No spark from the ignition coil - possible causes and solutions. Ignition system malfunctions. Lost spark? Will seek! The car won't start, no spark, what should I do?

When there is no spark after an unsuccessful attempt to start the engine, or the spark on the spark plugs suddenly disappears and, of course, the engine does not start, then some novice drivers do not know where to start to get rid of this malfunction. This article will describe the reasons why a spark may be absent or appear every once in a while, and will also discuss methods for simple diagnostics (troubleshooting) of the ignition system.

I have already written about repairing the ignition system and you can read about it in detail here. It describes in detail the testing of all components of the ignition system, both the modern contactless electronic and the more ancient contact ignition system.

But this article will describe when there is no spark, the reasons and specific actions to ensure that a spark appears on the spark plugs.

No spark causes and solutions.

• 1. Let's start with the simplest and gradually move on to more complex reasons. The first and most commonplace reason is discharged. Of course, this can be determined without a voltmeter, since a discharged battery will not crank the crankshaft with an electric starter of a car or motorcycle. But many drivers, after an unsuccessful attempt to start with an electric starter, try to start the car with a pusher, hoping that the energy of the discharged battery is not enough for the starter, but is quite enough for the ignition system. In most cases this is not the case.

And if the energy of a discharged battery for a contactless electronic battery in most cases is enough to cause a spark and a successful attempt to start the engine from the pusher, then for an older contact system, the energy of a discharged battery will not be enough to cause a spark (especially if the contacts are burnt and this happens often). Therefore, in order not to guess and not waste human energy on pushing the car, we simply bring the battery back to normal using. Beginners can read how to properly charge the battery.

• 2. Another simple and banal reason why there will be no spark on the spark plug is that it is simple or simply necessary to clean the spark plug (how to check and properly clean the spark plug). Of course, the spark plugs don’t all fail at once, and if one of the spark plugs fails, the four-cylinder engine will simply start to stall. Therefore, this reason is only suitable for single-cylinder motorcycle engines, but still it was worth mentioning, let’s move on.

But before checking and cleaning a non-working spark plug, try swapping the high-voltage wires and if a spark appears on a previously non-working spark plug, then the reason is not in the spark plug, but in the spark plug wire, which should be replaced.

• 3. The third reason for the loss of spark, which often happens on used cars and motorcycles, is there is no voltage at the ignition coil terminal after turning the ignition key. Using a tester set to voltmeter mode (measuring direct current), you should measure at the coil terminals whether a voltage of 12 - 13 volts is supplied to terminal B+ of the coil (see figure) when the ignition switch is turned on. If it doesn’t, then you should check the integrity of the wire going from the lock to the coil (or from mounting block to the coil - the GP wire in Figure 1), and also check whether the terminals are oxidized.
• 4. If voltage comes to terminal B+ of the coil after turning on the ignition switch, but there is still no spark, then you should check the integrity of the wire and the cleanliness of the terminals of the wire coming to the distributor from the coil (the black wire marked with the letter C in Figure 1) and in general check all the wires and terminals of the low-voltage circuit of the ignition system (check the wires marked with the letters G and K, as well as GC and K. It also wouldn’t hurt to check the operation of the ignition switch itself 8 and the ignition switch relay 7, which rarely fail but still fail. And of course, we check the integrity of the fuses responsible for these circuits (in general, I advise beginners to check all the fuses at the very beginning).
• 5. Contactless electronic system ignition switch, you should use a voltmeter to check the presence of a voltage of 12 volts (after turning on the ignition switch) at terminal B+ of the ignition coil, as well as at terminal 4 of the switch and check the integrity of the wire marked with the letters GP in Figure 2. We also check the integrity of the wire and the cleanliness of terminals K of the coil and terminals 1 on the switch and the integrity of the control wire of the gearbox connecting them.
  We also check the integrity and reliability of the connection (cleanliness of the terminals) with the car body of the black wire marked with the letter H in Figure 2, which connects terminal 2 of the switch to the car body. What can happen on the car due to poor contact of a lot of other wires, I advise you to read this useful article.
• 6. Next, we check the integrity of the wires and the reliability of the connection between terminals 3, 5, and 6 of the switch and the Hall sensor (wires marked with the letters Z, P and BC in Figure 2). If the terminals are securely connected and not oxidized, and the wires are intact, then we check the functionality of the hall sensor itself (how to do this). Well, you can find out how to check the functionality of the switch and ignition coil by clicking on the very first link at the beginning of this article, in the article about repairing the ignition system).
• 7. Having checked the low-voltage circuit of the ignition system, as described above, if everything is in order and a spark has not appeared, then we check the high-voltage part of the system. If there is no spark on any spark plug, then first of all we check the central high-voltage wire G (see Fig. 2), connecting ignition coil 5 and distributor 1. The tips of this wire must be clean and must be tightly inserted into the mounting sockets of the distributor cover and the ignition coil . We check the wire itself for integrity using a tester set to ohmmeter mode.
• 8. If there is no spark on only one spark plug out of four, then we check the high-voltage wire of the non-working spark plug (you can swap the wires, as described above, or check the wire of the non-working spark plug using a tester). Also, having removed the distributor cover, we check it for integrity (there should not be even the slightest cracks) and the cleanliness of all contacts inside and outside the cover, and the integrity of the carbon (graphite cylinder) in the center of the cover.

