The most common reasons your car won't start, and how to tell which one you have
When your car won't start, the problem is almost always one of three things: a dead or weak battery, a faulty starter motor, or a fuel system issue. You can narrow it down in seconds by listening to what happens when you turn the key. If you hear rapid clicking sounds, the battery is too weak to turn the engine over. If you hear nothing at all—no clicking, no cranking, just silence—the problem is usually the starter or a broken electrical connection. If the engine cranks but won't catch and run, the fuel pump or ignition system is likely at fault.
The battery is by far the most common culprit, especially if your car has been sitting unused, if you left lights on overnight, or if the battery is more than three to five years old. A starter motor fails less often but becomes more likely as your car ages. Fuel system problems are less common in newer cars but can happen at any age.
Key Takeaways
- Rapid clicking when you turn the key points to a dead or weak battery; silence points to a starter or electrical connection problem.
- A jump start can restore a weak battery temporarily, but a battery that is more than three to five years old will need replacement.
- If jump-starting does not work, the starter motor or fuel pump is likely faulty and requires a mechanic to diagnose and repair.
- Leaving lights on, extreme cold, and age all drain or damage batteries; keeping jumper cables or a portable jump box in your car can get you moving again quickly.
How to jump-start your car safely
A jump start works by using another car's battery to supply power to yours. You will need jumper cables (heavy-gauge wires with clamps on both ends) and another vehicle with a working battery. Park the working car close to yours, turn off both engines, and open both hoods.
Attach one red clamp to the positive terminal of your dead battery (marked with a + sign), then attach the other red clamp to the positive terminal of the working battery. Attach one black clamp to the negative terminal of the working battery (marked with a − sign), then attach the final black clamp to an unpainted metal surface on your engine block—not the negative terminal of your dead battery. This last step prevents sparks near the battery. Start the working car and let it run for two to three minutes, then start your car. Once both engines are running, remove the clamps in reverse order: black from your car, black from the working car, red from the working car, red from your car.
Drive your car for at least twenty minutes to recharge the battery. If the engine dies again within a few hours, the battery itself is failing and needs replacement, not just a charge.
When the battery is the problem
A battery that is three to five years old or older will eventually fail, especially if your car sits unused for long periods or if you live in a very cold climate. Cold weather drains battery power faster because the chemical reaction inside the battery slows down. A battery that is only two years old but has been drained completely—by leaving headlights on all night, for example—may recover fully after a jump start and a good charge.
To know whether your battery needs replacement, look at the date code printed on the battery case itself. Most batteries are marked with a letter and number showing the month and year of manufacture. A battery that is more than five years old should be replaced even if it starts your car today, because failure becomes unpredictable. If your battery is younger but has failed once, a mechanic can test it with a load tester to see whether it holds a charge or is truly dead.
Battery replacement costs between $100 and $300 depending on your car's make and model and the type of battery. Many auto parts stores and repair shops will install a new battery for you on the same day you purchase it.
What to do if jump-starting does not work
If your car still will not start after a successful jump start, or if it will not start even with jumper cables attached, the problem is not the battery. The starter motor—the electric motor that turns the engine over—is the next most likely culprit. A failing starter usually makes a grinding or whirring sound when you turn the key, or it may make no sound at all even though the battery is clearly working (you can tell because your lights and radio come on).
A faulty starter requires a mechanic to replace. Starter replacement typically costs between $300 and $500 in labor and parts, though the exact price depends on your car's make and model. Some cars have the starter in an straightforward-to-reach spot; others require removing other engine components first, which adds time and cost.
If the engine cranks but will not catch and run, the problem is likely the fuel pump, fuel filter, or ignition system. These problems also require a mechanic's diagnosis and repair. Do not attempt to fix these yourself.
Preventing a dead battery
The easiest way to avoid a dead battery is to turn off all lights and electronics before you leave your car. Check that your headlights, interior lights, and radio are off. If your car has automatic headlights, make sure they are set to turn off when the engine shuts down, not to stay on indefinitely.
Keep your battery terminals clean and free of corrosion. If you see a white, blue, or green crusty buildup on the battery terminals, disconnect the negative cable and scrub the terminals with a wire brush and a mixture of baking soda and water. Reconnect the negative cable when you are done. Corroded terminals can prevent the battery from charging properly even when the alternator is working.
Keep jumper cables or a portable jump box (a small battery pack designed to jump-start a car) in your vehicle. A portable jump box costs between $50 and $150 and does not require another car to use. If you live in a cold climate, park in a garage if you can, because cold dramatically reduces battery power.
When to call a tow truck instead of trying to fix it yourself
Call a tow truck if you have tried jump-starting twice and the car still will not start, or if you do not have access to jumper cables and another vehicle. Towing costs between $75 and $150 depending on the distance and your location, but it is cheaper than damaging your car by trying to force-start it or by driving it to a repair shop when something critical is broken.
If your car starts but dies when ready, or if it starts and then dies repeatedly, do not drive it on the highway. Drive slowly to the nearest repair shop, or call a tow truck. Repeated stalling can mean a fuel pump failure or an electrical problem that could leave you stranded in traffic.
Frequently Asked Questions
Can I start my car by pushing it downhill or bump-starting it?
Bump-starting (rolling the car to build momentum and then releasing the clutch to turn the engine over) works only on manual-transmission cars and only if the battery has enough power to run the ignition system. It will not work if the battery is completely dead. Modern cars with automatic transmissions cannot be bump-started. Jump-starting is faster and safer.
How long does a car battery last?
Most car batteries last three to five years. Cold climates, frequent short trips, and leaving electronics on all shorten battery life. You can extend battery life by keeping the terminals clean and making sure the alternator is charging the battery properly. Have your battery tested annually after it reaches three years old.
What does it mean if my car makes a clicking sound but will not start?
Rapid clicking almost always means the battery is too weak to turn the engine over. Try a jump start. If the clicking continues after a jump start, the battery itself is failing and needs replacement. Slow, single clicks usually point to a starter problem instead.
Can a dead battery damage my car's computer or electronics?
A dead battery will not damage your car's computer or other electronics. However, jump-starting incorrectly—by connecting the cables in the wrong order or by connecting the negative clamp to the dead battery instead of the engine block—can cause electrical damage. Follow the correct order: red to dead battery, red to working battery, black to working battery, black to engine block.
Is it safe to jump-start a car in the rain?
Jump-starting in light rain is safe as long as you keep the battery terminals and clamps dry. Avoid jump-starting in heavy rain or a thunderstorm. If water gets inside the battery or onto the terminals while the clamps are attached, it can cause a short circuit or spark. Wait for the rain to lighten, or call a tow truck.