Dan Ferrell écrit sur l'entretien et la réparation de voitures à faire soi-même. Il possède des certifications en technologie d'automatisation et de contrôle.
1. Batterie déchargée
2. Démarreur ou système défectueux
3. Alternateur défectueux
4. Filtre à carburant bouché
5. Régulateur de pression de carburant défectueux
6. Mauvaise pompe à carburant
7. Bobine ou module d'allumage défectueux
8. Capteur de position de vilebrequin ou capteur de position d'arbre à cames défectueux
9. Fuite de vide majeure
10. Courroie de distribution défectueuse
Plus loin dans cet article, nous vous aiderons à parcourir certains tests et à déterminer quel problème vous concerne afin que vous puissiez reprendre la route.
Votre problème rentre très souvent dans l'une de ces cinq catégories :
Lorsqu'il s'agit d'un moteur qui refuse de démarrer, vous pouvez utiliser les sons, ou leur absence, comme outil de diagnostic. Les sons vous aident à vous concentrer sur le système ou les systèmes où le problème pourrait être localisé, éliminant ainsi d'autres points problématiques potentiels.
Si vous entendez un seul clic solide lorsque vous essayez de démarrer la voiture, le problème peut provenir du démarreur ou du circuit.
Un bruit de cliquetis provenant de sous le capot lorsque vous essayez de démarrer le moteur peut indiquer une batterie sous-chargée, des bornes de batterie desserrées ou corrodées, ou un problème avec l'alternateur ou le système de charge.
Si vous n'entendez rien lorsque vous essayez de démarrer votre voiture, vérifiez :
Lorsque vous tournez la clé de contact pour démarrer le moteur, vous pouvez entendre le rugissement habituel du moteur, mais le moteur ne démarre jamais réellement. Si oui :
Si nécessaire, consultez les Ressources au bas de cet article pour obtenir de l'aide sur ces problèmes et d'autres.
Souvent, une condition de non-démarrage peut être attribuée à un défaut du système d'alimentation en carburant. Si votre moteur tourne mais refuse de démarrer, faites ce test simple. Ce test peut vous dire si le problème est lié à la livraison de carburant.
Si le moteur démarre pendant quelques secondes puis s'éteint, votre problème est probablement lié au carburant. Vérifiez le filtre à carburant, le régulateur de pression de carburant et la pompe à carburant, comme indiqué dans les sections suivantes.
La vidéo suivante vous montre comment utiliser le liquide de démarrage.
Maintenant que vous avez une idée du système à étudier, vous pouvez commencer à enquêter. Les dix sections suivantes traitent des dix défauts les plus courants auxquels vous êtes susceptible de faire face lorsque votre voiture refuse de démarrer, et de la manière de vérifier chaque défaut potentiel.
C'est l'une des raisons les plus courantes pour lesquelles une voiture ne démarre pas. Une batterie de voiture peut durer jusqu'à six ans, selon les conditions d'entretien et de fonctionnement. Des conditions météorologiques extrêmes, par exemple, réduiront sa durée de vie.
Cependant, il n'est pas rare qu'une batterie perde soudainement sa charge.
Vérifiez les connexions des bornes de la batterie. Retirez la corrosion et assurez-vous que les bornes sont bien serrées. Vérifiez ensuite le niveau d'électrolyte, si la batterie a des capuchons amovibles.
Lorsque votre voiture refuse de démarrer, assurez-vous que votre batterie est bien chargée. Vous pouvez utiliser un multimètre numérique (DMM) pour vérifier son état de charge.
Pour vérifier l'état de charge de la batterie :
Si vous avez besoin de recharger la batterie, utilisez une charge lente, si possible. Cela aidera à restaurer l'état de la batterie.
Votre magasin de pièces automobiles local peut vérifier si votre batterie est toujours en bon état.
Le démarreur et son circuit sont d'autres sources courantes de problèmes. Ce système pourrait être le coupable si vous entendez un clic solide lorsque vous essayez de démarrer le moteur.
Il pourrait y avoir un problème avec le solénoïde du démarreur, le relais ou le démarreur. Si nécessaire, vérifiez le circuit avec un test de chute de tension. Voir les Ressources au bas de cet article pour obtenir de l'aide sur ce test.
Also, your local auto parts store will check the starter motor for free, but you'll need to remove the starter from the vehicle.
