Early in the morning, freshly shaved and full of great plans, you jump into the car, "key to start" and... What the hell?! One more time. One more... Nervous manipulations with the key in the ignition and pedals do not bring success. The day is ruined from the very beginning. Plans and mood - "down the drain".
Calm down. No need to rush under the hood in an English suit and, smearing the dirt with your tie, try to make a diagnosis. Most likely, you won't cure him in five minutes. Take another car and leave the treatment of your sick friend until the evening. And it's better to entrust it to "doctors" with a good reputation, especially if you are not a specialist. It will be cheaper. Well, if your friend is well known to you and you consider yourself a healer – well, try it yourself if you are not too lazy to get dirty or there is no other way out.
You need to approach the diagnosis calmly: mentally study the symptoms. First, does the starter "turn"? If so, how vigorously? You already know the answer - remember what happened during the first attempts to start the car. If you don't remember, try again.
If the starter does not turn at all and does not even click the traction relay when the ignition is turned on, then it is either faulty (you can close the hood and follow the advice given above: "Take another car..."), or the electrical power circuit of the starter is faulty (the battery is disconnected or dead). Only on rare models can the starter power circuit be protected by a fuse. It is not difficult to find, especially if you know in advance where it is. If the battery is at fault, then, in addition to the starter, as a rule, all electrical equipment does not work. The simplest and easiest case is when one of the terminals has come off, become dirty or oxidized, but the battery is in order. Tighten the terminal fastenings on it and on the starter (if any). If it turns out that the battery is completely dead (forgot to turn off the parking lights at night), you can still leave, but with outside help. Here, as they say, there are options. You can try to start it by pushing, on a hill or by towing. However, don't be fooled: a car with an automatic transmission or electronic fuel injection (if there is an electric fuel pump) you won't be able to start it using these methods. You'll have to "jump start" it from your neighbor. However, in some cars this can lead to damage to the "computer" - the central unit of the electronic engine control system (read the car manual).
If the starter turns, but sluggishly (this happens in the summer, winter is a subject of a separate conversation), most likely, the battery is almost completely discharged. This will be visible by the weak light of the headlights or the sound signal. In this case, the above-mentioned options for outside help come into play.
If the starter turns vigorously, but the engine does not respond to attempts to start it, boldly exclude from further considerations everything related to the battery. Check the ignition or fuel supply system, you will not go wrong. When determining the diagnosis and treatment of the "disease" of each of the systems, a systematic approach is necessary. It is best to start with the ignition - in this system, malfunctions occur more often, especially in damp weather.
So, you need to "look for a spark". Your car is equipped with an electronic contactless ignition system, which can be integrated into the electronic engine management system. In any case, the ignition system consists of three parts. Part one is low-voltage (a special sensor plus a box with electronic components that generates a spark). Part two is the step-up transformer, commonly known as the ignition coil. Part three is the high-voltage (mechanical or electronic ignition distributor and high-voltage wires of the ignition system, through which high-voltage current is supplied to the spark plugs). And, naturally, the candles themselves. The inspection of all this equipment must be carried out step by step and it is better to start "from the end".
Stage one
High-voltage part of the system. Check if there is a spark on the central wire - this is the one that connects the ignition coil to the distributor. The tip of the wire must be removed from the distributor cap and brought closer to any part that has good contact with the "ground" (body) of the car (it doesn't matter whether it's painted or not), and secure it so that there is a gap of 5-7 mm between the tip and the selected part. The wire must be secured especially securely: if it falls on the "ground", the electronics will immediately "call it a day". For the same reason, you cannot "scratch" the wire along the body. We also do not recommend holding it with your hand, not even your own - it will give you a serious electric shock.
Stage two
Turn the engine over with the starter. Watch what happens at the tip of the wire. There are two possible options. The more favorable one is that there is a spark. Powerful, accompanied by a loud click. This significantly narrows the field of further searches.
The first thing you need to do is remove the distributor cap. It may be damp and dirty underneath. A spark readily jumps anywhere along such a "conductor" except where it should.
