Why Won't My Car Start? 7 Common Causes and How to Fix Them

Have you ever turned the key in your car's ignition only to be met with an awful silence? Few things are more frustrating than a car that refuses to start properly. But don't panic yet - there are a handful of common issues that could be preventing your car from starting. Read on to learn about the 7 most common reasons your car won't start along with steps you can take to get your vehicle back up and running.

Dead or Faulty Car Battery

The most common cause of a no-start condition in your car is a dead or dying battery. Your car battery is responsible for providing the initial jolt of electricity to the starter motor which then powers up the engine. If the battery charge is weak, your car simply won't have the electrical current to get the engine cranking.

Some of the most common symptoms of a dead battery include:

  • Dim or no interior lights when you turn the key.
  • Lack of any noise from the starter motor. Usually, you'll hear a clicking or whirring sound as the starter spins.
  • Very sluggish cranking that seems to take more effort than usual. The engine may even turn over slowly or not at all.

If you suspect a dead battery, the first thing to check is the battery terminals and connections. Look for any corrosion on the battery posts and cable clamps which can prevent a solid connection. Use a wire brush to clean off any stubborn buildup. Make sure the cable connections are tight as well.

Wiggling battery cables back and forth can scrape away corrosion underneath and restore contact. You can also try giving the battery a gentle tap or two with a rubber mallet to jar things back in place.

If cleaning the connections doesn't work, it's time to test the battery itself. Most auto parts stores will do this for free. They'll attach a diagnostic machine to measure the battery's state of charge and also test its ability to hold a charge.

If the battery tests bad, the only solution is to replace it with a new one. Today's car batteries typically last 3-5 years, so you may simply be due for a fresh battery if yours is older. Extreme hot or cold temperatures can also shorten battery life.

Other common causes of a dead battery include:

  • Accidentally leaving the headlights or interior lights on overnight which drains the battery.
  • A bad alternator that fails to recharge the battery as you drive. We'll cover alternators more in the next section.
  • Parasitic drains from accessories improperly wired to stay on even when the car is off.
  • Normal deterioration due to the battery's age. They lose capacity over years of use.

If you need to replace your car battery, buy one with the same specifications as your original battery which can be found in the owner's manual or printed on the battery label. Installing a new battery is straightforward - just swap the cable connections over to the corresponding positive and negative posts.

Many batteries today are maintenance-free and don't require you to check fluid levels. But if you do have an older-style battery with removable caps, make sure the fluid covers the internal lead plates before installing it in your car. Top off with distilled water if needed.

With a freshly charged or brand new battery installed, your car should have no trouble turning over the starter and engine. If it still won't start, you'll need to move down the checklist to the other troubleshooting steps below.

Bad Alternator

The alternator in your vehicle has one main job - to recharge the battery while the engine is running. It generates electricity that replaces the power drained by the starter motor during cranking as well as powering the ignition system, lights, accessories, and computer while driving.

If the alternator fails, the battery won't get recharged. And if you drive your car for an extended time without a functioning alternator, the battery will completely drain leaving you stranded.

Signs of a bad alternator include:

  • Dimming headlights at idle or while driving. As the alternator fails, it doesn't send enough voltage to fully power all the electronics.
  • Dashboard warning lights indicating a battery or charging system issue.
  • The battery itself frequently dying since it's not getting recharged.

Alternators tend to fail after many years and miles of service, though premature failure can happen as well. If you suspect a bad alternator, have it tested at an auto parts store or repair shop. They'll use specialized diagnostic equipment to check if the alternator is generating adequate amperage.

Replacing a bad alternator with a new or rebuilt one is the fix here. Make sure to get one with the same amperage rating as your original. Many are relatively easy to replace by simply unbolting the old one and installing the new alternator. The battery positive and negative cables also have to be transferred over to the back of the new alternator during installation.

If you'd rather not tackle this repair yourself, any auto repair shop can swap out a bad alternator. The average alternator replacement cost is $400-600 for parts and labor which is money well spent to get your charging system working properly again.