Along with a dead or bad battery, alternator issues are one of the most common reasons for a no-start condition.
Usually, the charging system will turn on a warning light on the dashboard alerting you about a fault in the system. However, there are many reasons a charging system may fail to deliver a charge to the battery or electrical power to other systems in the vehicle.
Points to check:
Keep in mind that a corroded battery terminal could be a sign of an alternator overcharging the battery.
If you don't want to do it, your local auto parts store will check the alternator for you.
Most manufacturers recommend replacing the fuel filter every one or two years. Replace your fuel filter as recommended.
Although many fuel filters include a bypass valve in case the filter clogs, not all come equipped with this valve. Besides, rust and other sediments in the fuel tank can make their way to the fuel filter and clog its filter element.
Before giving out completely, a clogging fuel filter will give you one or more signs. For example, you may notice a lack of engine power at high speeds, difficulty starting the engine, or poor acceleration.
Check your repair manual to inspect the fuel filter and system in your particular model, if necessary.
If you suspect insufficient fuel reaching the injectors, do the quick fuel system delivery check as described in the second section of this post.
A fuel pressure regulator (FPR) limits the amount of pressure buildup in the system, typically to between 35 and 45 psi. Check your vehicle repair manual for your model specifications.
But FPRs can fail. If the internal diaphragm begins to leak fuel into the intake manifold, pressure will drop, and the cylinders will be flooded with fuel, making the engine hard to start.
Also, if too much raw fuel reaches the catalytic converter, the Check Engine Light (CEL) will begin to flash on your dashboard.
If you suspect insufficient fuel reaching the injectors, do the quick fuel system delivery check as described in the "Pre-Diagnostic 2" section of this article above.
You can perform a few FPR tests at home. See the Resources section at the bottom of this article for some help.
Fuel pumps have a long service life. They can last 80,000 miles or more. If your fuel filter and fuel pressure regulator are fine, but you have a fuel issue, probably your fuel pump is bad.
When turning the ignition key to the "On" position, before trying to start the engine, you should hear a buzzing sound for a couple of seconds. This is the sound of the fuel pump motor being activated to prime the fuel delivery system.
If you don't hear this sound, it may be that:
To verify a fuel delivery issue, do the quick fuel system delivery check as described in the second diagnostic section near the top of this article.
Also, check the repair manual for your particular model to see how to test the fuel pump, if necessary.
For the most part, ignition coils or modules are pretty reliable. Unlike spark plugs, wires, and distributor caps (depending on the model), an ignition coil or module doesn't require much attention.
However, they can fail from time to time. The conditions under which they operate, like heat, vibration and other engine performance issues, can have an adverse effect on any of these components after many miles of operation.
Older vehicle models used a single ignition coil and module to deliver a spark to the spark plugs. Newer models may use a module and one coil per spark plug. A failed coil or module in one of these models will certainly prevent the engine from starting.
You can use a spark tester to verify the presence and condition of the spark. You can buy one at your local auto parts store. If possible, get an adjustable spark tester you can use in different vehicles.
The Resources section at the bottom of this post, and your vehicle repair manual, can help you check an ignition coil or test for the presence of a spark in the ignition system.
The crankshaft position (CKP) sensor monitors engine speed, and the camshaft position (CMP) sensor tracks the position of the camshaft.
The electronic control module (ECM), the car's computer, uses the signal from both sensors to control fuel injection operation, direct ignition, and, depending on vehicle model, the variable valve timing system.
If any of these sensors fails, your car may fail to start.
Sometimes, depending on the specific fault, a bad CKP or CMP will trigger the check engine light (CEL). Whether the CEL illuminates on your dashboard or not, it's a good idea to scan the computer memory for potential diagnostic trouble codes (DTCs) that can help you diagnose a no-start condition.
If you don't have a scan tool, your local auto parts store may download DTCs for you without cost.
Also, check your vehicle repair manual. And, within the Resources section at the bottom of this post, you'll find links to other posts to help you check these sensors yourself, if possible.
Major vacuum leaks are not common, but they definitely happen. A vacuum leak can make the air-fuel mixture too lean, preventing the engine from starting.
A leak may come from a vacuum line, intake manifold gasket, throttle body gasket, leaking EGR valve gasket, power brake booster or positive crankcase ventilation (PCV) valve.