Also pay attention to whether the contacts on the system with contact ignition are burnt (we clean them), also check the required gap between the contacts using a feeler gauge (more about this in the article about repairing the ignition system - link to the article at the very beginning of the text).

• 9. Another common reason for the loss of a spark is the burnout of the resistor in the slider (and the sliders are different, as can be seen from the figure just above), indicated in the figure by yellow arrows. To make sure that there is no spark precisely for this reason, you should check the integrity of this resistor with a tester (turned on in buzzer or ohmmeter mode - the resistance of a working resistor should be approximately 5 - 6 kOhm). For those who don’t have a tester on the go, and also need to somehow get home, you should simply wrap the resistor with a piece of foil and insert it into place. If a spark appears, then of course the problem is in the resistor.
• 10. It happens that the spark disappears (or appears every other time) due to the failure of the capacitor (installed on the breaker of the oldest cars or domestic motorcycles). This can be easily treated by replacing the capacitor. I wrote how to check the capacitor in the same article about repairing the ignition system (the very first link at the beginning of this article).
• 11. On the latest injection machines, the engine will not start due to the failure of the crankshaft sensor, but we read how to replace or check it, as well as. Also, a loss of spark occurs when the ignition module (ECU) fails, which fails quite rarely. In this case, you will have to look for a working unit and install it to replace the faulty one (buy a new one or look for it at disassembly).

That seems to be all the nuances, when there is no spark, the cause and methods of eliminating them on your own, good luck to everyone.

Therefore, every VAZ 2109 owner should know the solution to this issue.
So, the main reasons that there is no spark in the VAZ 2109 are as follows:
1) The VAZ 2109 switch has failed
2) The Hall sensor of the VAZ 2109 has failed
3) The timing belt of the VAZ 2109 is torn
4) The ignition coil of the VAZ 2109 has failed
5) Contact group of the ignition switch VAZ 2109
6) Contacts of the ignition distributor cover of VAZ 2109
7) Malfunction in the wiring (any of the wires of the electrical circuit ignition switch-switch-ignition coil-Hall sensor is torn off or bent).
Above are the most basic faults due to which there is no spark on the VAZ 2109. Let's look at each of them in order. Let's immediately make a reservation that the VAZ 2109 must have a charged battery that rotates the engine crankshaft. If your starter does not turn over crankshaft engine of the VAZ 2109, then first get it to spin, and then look for a spark.
1) To check that the switch on the VAZ 2109 is working, it must be replaced with a known good one.

