14 Reasons Your Car Won't Start

Nothing makes your stomach turn over faster than when your engine fails to start. There are few things in life more worrisome than when your car won’t start, as your mind begins to stress about the cost of repairs and when you’ll have your vehicle back on the road. 

Based on what our roadside assistance teams have seen over the last 100 years of helping stranded motorists, we’ve listed the most frequent reasons a car won’t start and how to recognize the root of the problem. We aren’t stopping there — we’ve also included ways to troubleshoot so you can quickly and safely get back on the road and included the average cost of repairs so you know what to expect.

It should be noted that the reasons included here are for vehicles with combustion engines as opposed to electrical or hybrid cars, which may not start for different reasons.

Most of the reasons a car won’t start are related to one of the following auto systems:

1. Electrical
2. Fuel
3. Engine
4. Anti-theft and safety

Since the electrical system has the most potential for problems, you may want to start there before moving onto other systems.

1. The Battery Is Dead or Dying

The most common reason your car won’t start is the battery, so check it first.

What it does: A car battery initiates the car’s electrical system by sending a jolt of electricity to the starter, which starts the engine.

How to tell if it's the battery:

• The dashboard lights are dim.
• Radio goes in and out.
• The battery terminal is corroded.
• It’s been awhile since you replaced the battery — most batteries last an average of three to five years.
• The battery appears swollen. (If you notice this, call roadside assistance for a tow to a repair facility. Do NOT attempt to jump start a swollen battery — it could burst, spraying battery acid on anyone near the battery.)
• You smell rotting eggs from the engine.
• You either hear a clicking or don't hear a sound when you turn the key.

What to do:

1. Try jumping your car. If it starts, drive to your auto repair shop or auto parts store to get a replacement immediately.
2. Call roadside assistance. Since you won’t be able to start the car, you’ll need a tow to an auto repair shop. If you are a AAA member, our roadside assistance team will try jumping your vehicle for you, and if it still doesn't start, we’ll replace it on the spot or tow you to the nearest auto repair shop.

Average repair cost: This service costs $50 to $200 (varies based on the make and model of the car, battery size and brand) plus labor costs.

2. The Alternator Has Gone Bad

The second most common reason a car won’t start is a bad alternator. Once you’ve ruled out the battery as the problem, check your alternator.

What it does: The alternator recharges the battery after it delivers the charge to start your car. It also keeps all the electrical systems running once your car’s engine is running.

How to tell if it’s the alternator:

• Interior lights are dimmer than usual.
• Headlights are either dim or overly bright.
• A growling noise comes from under the hood.
• You smell burning rubber coming from under the hood.
• The car starts but immediately dies.

What to do:

1. Test the alternator with a multimeter. To do this, you’ll need to start the car and check the battery’s voltage, which should be 13-14.5 volts. If it’s outside that range, your alternator is either undercharging or overcharging your battery and needs to be replaced.
2. Call roadside assistance. If the alternator is dead, you can’t start your car without replacing it, so you’ll need to tow it to a nearby auto repair shop.

Average repair cost: This repair costs $100 to $350 depending on the model of alternator your car needs plus labor costs.

3. The Starter Is Faulty

Once you’ve ruled out the battery and the alternator, it’s time to investigate the next major element in the electrical system: the starter.

What it does: The starter spins the engine’s flywheel, which initiates the combustion process of mixing air, fuel and ignition inside of the engine’s cylinder chamber. It engages when you start the car by turning the key or pressing the engine start button.

How to tell if it’s the starter:

• Before the starter fails completely, you may notice:
  • The car struggles to crank when you turn the key/press the start button.
  • The starter continues to keep running after you release the key.
• Once the starter fails:
  • You hear a crank with a groaning noise when you turn the key.
  • The interior lights dim/flicker when you try to start the car — the starter is drawing additional power from wherever it can.
  • The starter system is covered in oil. Check your owner’s manual for the location of the starter.
  • After multiple attempts to start the car, you notice smoke or a burning smell coming from under the hood.

What to do:

1. Try jump-starting your car. Sometimes the added voltage from a jump start can be enough to engage the starter. If you can get it started, drive straight to an auto repair shop for a replacement since there’s no guarantee a jump start will work again.
2. Call roadside assistance. If the car doesn’t start when you jump it, you’ll need a tow to an auto repair shop so they can replace the alternator for you.

Average repair cost: This repair costs $80 to $350 depending on whether you need to replace a starter component or the entire system plus labor.