Driving your car without fixing a bad alternator risks leaving you stranded when the accessories and engine shut off from lack of electrical current. It could also cause expensive damage to the battery and other systems from an insufficient power supply.

Faulty Starter Motor

When you turn the ignition key to start your car, it's the starter motor that spins the engine to get it running. This small but powerful electric motor relies on the battery to provide the initial kick of energy needed to engage the flywheel and crank the engine.

If the starter motor itself is having problems, your engine simply won't turn over despite the battery being charged. Some common symptoms of a bad starter motor include:

  • Nothing happening when you turn the key. No starter engagement at all.
  • A single click or clunk but no cranking. This indicates the starter solenoid is trying to operate but the motor isn't turning.
  • Grinding or whirring noises from the starter. This points to worn starter gear teeth.
  • The starter spins but cranks weakly. Extended cranking could indicate commutator or brush issues inside the motor.

Like most electrical components, starter motors wear out over time from normal use. High mileage, hot operating temperatures, and damage from backfiring engines can also contribute to their failure.

If you suspect starter trouble, begin by checking all the wiring connections to the motor itself including the heavy power cables as well as the smaller control wires. Loose or corroded wires are a common cause of no-crank conditions.

You can also try tapping on the starter motor with a wrench or hammer while someone else turns the ignition key. This can jostle its internal parts and make contact if the issue is merely stuck brushes or loose windings.

Otherwise, the starter will need to be tested at a repair shop to properly diagnose it. If confirmed bad, replacement with a new or rebuilt starter is required. Shop around for the best deal as prices can range widely from 200 up to 500.

And be aware that starter replacement often requires supporting labor to disassemble surrounding components for access which adds to the overall cost.

Ignition Switch Failure

The ignition switch in your vehicle controls the electrical flow from the battery to the starter motor and ignition system. When you insert the key and turn it to the Start position, it engages these critical components to enable engine cranking.

A faulty ignition switch manifests in fairly straightforward symptoms - nothing at all happens when you turn the key. And this will occur whether the battery is good or not. Common causes include:

  • Mechanical wear inside the ignition switch itself. The contacts simply cease to make proper electrical contact.
  • External damage to the switch housing which knocks things out of alignment internally.
  • Failed wiring from the switch to the starter motor or ignition system.

Start by jiggling your key back and forth in the ignition and trying to turn it to the Start position again. This may temporarily reconnect worn internal components. Spraying a contact cleaner like WD-40 into the ignition switch can also help clean things up.

If the ignition switch is confirmed to be bad, replacement is required. The switch housing itself is usually fairly affordable, costing $50 or less. However, installation labor can be intensive depending on the vehicle. The steering column area often has to be disassembled to access the switch.

In some cases, the ignition lock cylinder where you insert the key can fail instead of the switch itself. This locks up the ability to turn the key. A locksmith may be able to repair it, but replacement of the entire cylinder is often the better solution.

Fuel System Problems

Of course, a car needs proper fuel supply in order to start the engine. Any issues with the fuel delivery system can lead to a no-start. Some of the most common fuel-related causes include:

  • A clogged fuel filter preventing adequate fuel flow to the engine.
  • A failing fuel pump not supplying enough fuel pressure for injection or carburation.
  • An empty or near-empty fuel tank. Make sure you have at least a quarter tank of gas.
  • Dirt or water in the gas tank gumming up the fuel lines and injectors.
  • Faulty fuel injectors not spraying properly.
  • Vacuum leak in the fuel pressure regulator or along the fuel rail.

Start by checking your fuel level - it's easy to overlook running out of gas as the reason your car won't start. Also listen for the in-tank fuel pump buzzing when the key is first turned. No sound could mean a bad pump.

You can test fuel pressure right at the fuel rail to check for adequate volume and pressure. If it's lower than specifications, the filter, pump or a line could be obstructed.

Any parts of the fuel system like pumps, filters or injectors may need cleaning or replacement to restore proper fuel delivery. Diagnosing issues precisely requires electrical testing of components and fuel rail pressures.