Experienced owners of the VAZ 2109 know that the VAZ 2109 switch is not the most reliable part, so it is always necessary to have a spare switch in the glove compartment. We remove the switch under suspicion and install a known good one.
We try to start it - if it starts, then the problem is in the switch. If it doesn’t start, we put the old switch back and look further.
2) To check the Hall sensor, it is also better to replace it with a known good one, although there is a test method directly on the VAZ 2109.

We replaced the Hall sensor and tried to start it again. If a spark appears, then the problem was in the Hall sensor. If a spark does not appear on the VAZ 2109, move on.
3) To make sure that your timing belt is not broken, remove the cover from the ignition distributor and turn the crankshaft with the starter.

The ignition distributor slider should turn. If it doesn't turn, change the timing belt.
4) The ignition coil fails quite rarely, so it is better to check it as indicated. If the check indicates a malfunction of the ignition coil, change it and look: a spark appears, which means the problem is in the coil, if it does not appear, move on.
5) The contact group of the ignition switch can also be the reason that there is no spark on the VAZ 2109. I had the following thing: after two days in the cold, for some reason the spark on the VAZ 2109 lost. The starter turns briskly, but there is no spark. I noticed that when you turn on the ignition, there is power to the ignition system at pin B of the ignition coil. When turning the starter, the power from contact B of the ignition coil disappears.
The thing is incomprehensible and difficult to diagnose; you need to measure the voltage between ground and contact B of the ignition coil with a multimeter or a light bulb. To crank the starter, you need to turn the ignition key and somewhere in the contact group of the ignition switch there is no contact, so when the starter rotates, power is removed from the ignition system. It can be treated by replacing the ignition switch contact group, or as follows:
Using a locking button, we connect +12V from the battery to contact B of the ignition coil.

We pressed the button, +12V went to the coil and the ignition system will be powered even when the starter rotates.

A spark will appear, start it, press the button again to break the direct circuit from the battery to the coil. If the button is left pressed, the VAZ 2109 will not stall when the ignition is turned off. This method is quite acceptable, as in my case: the VAZ 2109 car is parked in -20 degrees cold, and it needs to be started. Change the ignition contact group in in this case not the fastest or most convenient solution. You won’t do anything bad with a button from the battery to the coil. When you have time, you can safely make repairs somewhere in the garage, and put the jumper with the button in the trunk and save it just in case.
6) In general, when there are no sparks on the VAZ 2109, this must be checked first. First of all, if there is no spark on the spark plug of the VAZ 2109, then you need to check whether there is a spark from the ignition coil.

We remove the central wire from the ignition coil, bring it a centimeter closer to ground and turn the starter. If there is a spark, then remove the cover from the ignition distributor. We check the integrity of the slider resistor, clean the contact of the ignition distributor cap.

7) The last problem due to which there is no spark on the VAZ 2109 is a malfunction in the wiring of the ignition system. As a rule, very often they are visible to the naked eye: wires are torn off or melted, connectors of the switch and Hall sensor are poorly connected.
But if visually everything is in order, then the malfunction can be determined only after testing all the wires of the ignition system with a multimeter. Naturally, not everyone knows how to use a multimeter, so if the reasons described above did not help you find a spark on the VAZ 2109, then we ask for help from an auto electrician.

Like any other malfunction, a malfunction of the ignition system is unpleasant and untimely, but unlike others, it can cause a lot of trouble when trying to diagnose, that is, find out the cause of the breakdown and inoperability of this system. Today we’ll talk about the situation when there is no spark and the engine is not working properly. which one doesn't want to start. In this article, I will talk about the most likely reasons why the spark disappears and how to find the reason at home.

The main signs of a faulty ignition system are unstable engine operation (,), poor starting or a complete lack of spark on the spark plugs. If the spark is lost, it is necessary to establish exactly the reason why this happened, for this it is necessary to decide on the “circle of suspects”.