4. The Ignition Switch Is Jammed or Broken

The starter may not work because there’s something wrong with the ignition switch. Unfortunately, it can be hard to diagnose since the switch fails slowly over time and you experience intermittent trouble starting your car.

 What it does: The ignition switch relays the signal between your key and the starter.

How to tell if it’s the ignition switch:

• Your key won’t turn at all or is challenging to turn.
• The engine may not crank, or it starts and immediately stalls.
• Other electrical systems may not work at times.
• Your car stalls while driving.

What to do:

1. Drive to your auto repair shop. If your car is drivable, take it to your auto repair shop immediately to avoid it stalling out on the road, which can be dangerous.
2. Move your car to safety and call roadside assistance. If your car stalls out while driving it, coast to safety on the side of the road before calling for roadside assistance for a tow.

Average repair cost: This repair costs $108 to $131 plus labor costs.

5. The Spark Plugs Are Old or Dirty

Old or dirty plugs are another common culprit when your car doesn’t start.

What it does: Spark plugs trigger the combustion of the fuel and air combination in your engine.

How to tell if it’s the spark plugs:

• The engine starts sluggishly.
• The engine sounds strange (uneven, rough) while running.
• You feel vibrations when your car is idling.
• You notice sluggish acceleration.
• You notice decreased fuel economy.
• The engine misfires, which means it temporarily fails. 
• You may notice temporary power loss or unusual vibrations while the engine is running.
• You hear a knocking sound while the engine runs.

What to do:

1. Purchase spark plugs and swap them out yourself. The labor can often cost more than the spark plugs themselves!
2. Call roadside assistance. If you can't start your car or replace the spark plugs, you’ll need a tow to the nearest auto repair shop.

Average repair cost: This repair costs $16 to $100 for a set, depending on the type and number of spark plugs you need, plus labor costs.

6. There’s a Problem With the Ground Cable

If you haven't driven your car in a while, critters may have gotten under the hood and nibbled on your ground cable. But if that isn’t the case, it can be harder to diagnose a ground cable issue since many of the symptoms occur randomly.

What it does: The ground cable connects the negative terminal of the battery to the car’s metal frame, completing the electrical circuit.

How to tell if it’s damaged wiring:

• Electrical systems such as the AC, interior lights, radio, or others randomly fail.
• You smell burning.
• You see visibly damaged wire when you look at the ground cable.
• You see corrosion on the negative terminal of the battery.
• You check the ground wire with a multimeter.

What to do:

1. Replace the ground wire yourself. The hardest part of repairing a ground wire is ensuring that’s the reason your car won’t start. If you are sure it’s the ground wire, purchase the length of wire you need from your auto parts store and replace it yourself.
2. Call roadside assistance. If you aren’t sure the ground wire is the problem, or if you don’t feel comfortable changing it yourself, call roadside assistance to tow your car to the nearest auto repair shop.

Average repair cost: This repair costs $307 to $333 plus labor costs.

7. Your Car Has a Blown Fuse

Fuses are a key part of your car’s electrical system — if they blow, they can shut down the car’s entire electrical system.

What it does: A fuse protects the electrical circuit and the components within that specific system. If an electrical short or an electrical surge occurs, the fuse will “blow” to protext the system and its components from further damage.

How to tell if it’s a faulty fuse:

• Your engine stalls while you are driving.
• Your engine won’t start when you turn the key.
• The fuel pump is silent while you try to start the car.
• The check engine light is on.
• Acceleration is inconsistent while driving.
• You see a gap in the wire within the fuse or a dark smear on the fuse’s casing.

What to do:

1. Replace the fuse. If you can locate the fuse yourself, you can replace it on your own. Since labor costs can be more expensive than the fuse itself, purchasing the appropriate fuse at your auto parts store can save you money. Once you’ve replaced the fuse yourself, take your car to an auto repair shop to have them determine what caused the fuse to blow. You may have a more significant issue that may result in another blown fuse.
2. Call roadside assistance. If you have a blown fuse, there’s nothing you can do to override it, so you’ll have to get a tow to your nearest auto repair shop.

Average repair cost: Replacing the fuse costs $10 to$ 20 plus labor costs, but the cost to correct the problem that caused the fuse to “blow” depends on the problem.

8. Your Car Doesn’t Have Enough Gas

If your car’s electrical system functions as it should, the next step is to start looking at your fuel system. First, check if you have enough gas to start the car.

