel fuel well. In addition, modern diesel engines contain “smart” electronics that allow the engine to start only when the diesel fuel reaches a certain temperature. It is easy to check the operation of the relay. To do this, it is enough to use a wire with a large cross-section (4 or 6 square millimeters) to apply voltage directly from the battery to the spark plugs. If the engine starts without problems, you need to change the relay for a new one or make some kind of “homemade” with a similar wire and a button in the cockpit (but with a relay it’s still better, since it’s both automation and protection).
• Low compression. Before the cold season, it is also worth checking the compression. This is done using a compression tester in a garage or using a compression tester or motor tester at service stations. The reasons for low compression may be the following engine elements - wear of piston group parts (piston, rings, cylinder), incorrect adjustment of timing mechanism elements, burnout of valves and/or pistons.
• Check the operation of the starter. It should produce normal (high) rpm. It is advisable to carry out a comprehensive check of both the mechanical and electrical parts (stator/rotor windings, bearings, brushes).
• Charge the battery. During the cold season, you should always monitor the battery charge level, especially if it has been in use for a long time. When the battery is old, it is better to choose the best battery for your car before winter sets in. When choosing, pay attention to the fact that a diesel engine requires a battery with a higher cold cranking current than a gasoline engine. For prevention, it is advisable to remove the battery at night and recharge it from a charger in the garage or at home once a month.
• Check the operation of the generator. Even if a new battery is installed on the car, it is important that it is charged at the normal voltage provided by the generator. That is, you need to check both the operation of the generator itself and check the voltage value supplied to the battery. Usually it is about 14.2...14.5 Volts. The lower the ambient temperature, the higher the voltage should be.
• Check ignition settings. The fact is that some cars work better when the angle is still small, that is, the compression ratio is small. Others, on the contrary, start better when the fuel is supplied with a significant level of compression. Information about this can be found in the vehicle documentation or contact a car service center for help.
• Check the operation of the injectors. Do it yourself in the garage or at home. If the injectors are clogged with deposits, they can also be cleaned in a garage. As a last resort, replace the injectors with new ones. In the latter case, it is better to replace them as a set so that the old injectors do not cause problems compared to the new ones. If the Common Rail injector is leaking, you should check the multi-check valve, or it is better to immediately replace it with a new one.
• Check the fuel heater (if equipped). They operate on the basis of electric heating elements, so you need to check whether electricity from the generator is suitable for them, whether they are intact, and also check the operation of the temperature sensor, which provides information to the electronic control unit about the temperature of the diesel fuel, and accordingly, a command is generated to turn the heater on/off.

When all the parts are more or less in working order, but difficulties arise when starting the diesel engine “cold”, then follow a few simple recommendations:

• During startup, be sure to press the accelerator pedal in order to supply more fuel to the engine. This is especially important during the cold season.
• Starting a diesel engine in winter is made easier by using an external fuel heater. If the standard design of the car does not provide for the installation of the specified heater, then you can install it yourself. Currently, there are three types of such heaters on sale - for the fuel filter, for oil and coolant.
• As a last resort, when the engine does not start, but you still need to drive, you can use the “quick start” tool. The aerosol is sprayed into the intake manifold, after which the probability of starting a diesel engine significantly increases (according to their manufacturers, the probability of starting is about 90%). However, it is necessary to understand that “quick start” products cannot be used on an ongoing basis, and it is not a panacea. That is, it is still necessary to find a breakdown in the engine if it exists and eliminate it.

Conclusion

What is the reason for poor starting of a hot engine?

In fact, the issue is not pleasant, but it can be solved. The fact is that when the engine is running, a large amount of air passes through, thereby seriously cooling it. The same thing happens with gasoline, which also passes through the carburetor. As a result, it turns out that when the engine is running, the carburetor temperature is much lower than the engine temperature. This difference in temperature persists only during the operating process, but as soon as the engine is stopped, the carburetor begins to heat up intensely from the hot engine body.