The main reasons why there may be no spark

1. First of all, make sure that there is no dust, dirt, oil stains, etc. on the ignition system elements. If any of the above is present, take a rag and wipe everything thoroughly, or blow it out with compressed air, and then try to check the spark again and start the engine.
2. The spark plugs are faulty (flooded, insulator burst, breakdown, etc.). Check the spark plugs individually and make sure there really is no spark. If there is no spark on all the spark plugs, then the reason is most likely not in the spark plugs, but in the coil or, for example, the starter. We read: and. If there is a spark, but it is weak or yellow, check the coil or BB wires.
3. The problem is in high voltage wires (HV wires). This could be a break, a ground fault, or poor contact. Carry out a detailed inspection of the explosive wires, make sure that there are no cracks or fractures on their surface. Move the wires and try to start the engine, if the engine starts or at least tries, most likely the reason lies in the wires. Details about .
4. Malfunction of the ignition module or ignition coil. How to check the ignition coil .
5. The crankshaft sensor has failed, read how to check
6. The problem is in the switch, distributor, incorrect clearance, burnt contacts.
7. There is no contact on the ground wire or it is very bad.
8. ECU malfunctions.

Methods for checking spark on spark plugs:

1. Check for weight;
2. Using a multimeter;
3. Using a tester based on a piezoelectric element.

Lost spark (injector)

As for injectors, everything is a little more complicated. Checking the spark in spark plugs using the “ground” method in injection engines is not always possible, in some cases it is extremely dangerous, and there is a high probability of damaging the ECU. Therefore, it is better to check candles using other methods.

If the spark disappears on all cylinders at once, the reasons may be the following:

• The controller has failed;
• The entire ignition module is faulty;
• The central wire is broken.

The check must be performed one by one, starting with the fuses, then check the condition of the contacts of the explosive wires and ground.

Malfunctions of ignition systems are always unpleasant, because each of them negatively affects the operation of the car engine. The latter either stops, stalls or does not start at all. This development of events is known to many owners of old cars equipped with a distributor.

What is ASZ

ATTENTION! A completely simple way to reduce fuel consumption has been found! Don't believe me? An auto mechanic with 15 years of experience also didn’t believe it until he tried it. And now he saves 35,000 rubles a year on gasoline!

There may be several reasons for the lack of sparking. Most often, the culprit is the distributor with its elements. But no less well-known reasons are: a bad battery, the armored wires themselves, the ignition coil or its winding.

As you know, the car ignition system or ASZ is designed to effectively ignite fuel. It is clear that without a spark there can be no talk of any ignition. It is not for nothing that the ASZ of a gasoline engine is also commonly called a spark ignition system.

Depending on the type of process control, there are several gas stations. On domestic classics, for example, a contact ASZ is used, and on foreign cars - transistor or electronic.

The distributor in the contact ASZ plays the role of a current and energy distributor across the cylinders. At the same time, it acts as a current energy storage device.

If in a contact ASZ accumulation and distribution are carried out in a single mechanism (distributor), then in a BASS (transistor system) a switch is responsible for accumulation, clearly interacting with the Hall sensor. As for the distribution of energy, it is still controlled by the distributor.

It is noteworthy, but in most cases the spark disappears at the most inopportune moment. For example, if you urgently need to go somewhere in your car.

The old-fashioned way of “revitalizing” a contact

That's usually how it goes. Yesterday the car was fine, it started the first time. In the morning - like “dead”. Any motorist who understands cars will remove the spark plugs, inspect and check them first. No spark.

Further checking is carried out on the coil. It is necessary to inspect the main armored wire to see if current flows through it. No spark again?

Here's what to do:

• Check if current is flowing to the bobbin (coil).
• Check if voltage is going to the switch.

If there is voltage, but the spark does not go through the armored wire, the first doubt falls immediately on the woman. She is removed, checked thoroughly, and called. Is she working? It would seem like an opportunity? But this happens often. Don't panic.

And here the distributor itself, the distributor, comes to the fore. It is dismantled, the hall sensor is removed, cleaned of oil (sometimes it gets inside).

As a rule, these actions are enough for a spark to reappear on cars with a non-contact ignition system (non-contact ignition system), where the distributor becomes the “culprit” for the voltage loss. And the reason that the spark has disappeared is either oil getting into the sensor or a loose contact.