What it does: Spark plugs ignite the gas and air in the engine, creating the energy needed to turn the pistons in the engine.

How to tell if there’s not enough gas:

• The gas light is illuminated on the dashboard.
• The fuel gauge is empty.
• The car stalls out while you are driving.
• The car turns over but won’t start.

What to do:

1. Move your car to safety. If your car ran out of gas while you were driving, coast to the shoulder or another out-of-traffic spot. 
2. Walk to a nearby gas station to purchase gas. If you can do so safely, walk to a nearby gas station. You should be able to buy a gas can, which you can fill with enough gas to get you to a gas station. (Don’t overfill the can as it may be too heavy to carry back to your car.)
3. Call a friend to bring you gas. If you can’t walk to the station yourself, call a friend or family member for help. They can pick up gas for you and deliver it.
4. Call roadside assistance. Roadside assistance can tow you to the nearest gas station so you can fill your tank. If you are a AAA member, a roadside assistance team member will bring you enough gas to get to the nearest gas station. (Let them know if you need diesel when you call.)

Average repair cost: This repair will cost the cost of gas plus the cost of a local towing service.

9. The Fuel Filter Is Clogged

If you have enough gas, the fuel filter could be clogged and blocking fuel from your engine.

What it does: The fuel filter removes particles from the gas in your tank to protect the engine. Over time, those particles can clog the filter to the point that gas can no longer travel through it.

How to tell if it’s the fuel filter:

• You hear a loud whining noise in the fuel tank.
• The car struggles to start, but you hear a normal cranking sound.
• The engine sputters and stalls after starting.
• You lose power when traveling at high speeds, up steep inclines or towing a heavy load.
• You notice decreased fuel efficiency.

What to do:

1. Replace the fuel filter yourself. You can save money on labor costs by purchasing the appropriate fuel filter for your vehicle from your auto parts store. Your local auto parts store can look up the proper part your car needs. 
2. Call roadside assistance. If you can’t replace the filter on your own, you’ll need to have your car towed to a nearby auto repair shop so they can replace the filter for you.

Average repair cost: This repairs costs $10 to $70 plus labor costs.

10. The Fuel Pump Relay Failed

If your filter is clear but you're still having issues with fuel, the fuel pump may not be functioning properly. 

What it does: The fuel pump relay is the switch that controls the fuel pump. If the pump receives too much power, the relay will break and the fuel pump will be unable to function until it is replaced. There are also moving parts in the relay that can break down over time.

How to tell if it’s the fuel pump:

• The car struggles to start, especially when the engine hasn’t run in a while.
• The engine cranks but doesn’t start.
• The battery drains quickly — even when it’s new.
• The car stalls while driving.
• A multimeter reveals the fuel pump relay is not transmitting power.

What to do:

1. Replace the relay yourself. If you’ve confirmed the fuel pump relay is the problem, it’s relatively easy to replace yourself. Since labor costs for this repair are often more than the part itself, purchase one from your local auto part shop and replace it yourself.
2. Call roadside assistance. If you can’t replace the relay on your own, you’ll need to have your car towed to an auto repair shop.

Average repair cost: This repair costs $35 plus labor costs.

11. The Timing Belt Is Worn Out

If you’ve ruled out the electrical and fuel systems as the source of the problem, have your timing belt inspected.

What it does: The timing belt turns the camshaft in the engine, which opens and closes the engine’s valves. The timing belt ensures this happens in time with the crankshaft.

How to tell if it’s the timing belt:

• There’s a ticking noise from the engine when it’s running.
• You hear a quick crank with a spinning sound when you try to start the engine.
• You see oil leaking near the motor.
• The exhaust is smokier than usual.
• The car’s RPMs are not functioning normally.
• The car stalls while driving or won’t start at all.

What to do:

1. Take your car to an auto repair shop. A worn-out timing belt can break while you are driving, stopping your engine abruptly and stranding you in traffic. It can also seriously damage your engine when it breaks, so it’s best to take your car in for repairs as soon as you notice signs of a worn-out timing belt.
2. Call roadside assistance. If your timing belt breaks while you are driving, move your car safely to the side of the road and call roadside assistance to get a tow to the nearest repair shop.

Average repair cost: This repair costs $367 to $585 plus labor costs.

12. The Steering Lock Is Engaged

Modern cars come with sophisticated anti-theft and safety sensors, but sometimes they can malfunction and prevent the car from starting. 