Since there is no air flow, it heats up to engine temperature in a matter of minutes. At the same time, the remaining gasoline that remains in the float chamber begins to evaporate intensively due to the very high temperature, filling all the voids, including the intake manifold, and itself. The fuel gradually evaporates and almost nothing remains in the float chamber, while the evaporation often forms gas plugs in the fuel system.

The duration of this process depends on how long you intend to stand after a long trip, as well as the ambient temperature, approximately 5-30 minutes. If you decide to start the engine in this interval, a mixture over-enriched in fuel vapor will enter the combustion chambers, that is, the consistency is broken, and the spark plugs are simply flooded with fuel. This is the main reason for poor startup.

Problems with poor starting of gas cars in warm weather

Many drivers, having read all the above arguments, will say that they are not valid for their car, since it has a gas installation. It became profitable to drive on gas several years ago, so LPG has found its way under the hood of many car enthusiasts. If in hot weather your car stalls and does not start when hot, you will have to let it cool completely, then start it and go straight to the service station. It’s better not to joke with this question for a number of reasons:

• due to high temperatures, certain seals could deteriorate and gas hoses could open;
• the working fluid of your car’s fuel system may leak for other reasons;
• expansion of gas in the tank at high temperature creates a certain pressure in the system;
• It is better not to fill a full gas tank in hot weather, limiting yourself to partial refueling;
• It makes sense to consult with a specialist if such a problem begins to occur on your car.

You shouldn’t joke with gas-powered cars at all - even the latest generation of LPG carries a certain danger. If your gas car does not start when hot, it is worth hiring a specialist to solve this problem. This way, you can easily obtain the necessary operating features of the power unit, and you will not expose yourself to the danger of incorrect operation of the fuel supply system. We invite you to look at the experts’ explanations about a poor launch during the busy season:

How to make sure that the engine starts well when hot?

In such a situation, you need to act according to a certain algorithm, according to some instructions. The main task is to combine the mixture in order to allow the engine to start. To do this, when starting a hot car, press the gas pedal halfway, or even fully, depending on the situation and the carburetor itself. If you start pressing the gas frequently, you risk further aggravating the situation, because with each new press the pump will supply a new portion of gasoline to the carburetor, as a result you will simply “flood” the engine. Make several attempts, after starting, press the gas several times and continue your movement.

Starting in cold weather

Tips for winter starting the engine

If your car has trouble starting in cold weather, following simple rules can correct this situation.

• Try to keep your fuel tank full to help prevent condensation from forming and mixing water with fuel. This way the quality of the fuel will not deteriorate.

A car that runs on gas and cannot start well when cold - never start it without switching to gasoline! Is it dangerous!

• Before starting the engine, when it is frosty outside, it is advisable to turn on the high beams and turn them off after a couple of seconds. This procedure will help partially restore the battery capacity and eliminate poor starting in cold weather.
• Before starting a car with a carburetor, you need to pump up the fuel a little (be careful not to fill the spark plugs!).
• After turning the key in the ignition, if the car has an injector, do not rush to start the engine. It is worth waiting a while for the required pressure in the fuel system to rise.

“It doesn’t start well when it’s cold,” such complaints can be heard from men in cold weather when discussing cars. In this case, different symptoms and behavior may be described, but the problems due to which the car is difficult to start when cold are, as a rule, almost the same. The reasons for difficult starting may differ depending on the type of engine; since gasoline engines (injector or carburetor) have their own reasons, and diesel engines will, of course, have others. In this article we will look at the most common cases of problems such as:

Why does a hot engine stall?

An equally unpleasant situation is when a hot engine stalls while the car is moving. This phenomenon is most often observed when the thermometer column is at the highest point. The reason for this phenomenon is gas plugs in the fuel pump. They do not allow the fuel pump to function normally; as a result, there is nothing left in the float chamber, because fuel simply does not flow into it. This problem is solved by cooling the fuel pump. This is done as follows: take a damp cloth and wrap it around the fuel pump. However, this method is relevant for all-metal gasoline pumps; for models that use glass, it will not work; the glass will simply burst from the drop. If, after prolonged cooling, you still cannot start a hot engine, most likely the car has problems with the fuel pump.