This often happens: the wires/communications connecting the switch and distributor provide unreliable, weakened contact. The old “old-fashioned” method of touching everything with your hands is 100 percent effective here. In this way, you can “reanimate”, “revive” the contact.

This method will help you save on the purchase of a coil, hall sensor or switch. It is not uncommon for amateurs in car service centers, who have little understanding of the matter, to send the car owner to the store for parts that are actually in full working order.

Searching for the spark

A spark in the distributor should appear between the contacts (between positive and ground). This can be clearly seen if you remove the distributor cap.

You can check whether there is a spark or not on an open distributor (with the cover removed) as follows: turn on the ignition (turn the key half a turn), go to the distributor, turn the slider several times (rotate it). A spark must appear between the contacts.

You can check whether current is flowing through the coil wire like this. Take a portable diagnostic tool (two wires with a light bulb). One wire is connected to ground, and the second with a probe is placed on the contact of the distributor. If the light bulb lights up, then there is current. It goes through the reel armored wire 100 percent.

You can check the spark without a device.

• We remove the main armored wire of the coil.
• Remove the distributor cap.
• Turn on the ignition.
• We turn the slider as in the case described above, but look at the armored wire.
• We see a spark.

In a word, the process of finding a spark can be simplified if you carry out several sequential checks.

1. Make sure the battery is in good order. You can check it different ways. It will be very effective to check the battery for the horn. In other words, beep - if the sound is strong, it means the battery is in order and produces normal current.
2. Check the armored wires. They should be inspected carefully for insulation failure. It is recommended to check the spark plug wire tips. They must be brought 5 mm closer to the ground (any part of the car body), and then turn on the ignition. The spark should be bright and blue-white (provided that the spark plug is in order). If there is no spark, the search continues.
3. The reel or coil is checked like this. The main armored wire is pulled out from the distributor cover (the one that goes to the coil). Place it so that the tip does not touch anything, but is clearly visible. The starter turns on, if a spark appears at the end of the wire, the search for a spark must be continued. If there is no spark, the valve is faulty.
4. Checking the distributor should begin with inspecting the cover. It is recommended to wash it with gasoline, just in case, and then inspect it for cracks. Be sure to inspect the central graphite rod of the lid. Check its operation. And it is important to definitely check the rotor. If everything is in order with the distributor, the search automatically switches to the LV (low voltage) circuit.
5. To check it, as a rule, a portable device with a 12-volt lamp is used. The power of the control indicator should not exceed 3 W. One end of the carrier is connected to the LV terminal of the distributor, the other - to the ground of the car. Now you need to turn on the ignition and check if the light is on. Normal mode – the indicator goes out when the contacts are closed and lights up when they are closed. If the light does not go out at all, then either the contacts of the breaker are heavily oxidized, or there is a broken wire.

The worst thing at the beginning of the day for any driver is when we get into the car and try to start the engine and realize that the car won’t start. We have seen more than once in movies how, at the most inopportune moment, a movie character’s car will not start. Surely some car enthusiasts are familiar with the reasons why a car engine may not start, but, nevertheless, for most car owners this trouble can be very frightening. Let's find out why the car may not start.

Sometimes some drivers modern cars They believe that there cannot be any problems with starting the engine. But in reality this is not so. There are many reasons why your car may refuse to start, even if dashboard no engine error warning (). Unfortunately, many car owners believe that if the engine does not start, then this is a serious malfunction that requires competent, qualified assistance. This is partly true, of course. But before you go to the technical center,...

For an engine to start successfully, four elements are required: spark, oxygen (air), fuel and compression.. Let's take a step-by-step look at each step that you need to take to determine the cause of the malfunction, as well as fix the breakdown yourself.

Remember, everything described in this article is just the basics. Most of the tips apply to most cars. But, nevertheless, it is necessary to understand that for some Vehicle Other methods of diagnosing and eliminating the cause of the engine not starting may be necessary.