Wipe, clean and dry. At the same time, it would not hurt to clean the distributor contacts, for example, with fine sandpaper. Inspect the so-called "runner". If you find a dark trace of electrical breakdown on it or on the distributor cap, the part will have to be replaced. Check the wires going from the distributor to the spark plugs most carefully. The wires and their tips should be dry and clean. If, in your opinion, everything is in order with them, you can put the cap back in place, restore the connections and try to start the engine. If the malfunction was hidden under the cap, the engine will start or, in the worst case, at least start sneezing. This is also a favorable symptom - you are on the right track. True, you will have to unscrew, clean and dry the spark plugs: in attempts to start the engine, you flooded them with gasoline. If the engine does not even sneeze, the spark plugs will still have to be unscrewed, cleaned and checked. It is easier if you have a spare set.
If you have already reached the stage of turning out candles, you can do it quite effectively (and spectacular) check the ignition system as a whole. Having connected the high-voltage wires of the ignition system to the unscrewed spark plugs, gather the spark plugs into a bundle, like carrots, and wrap it around the threaded part of the spark plugs with a soft bare wire. Make sure that the wire contacts each spark plug, but does not touch their central electrodes. Connect the free end of the wire to the "ground". Having placed the bunch of spark plugs in a place convenient for observation from the passenger compartment, turn the engine with the starter. Between the electrodes of the spark plugs in turn (in accordance with the order of cylinder firing) there should be cheerful sparks. If so, the entire ignition system is in good working order. The engine sound will be very unusual, but don't be alarmed, because it is spinning with the spark plugs removed. Don't spin it for too long. It is worse if another option occurs at the second stage of checking: there is no spark between the central wire and the "ground". This means that the problem is not in the high-voltage circuits. Further searches will be more difficult, evaluate your time and desire. If both are present, proceed to the third stage.
Stage three
Check if voltage is supplied to the ignition coil. This can be easily done with a tester, and if there is none, you can use an underhood lamp. However, you will need a pair of wires to connect it to the coil. The lamp must be connected between the "ground" and the input of the primary winding.
This note was copied from the resource RenaultBook.ru
At the third stage, as usual, there are also two possible options: voltage is either supplied to the coil or not. If it is supplied, the coil is to blame - a breakdown or short circuit, which, however, happens extremely rarely. The coil will have to be replaced. More often, there is poor contact in the connection of the wires to the coil. Or the same wet dirt, through which the spark flows away to an unknown destination. Sometimes the coil is polished to a shine, but underneath it there remains an invisible, very narrow strip of dirt - a good conductor.
If at the third stage you have made sure that voltage is not supplied to the coil, the fault lies with the electronics or contacts and unreliable connections in the low-voltage part of the ignition system. With electronics (switch and, less frequently, sensor in the distributor housing) you won't be able to handle it - you need special equipment to diagnose them. You can only tug on the sensor connector on the distributor housing - maybe it will help. The voltage on the connector contacts is only 12 V, so you can tug without fear. If voltage appears (when you pull the contacts the light blinks), restore everything that was unscrewed and disassembled, start the car and maybe you will still have time to do your business. If the engine does not start, but at least sneezes - unscrew the spark plugs and... (see above).
It may also happen that the entire ignition system has been checked, it is in order, but the engine, no matter how hard you try, still does not start. This means that there are problems with another of the systems mentioned earlier - the fuel system, that is, the supply of fuel to the engine.
If you have a car with injection (fuel injection system), do not touch it (the system). You can only come to the conclusion that it is the one that is faulty: there is a spark, the fuel is suitable - that means it is the one. Treatment only in a hospital. It is useless and even harmful to repair it at home or at artisans.
We have left a rare but most unpleasant diagnosis for last. If the starter works normally, and you have already spent a lot of time and made sure that the ignition and power supply are in perfect order, but the car still does not start, it is worth inspecting the camshaft drive belt. However, decide for yourself: this check can be carried out at the beginning, especially if the engine has traveled more than 60 thousand km. The difficulty is that you will have to remove or at least partially bend the upper part of the plastic or metal casing covering the belt. Perhaps the teeth of the belt are cut off (belts, like people, lose teeth from old age). In this case, the camshaft does not rotate and the engine will not work. It is clear that the toothless belt needs to be replaced. The belt replacement procedure is not complicated, but quite troublesome. It is carried out in a hospital. It is good if everything is limited to replacing one belt, and not bent valves or the entire cylinder head - this also happens.