What it does: A lock within the steering column prevents the steering wheel from moving without the key in the ignition or a signal from your key fob.

How to tell if the steering lock is engaged or faulty:

• The steering wheel tilt feature won’t lock.
• The steering wheel doesn’t turn as smoothly as usual.
• You hear a clicking or grinding sound from the steering column while driving.
• The steering wheel doesn’t return to zero degrees after a turn.

What to do:

1. Wiggle the steering wheel gently when the key is in the ignition. Sometimes the steering lock gets stuck, and wiggling the wheel can disengage it.
2. If you have a key fob, check the battery. If you can’t disengage the steering lock by wiggling the wheel, or if you have a key fob, check the battery. The signal may be too weak to disengage the steering lock.
3. Call roadside assistance. AAA’s roadside assistance team can tow your vehicle to an auto repair shop so they can replace your steering lock.

Average repair cost: This repairs costs $100 to $300 plus labor.

13. The Key Fob Battery Is Dead or Dying

Key fobs are so convenient that most modern cars have them as a standard feature. Unfortunately, they can malfunction.

What it does: All key fobs transmit a signal to your car. When your car receives that signal, you can unlock the doors or open the trunk. Some key fobs also allow you to start the engine with a button push rather than inserting a key. These fobs act as an anti-theft device, preventing the engine from starting if the car doesn’t sense the key fob.

How to tell if it’s the key fob battery:

• You must be right next to the car to unlock it with the key fob.
• It takes more than one click on the key fob to unlock the doors.
• The key fob inconsistently fails to unlock the doors.
• The car makes no noise when you try to turn it on, but the electrical systems, like the interior lights or the radio, come on.

What to do:

1. Replace the key fob’s battery. Most key fobs use a button cell battery, which you can buy in most grocery or hardware stores. You’ll find the size written on the battery. The most common battery sizes are:

• CR2032
• CR2450
• CR1616
• CR2016

1. Use a spare key. If you have a spare key, you can use that until you can replace the battery. Check your key fob — some contain a hidden key!
2. Replace the key fob. If you replace the battery and the key fob still doesn’t work, something may be wrong with the transmitter. Take your key fob to the dealership, where they can run diagnostics on the system. They will determine the problem and possibly order you a new key fob, which will need to get connected to your vehicle.

Average repair cost: This repair costs $5 for a new battery or $50 to $500 for a new key fob.

14. The Car Isn’t in Park or Neutral (Or the Neutral Safety Switch Is Faulty)

Finally, your vehicle may be in the wrong gear (or think that it is).

What it does: The neutral safety switch senses whether the car is in park or neutral. If it’s not, the switch won’t allow the vehicle to start to prevent it from jumping forward or reversing as soon as the engine starts.

How to tell if the car is in the wrong gear or the neutral safety switch is faulty:

• Wrong Gear:
  • Look at your gearshift to see what gear you’re in.
  • If the dashboard lights are on, look at the gear indicator to see what gear you are in.
• Failed neutral safety switch:
  • The check engine light is on.
  • The engine starts in park but not neutral or neutral but not park.
  • The engine doesn’t start at all
  • The gear on the dashboard and the shifter don’t match.
  • The reverse lights don’t turn on when the car is in reverse.

What to do:

1. Shift into park or neutral. If your manual car is in the wrong gear, push the clutch pedal and shift into park or neutral.
2. On a manual car, move the shifter through different gears while attempting to start the car. If the vehicle starts in any gear other than park or neutral, make an appointment at your auto repair shop to get the neutral safety switch replaced.
3. Try to start the car while wiggling the gearshift. With the car in park, gently wiggle the gearshift while you try to start the car but don’t push it into another gear. If the neutral safety switch is loose, wiggling it may activate the switch so the engine can start.
4. Call roadside assistance. If you can’t get the car started, call roadside assistance so they can tow it to the nearest auto repair shop for a replacement.

Average repair cost: $100 to $300 plus labor costs to replace the neutral safety switch.

Call AAA Roadside Assistance When Your Car Won’t Start

Take a few minutes to become a AAA member today! If your car doesn’t start, our roadside assistance team may be able to solve the problem on site (if you need a jump or a new car battery, for example) or tow you to the nearest auto repair shop.

All AAA approved auto repair facilities employ Automotive Service Excellent (ASE) certified or factory-trained technicians, so you can trust you’ll get the right repair and get back on the road. Plus, you’ll save at least 10 percent on labor costs with your AAA membership.