Step 1: Check for spark

Check the spark plugs on the engine internal combustion quite simple. Unscrew one spark plug from the engine and connect it back to the high voltage wire. Next, you need to place the spark plug on the metal part of the engine. Have someone turn the ignition key. . Remember that before starting the starter, make sure that there are no flammable liquids (including gasoline) near the spark plug. When starting the ignition, do not hold the wires or the spark plug with your hands. To know if there is a spark in the spark plug, all you have to do is look. You should see a spark on the spark plug electrode. If it is not there, then your car has problems with spark plugs or high-voltage wires .

E If your car shows you a good spark at the spark plug (as in the photo), then you can be sure that the spark plug and high-voltage wires are in good condition.

Note: In the picture you can see a spark that comes from the spark plug towards the “ground”, which in this case is located on the metal pipe clamp. So it is not necessary to place a spark plug on the spark plug to check the spark. Also, if you can't get to the spark plugs, you can use an inductive spark plug tester to check for spark, which lights up when it detects a magnetic field that comes from electricity running through high-voltage wires.

Why is there no spark at the spark plugs?

There are many reasons why a spark did not appear during diagnosis. For example, the absence of a spark may indicate a malfunction of the ignition module, a broken ignition coil, a malfunction of the crankshaft position (CKP) sensor, a camshaft position sensor, and for many other reasons.

The sensors are easy to check yourself if you can easily get to them . To begin with, we would recommend connecting a special scanner to the diagnostic connector, which can read error codes that appear when various sensors installed in the car malfunction. If you do not have such equipment, then you can contact a car service for electronic diagnostics. , then you can check the performance of the sensors using a voltmeter by measuring the resistance. When taking measurements, the resistance should be as specified in the sensor manufacturer’s description (can be easily found on the Internet).

Don't forget to also check the fuse relays to make sure that the reason for the lack of spark is not in that part of the car.

Of course, the best thing is that the cause turns out to be a faulty spark plug or high-voltage wire. This is the most easily fixable fault that can exist. The problem with faulty sensors that prevent the engine from starting is also easy to fix. If the problem (lack of spark on the spark plugs) is not due to the reasons described above, then check the ignition coils for functionality.

In order to check the ignition coil, it is necessary to disconnect it from the high-voltage wire . Next, you need to ask someone to turn the ignition key in the cabin. Your task is to determine whether the current is flowing to the ignition coil. If electricity is flowing normally to the coil through the wires, then most likely your ignition coil is failing or has failed. If there is no current flowing to the coil, then the reason is different .

Step 2: Check the air filter

If you are faced with the fact that after turning the ignition key (or pressing the stop-start button), the car engine does not start, then first check the air filter. The point is that for successful launch The engine needs a sufficient amount of clean air. If the air filter is clogged with dirt or dry leaves, the flow of oxygen may be obstructed, resulting in...

Along with the filter, you should also check the air intakes and ducts, which may also be clogged with debris.

In the photo you can see a filter that was recently replaced. Therefore it does not need to be replaced. Remember that insufficient or no oxygen is a common cause of engine failure.

If the air filter is clean and not worn and all air intakes and air ducts are in acceptable condition, then check for leaks from the vacuum pipes of the engine intake system . For example, due to their damage, excess oxygen may enter the intake system. For this reason, the engine may not start.

Remember that it is not always possible to visually detect damage to the intake pipe system. You can quickly check the tightness of the pipes only by ear. .

Step 3: Check the fuel system

If you have made sure that there is a spark in the ignition system and air flows freely into the engine, now it’s time to check the serviceability fuel system. Any car owner knows that without fuel the engine will not work.

Naturally, if your car has a problem with the fuel system, then you will not start the car . Some car enthusiasts sometimes check with a syringe that is filled with fuel. Next, you need to inject gasoline into throttle valve. After this, you need to turn the key in the ignition to start the starter. We do not recommend performing a test like this if you are inexperienced and unfamiliar with car repairs. Also, never spray fuel near the sensor. mass flow air. Is it dangerous.

If you nevertheless decide to carry out such diagnostics, as a result of which the car starts, then probably the cause of the malfunction that prevented the engine from starting is in the car’s fuel system .