While troubleshooting fuel problems is often left to professional mechanics, you can inspect and change the fuel filter yourself as a first step. Use caution when working on fuel systems to avoid spills or sparks.

Electrical and Wiring Gremlins

Like any complex electronic device, vehicles have miles of wiring and hundreds of connections that have to be maintained in good working order. Corrosion, loose plugs, and bare wires can all contribute to electrical faults that prevent starting.

Check for the simplest issues first like blown fuses or a tripped main battery cable fuse in the fuse box under the hood. Reset any breaker or replace blown fuses with the same amperage rating as indicated on the fuse box lid.

Inspect wiring harnesses leading to engine components for chafed insulation or green corrosion buildup on terminals. Clean any corrosion with electrical contact cleaner or fine sandpaper. Cover bare wires with electrical tape as a temporary fix.

Intermittent electrical faults are harder to track down. They may take jiggling wires or even slamming doors to reproduce the symptom. It pays to thoroughly examine the wiring related to the ignition, fuel and starting systems first if you suspect this type of issue.

An onboard diagnostic scan tool that reads engine computer fault codes can provide useful direction for electrical issues. Auto parts stores will often scan codes for free to help you pin down problems.

Mechanical Timing Issues

The precise mechanical timing of internal engine components is critical for the engine to start and run properly. Problems with the timing belt, timing chain, crankshaft position sensor, camshaft or valves can all prevent successful cranking.

Symptoms may include the engine turning over but not actually starting or extremely rough running if it does fire up. You may also notice loud rattling or clattering noises from the front of the engine pointing to timing component failures.

Diagnosing mechanical timing problems requires a professional technician to inspect the intake/exhaust valves, timing chain or belt, gear assembly and related components. Repairs can become complex and expensive depending on the specific parts that need replacement.

But address these issues promptly since severe engine damage can occur when timing components fail and the valves and pistons collide. In some cases, the motor may need to be disassembled and rebuilt.

When to Call a Mechanic

While the checklists above can help you troubleshoot and even fix some no-start problems yourself, there are times when it pays to hand things over to a professional mechanic, especially for potentially complex or hazardous repairs.

See a mechanic promptly if:

  • You've checked the obvious issues like battery, fuses, connections but the car still won't start.
  • The engine cranks over but simply won't run even with fuel and spark present.
  • You need engine timing diagnostics or other internal repairs.
  • Fuel pressure testing or injector service is required.
  • The starter or alternator tests bad and needs replacement.

Repair shops have specialized diagnostic tools and the expertise to troubleshoot even tricky no-start conditions efficiently. Plus they can handle any necessary repairs safely.

While their labor rates may be higher than DIY repairs, you are paying for their experience and ability to get your car back on the road quickly with no trial and error on your part.

For complex issues like internal engine repairs or electrical faults, attempting to fix it yourself without proper knowledge can sometimes make the problem worse and more expensive in the long run.

The money spent on professional diagnosis and repairs is also often less than the cost of a tow truck plus any missed time at work from being stranded.

Don't ignore a no-start situation. The sooner you can diagnose the cause and make needed repairs, the less risk you run of being left with an unusable vehicle or compounding damages from continued failed start attempts.


When your car won't start properly, it's incredibly frustrating but also often fixable with basic troubleshooting. Check for simple issues like battery charge and loose connections first before moving to more complex diagnostics.

In many cases, you can resolve starter motor, alternator, ignition switch and even some fuel delivery problems yourself with some DIY repairs. But be ready to hand it over to a professional mechanic for potentially intensive repairs related to internal engine components or difficult electrical faults.

Catching and correcting minor issues promptly will keep your car starting reliably for years to come. Don't hesitate to replace worn parts like the battery, starter and alternator that naturally degrade over time.

With some persistence and diligence, you can usually get to the bottom of why your car won't start and have it running like new again. Just be sure to stay safe while troubleshooting fuel systems, batteries, electrical wiring and other components.