Vacuum leaks can be tricky to find. You can visually inspect every vacuum hose and trace it with your hand, feeling for tears or damaged spots. Also, pay attention to hissing sounds that may indicate a leak.
A leaking gasket is harder to detect, though, unless you have a smoke machine designed for this purpose.
Si nécessaire, consultez le manuel de réparation de votre véhicule.
You won't see this type of failure often. Timing belts can last between 50,000 and 100,000 miles or more, depending on your particular model. And if you have a timing chain rather than a belt, you may never have to worry about replacing it.
Still, if you've checked the usual suspect without success, check for a failed timing belt or chain.
The engine's crankshaft and camshaft are joined by a timing belt or chain through a series of sprockets. When this belt or chain brakes or wears out, or the tensioner fails, the crankshaft won't be able to rotate the camshaft anymore, making it impossible to start the engine.
Checking for a failed timing belt or chain:
On a vehicle fitted with a distributor, you can remove the distributor cap and try to fire up the engine. If the distributor rotor doesn't move, most likely your timing belt or chain, or one of the system components, has failed.
On models with multiport fuel injection systems, sometimes it's possible to remove the timing belt or chain cover to check for camshaft movement while trying to start the engine. Or you may be able to remove the oil cap from the valve cover, or the cover itself if necessary, to check for valve movement while trying to start the engine. If there's no movement, it's time to check the belt, chain, or system components.
If the camshaft rotates, you may still want to verify ignition timing. If the belt or chain has skipped some sprocket teeth, it may be difficult or impossible to start your engine.
Consult your vehicle repair manual to check crankshaft and camshaft synchronization.
Of course, there are other model-specific components or systems that can prevent your vehicle from starting. Par exemple :
Consult the repair manual for your specific make and model for help on these and other systems or components.
To sum up, when your car won't start, begin your diagnostic with the most simple components or obvious potential problems, as in Diagnostics 1 and 2 at the beginning of the article:
Then you can start checking the alternator, starter motor, ignition, fuel system pressure, and their circuits.
Most of the time you'll be able to fix the problem yourself. Sometimes, you will need to replace a fuel pressure regulator, ignition coil, module, or fuel pump, or fix a vacuum leak.
See the Resources below for diagnostic ideas if you have narrowed your problem down to a particular system.
This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional. 
Voici dix raisons pour lesquelles votre voiture ne démarre pas...
...Dans cinq catégories générales
Quelques recommandations avant de commencer votre diagnostic
Pré-diagnostic 1 :Utilisation du son comme outil de diagnostic
Quel son entendez-vous lorsque vous essayez de démarrer le moteur ?
Pré-diagnostic 2 :vérification rapide de la livraison du système de carburant
Maintenant :les dix défauts courants et comment les vérifier
1. La batterie est morte
2. Démarreur ou système défectueux
3. Faulty Alternator
4. Fuel Filter Clogged
5. Faulty Fuel Pressure Regulator
6. Bad Fuel Pump
7. Faulty Ignition Coil or Module
8. Faulty Crankshaft or Camshaft Position Sensor
9. Major Vacuum Leak
10. Failed Timing Belt
A Few Unusual Additional Possibilities
Dealing With a Car That Won't Start
Resources on Starting System Faults
Car starter problems? Don't blame the starter motor yet. These 5 troubleshooting tips will help you find the culprit.
Testing the voltage drop can help you find trouble spots in your starter circuit before you swap components unnecessarily.Resources on Charging Circuit Faults
Diagnose alternator and charging system problems with this practical guide to get your car back on the road faster.
Voltage-drop test your charging system circuit before condemning your alternator.Resources on the Fuel System
Learn how to test a fuel pressure regulator to save money and time in car repairs.Resources for Dealing with the Crankshaft and Camshaft Sensors
Troubleshoot an inductive or Hall effect type crankshaft position (CKP) sensor using a digital multimeter.
You can do a camshaft position sensor test using a digital multimeter at home and, if necessary, using a few common tools.
If your car’s ignition system has no spark, a few simple tests can help you locate the fault.Resources for Dealing With Battery Faults
This guide will show you how to use a digital multimeter, hydrometer, and other simple tools to troubleshoot, inspect, and clean your battery if necessary.
Find that parasitic battery drain that's causing your car battery problems whether you have a newer or older vehicle model.