What could be the reason for the lack of fuel supply to the engine?

If your car's engine does not receive enough fuel, the culprit may be the fuel pressure regulator (fuel pump element). Also, the reason for the lack of fuel supply to the engine may be a fuel leak, dirty fuel filter and clogged injectors.

But most often the cause of the malfunction is the fuel pump (fuel pump) . The serviceability of the fuel pump can be checked independently quite easily.

First, you first need to determine its location in the car. Depending on the make and model of the car, access to the fuel pump is located in different places. Most often, access to the pump is under back seat. In some cases, it may be necessary to remove the fuel pump to gain access.

For example, on a BMW 325Ci, access to the fuel pump is under the rear seat . Once you have access to the fuel pump, perform the following diagnostics. Have someone on your command turn the key in the ignition for 3 seconds. At this point, you should lean your ear closer to the location of the fuel pump. When the starter operates, you should hear a sound (such as in the video). If, when starting the ignition, no sounds come from the location of the fuel pump, then either the fuel pump is not receiving power from the car’s electrical network, or it has failed.

The pump in the video showed signs of working, but the car, however, would not start. In order to determine the cause of the malfunction, first we must check the flow of current to the fuel pump. How to do it?

Everything is very simple. Connect any volt-ohmmeter or multimeter to the fuel pump connector. Have someone turn the key in the ignition and hold it to the ON position for 3 seconds. During our test measurements, the multimeter showed that our fuel pump receives electricity from. This is what made us think that the fuel pump was the culprit.

Next, you need to measure the resistance of the fuel pump by connecting a multimeter to the pump power terminals. This must be done if you do not hear the pump running when starting the engine. After measuring the resistance, compare the values ​​obtained with data that you can easily find on the Internet.

If your values ​​differ significantly from the published data on the Internet, then it is likely that your fuel pump has failed.

In the photo you see our measurements, which showed that the resistance in the fuel pump is noticeably different from normal values.

If, as a result of the diagnostics, it turns out that the fuel pump is in good condition and is properly supplied through the fuel system and there is no leakage from the gas line, then it’s time to check the fuel pressure in the fuel rail (not all cars have a similar system).

In order to carry out diagnostics, you need to buy or rent a pressure gauge to measure the pressure in the fuel system. You will also need a fuel hose, a cap for unscrewing the nipples and two clamps. The hose must be connected using a clamp to the pressure gauge. On the fuel rail, unscrew the plastic cap and screw in the cap to unscrew the nipples. Connect the hose to the cap, clamping it with a clamp.

Measure your blood pressure. If it is zero, then the system has failed. If you do not have a pressure gauge, then you can check the performance of the system using a needle and napkin. Place a napkin and press the needle on the valve, which, when in working condition, should release excess pressure.

If your car is equipped with a carburetor, then you can also check the functionality of the fuel system. To do this, disconnect the fuel hose from the carburetor and place it in a glass jar or plastic bottle. Next, start the engine. If your carburetor is in good condition, fuel will begin to flow into the can or bottle. If fuel does not get from the fuel hose into the can, then the reason is a malfunction of the carburetor, which can have many problems (stuck float, rust in the carburetor channels, carbohydrate deposits, etc.) .

Step 4: Check Engine Compression

If, after checking the spark for oxygen supply and fuel supply, you have not established the reason for the engine starting, it’s time to check the compression ratio in the power unit. The fact is that the above three components are not enough to ignite the fuel. The fourth component for successful engine starting is a sufficient degree of compression inside power unit.

An easy way to check compression is to purchase or rent a compression tester. This device is installed using a hose in the place where the spark plug is installed (see photo). During the test, it is advisable to disconnect the fuel pump relay and ignition coil. Your task is to measure the compression in the combustion chamber of the engine. After installing the hose with the compression gauge into the spark plug hole, you need to turn the ignition key. As a rule, the compression should be at least 9.5 atmospheres for gasoline engines. The compression is much higher due to the characteristics of fuel ignition (at least 28 atmospheres).

