7 Reasons Your Car Won’t Start But Lights Come On

You’re trying to get your car started, but the engine won’t turn over no matter how many times you hit the key. However, you notice that the lights on the dashboards and headlights are working just fine. So what’s going on? Why won’t your car start but the lights come on?

There are a few possible explanations for this, so in this article we’ve listed the most common, and to make it as easy as possible for you to narrow down the cause, we also dividend potential reasons for if the engine cranks or not.

Let’s dive into it!

The Engine Won’t Crank But Has Power

If the engine won’t crank it’s safe to say that there’s a problem related to electricity. This could be due to a number of things, such as a flat battery, a faulty starter, an ignition switch, or wiring issues. So let’s take a look at the most common of them.

1. Dead Battery

When you turn the key and nothing happens, the first thing we usually think about is the battery. So when the car won’t start but the lights come on, it’s only natural to wonder if there’s a problem with the battery.

But normally, you would think the lights would also go out when the battery is dead, right?Well, while that is the case most times, a dead battery can still have enough charge left to keep the lights on since these parts usually need no more than 20-30 amps.

But the battery won’t be able to provide enough power to turn the starter over, which instead often requires nearly 300 amps. But if that is the case, the lights would normally be dim.

But to make sure whether it’s the battery or not, the best way is to simply test it. There are a few different ways to test a car battery, but one of the simplest is to use a voltmeter or multimeter.

First, turn off the engine and open the hood. Then, locate the positive and negative terminals on the battery. Once you have found them, touch the red lead of the voltmeter to the positive terminal and the black lead to the negative terminal.

If the voltmeter reading is 12.6 volts or higher, the battery is fine. At 12.4 volts, you’ll still be able to start the car, but the battery is only about 75 percent charged. However, if it reads below 12.0 volts or lower, it’s a sign of a weak battery.

Now keep in mind that a dead battery could also be an indication of a problem with your car’s charging system, likely the alternator. So if your battery has a weak charge, you’ll want to charge it and see if your car starts before buying a new battery.

Learn more: Signs of a Bad Car Battery vs Alternator – Learn the Difference

2. Faulty Starter Relay/Solenoid

In order to start your vehicle, electricity passes through either a relay or solenoid that clicks over to the correct position when the ECM tells it to. If you don’t hear a clicking sound when you try start the vehicle, this might be why your car won’t start even tho lights still come on.

That is because these parts does not affect the battery or electrical accessories such as lights or radio. 

However, if you do hear a clicking noise, chances are your starter is fine but is not getting enough electricity. Probably because of a weak battery or bad alternator.

Related: How Much Is an Alternator? (With Repair & Replacement Cost)

3. Faulty Ignition Switch

The ignition switch is a part of the mechanism responsible for getting the engine going. So it makes sense that if your vehicle has a faulty ignition switch, you won’t be able to get your vehicle to start. And if this is the case, you won’t even notice your vehicle trying to start.

Like all electrical switches, the ignition switch can eventually wear out as it is one of the most frequently used switches on a vehicle.

And while you might be able to get the lights on as you turn the key to the third position, a faulty ignition switch might not close and complete the circuit as you turn the key all the way and, therefore, won’t tell the starter to crank the engine.

If you’re driving an automatic transmission car, it could also be that your vehicle doesn’t recognize that it’s in park or neutral. You can try the other gear to see if it helps with this problem.

4. Fuse And Wiring Issues

Before jumping into replacing the alternator, starter motor, or battery, it’s well worth checking the fuse box. If the ignition fuse or starter relay fuse is blown, a simple fuse replacement might do the trick when your car won’t start but has power.

Most vehicles have two fuse boxes; one is located in the engine compartment under the hood, while the other is usually found in the cabin, under the dashboard on the driver’s side.

If you have trouble finding it, consult your car owner’s manual.

However, it could also be a problem with the wiring, although this is less likely. If there’s a break in the wire going to the starter solenoid or ignition switch, it can cause problems.

Wiring issues are usually hard to troubleshoot even for the experienced DIY mechanic. So it may require the help of a professional if you suspect wiring issues.

Engine Cranks But Won’t Start

If the engine cranks but won’t start, the problem is likely not because of any of the mentioned above. This is because the engine requires a lot more than just electricity to start.

1. Bad Crankshaft Position Sensor

Most people know that the engine needs a spark to begin combustion, but many don’t know that spark timing is extremely important. Too late or too early and the engine will not fire at all or may misfire.

This is where the crankshaft position sensor (CPS) comes in. The CPS is responsible for telling the engine computer when to fire the spark plugs.

If the crankshaft sensor is faulty, it might cause the spark plugs to fire incorrectly. As a result, one of the most common symptoms is difficulty starting the vehicle, but it won’t affect the lights.

2. Bad Spark Plugs/Ignition coils

The ignition coil and spark plug are both parts of your vehicle’s ignition system, but they are not the same part. The ignition coil converts enough power from the car battery to create the spark, while the spark plug actually ignites the combustion needed to start the vehicle.

Now, if your car won’t start but lights come on, there’s a chance either of these two is faulty. Especially if you lately notice the engine misfires, loss of power, decreased fuel economy, or your car vibrates while idling.

But distinguishing between a faulty ignition coil and a spark plug can be difficult since a bad ignition coil can also lead to spark plug failure.

The easiest way to narrow down which part is at fault is to simply swap out the parts. And if you have some experience working on cars, you can often do the work yourself.

You can also hook up a multimeter directly to the ignition coil to test the resistance of the inner and outer coils and compare it to the value specified by the manufacturer.

3. Fuel System Issues

Another potential reason is that the fuel might not be getting to the engine. This can be due to a problem with the fuel pump, clogged fuel injectors or fuel filter.

Today, most fuel is perfectly clean and properly stored, so it’s more likely you suffer from a bad fuel pump than a faulty fuel injector or fuel filter. But over time, they can become clogged with rust or debris, and your car may not start up at all.

If you noticed the engine sputtering, stalling, or loss of power under stress before your car wouldn’t start anymore, there’s a good chance you have a problem with the fuel system.

And when it comes to the fuel pump, you should hear a quiet hum during its normal operation after turning the key to the third position. But if there’s an excessively loud noise from the fuel tank, it’s usually a sign of a faulty fuel pump.

Final Thoughts

Now that you know more about the common reasons why your car won’t start but lights come on, it’s time to take action.

If you don’t feel comfortable troubleshooting or repairing the problem yourself, it’s always best to take it to a professional.

But if you’re experienced with cars and are up for the challenge, troubleshooting and repairing the problem yourself can save you a lot of money. Just remember to take your time, be careful and always consult a professional if you’re unsure about something.


Why Won’t My Car Start But The Battery Is Fine?

If your battery is fine and the engine is cranking, you most likely have a problem with a bad crankshaft position sensor, fuel, or spark issues. But if your battery is fine and the engine doesn’t crank, it could be the starter, ignition switch, or fuse/wiring issues.

How Do You Tell If It Is Your Starter Or Your Battery?

The first thing you want to do to tell if it’s your starter or your battery is to listen for a clicking noise when turning the key. If you do, you likely have a drained or dead battery, and you can try jump-starting or charging your battery to get back on the road. If you can’t hear a clicking noise, the starter is probably at fault.

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Rickard Cefalk

Rickard is the owner of Caraspect.com and a dedicated and avid do-it-yourselfer who has always enjoyed working on his own vehicles since childhood. He now devotes his time to sharing his expert knowledge of car maintenance and other car-related information through his website.

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