To more accurately diagnose the engine condition, it is necessary to check the compression in each engine cylinder. To do this, unscrew each spark plug in turn and measure the compression ratio in each cylinder with a compression gauge. Remember that uniform compression ratios in each engine cylinder are important. The difference in compression ratio between cylinders should not be more than 0.5-0.9 atmospheres. If the pressure difference between two cylinders exceeds 0.9 atmospheres, then this should serve as a serious reason for you to conduct a more detailed engine diagnosis.

Here you can see how we measured the compression in the BMW 325Ci. As a result of the compression ratio test, we found that the compression in each cylinder is 12.5 atmospheres. In the end we crossed it off the list. possible malfunctions, which led to failure to start the engine, compression problems.

Note. On some cars, it is difficult to access the spark plugs, which can ultimately become an obstacle to measuring compression.

You don't have the opportunity to buy or rent a compression gauge? No problem. There is an old-fashioned way with which you can find out whether the compression ratio in the engine is within the established norm. To do this, unscrew the spark plug and place your finger in the hole. Have someone turn the key in the ignition. If you cannot keep your finger in place during this test, then the engine has a normal compression ratio. If you have no problem holding your finger on threaded connection spark plug socket, then most likely your engine has problems with the piston system .

The reason for low compression in the engine

A low compression ratio is usually the result of some kind of mechanical failure. For example, it could be that the belt has either torn or slipped by one “tooth”. Also, a low compression ratio may be due to wear on the engine piston system.

As a rule, over time during vehicle operation, the piston rings or cylinder block walls wear out in the engine, which leads to a decrease in compression in the combustion chamber. If, when trying to start the engine in exhaust pipe If fuel is present, then the likely cause of failure of the power unit is damage to the piston system (crack, etc.).

In order to check piston rings you can do a compression test with engine oil. To do this, before installing the compression gauge on the spark plug hole, add a little to the cylinder. After this, installing a compression gauge, measure the compression ratio in the cylinder. If it turns out that the compression ratio with the addition motor oil becomes larger in the cylinder than when measured “dry”, then most likely a large gap has appeared between the piston rings and the engine cylinder wall due to wear, which leads to a decrease in compression. The fact is that when you add oil, you close this gap with an oil layer for a short time, which ultimately leads to increased compression in the cylinder .

What to do if the starter does not turn when starting the engine?

In 99 percent of cases in which the starter does not turn when the engine starts, there are problems with the battery. But wait, you claim that you already changed it only a few months ago? Regardless, check your battery anyway, no matter when you bought it. This can be done using a multimeter by measuring the voltage. Also check the high-voltage wires and wires, which should not be oxidized or damaged.

If with battery and the high-voltage wires are fine, then you need to check the starter relay in the power distribution block. Even if you think that this is not the reason for the starter failure, you should still check the starter relay to prevent its failure.

Finally check the starter itself (pictured above). First of all, tap on its body with something heavy. For example, with a mount. Next, try starting the engine again. If after this you hear a slight noise from the starter, but the car still does not start, then it is likely that the starter has failed. Remove the starter from the car and take it to a workshop that diagnoses and repairs starters. You can also immediately purchase a new starter .

What is the cause of the malfunction in our car?

As you already understand, we are faced with the problem of startup failure BMW engine 325i. Together with you in this article, we carried out diagnostics step by step for the possible cause of the breakdown. As a result, when checking the fuel pump (see above), we did not hear the sound of the fuel pump operating. We also took measurements with a multimeter and found that the resistance of the fuel pump does not correspond to the manufacturer's specifications, which we found on the Internet. Additionally, we found no fuel pressure at the fuel rail under the hood.

In our car we determined that there is a spark, that the condition air filter is at an acceptable level, and the engine compression ratio is normal. As a result, we came to the conclusion that the cause of the malfunction was the fuel pump. We bought a new fuel pump and installed it in the gas tank. And in the end ours started.

So if your car refuses to start, remember that it requires four ingredients: spark plugs, air, fuel and compression. By checking each of the components sequentially, you will definitely find the cause of the malfunction.