That sinking feeling at the pit of your heart is only really applicable to a few dreadful and nightmarish scenarios. That sensation when your car won’t start but lights come on is precisely the situation that puts the fear of the automobile gods into your soul. We can all surmise that something terrible must be going on inside your car. Plus, we know that car repair can be gut-wrenchingly expensive.
But is it really so bad, or is there a simpler explanation as to why your car won’t start but lights come on? Indeed, the issue at hand could be caused by something as (relatively) innocent as a blown fuse. Or, it could entail serious problems looming, such as a faulty starter or ignition system. For now, the most important thing that you can do is to calm down, and don’t keep forcing the car to crank on.
Relax, and let’s try to assess the problem together. It all comes down to identifying that you have an issue with your beloved automobile. Then, we can diagnose it one-by-one, and see what’s the cause, or what might be a red herring. Once we’ve pinned down the source of this debacle, we can plan out a repair. So, here’s all you need to know about why your car won’t start but lights come on…
- Potential Causes (And Diagnosis)
- Key Turns, But Doesn’t Crank
- Engine Cranks, But Doesn’t Start
- Final Thoughts
What’s Causing Your Car Won’t Start But Lights Come On, And How To Diagnose Them?
Before we get started with discussing why your car won’t start but lights come on, here’s a tiny warning attached to this. As we mentioned before, if you’re having trouble starting up your car, stop forcibly cranking it. Repeatedly turning the key for extended periods in the hopes that it may eventually start could cause more harm than good. For starters (pun intended), there’ll be damage.
Your starter motor and its corresponding components could get damaged if you keep turning the key continuously for more than 15 seconds or so. Plus, doing this can wear out the battery’s charge, and the alternator as well as the ignition. If you find that your car won’t start but lights come on, just try to crank it on a few times. Never leave the key turned into its ignition state for long, too.
Should the lights, radio, and other electrical accessories turn on, but your car refuses to start, then do look at your options. What’s causing this to happen, and how can you solve this? To get a better understanding of this issue, we’ll divide this guide into two sub-sections based on your scenario:
- A – You turn the key successfully into the ignition or starting position, but the engine refuses to crank outright.
- B – Your engine does crank – ‘crank’ is defined as that “coughing” or sputtering as it tries to start – but the car can’t start properly.
On top of discussing the would-be causes as to why your car won’t start but lights come on, it’ll also be useful to guide you along diagnosing them. Such an explainer would be a brief step-by-step to narrow down your points of failure. In doing so, you’re better prepared to figure out how to repair it.
Situation A: Your Car Won’t Start But Lights Come On – The Key Turns, But It Won’t Crank
In this mock plot, you slot the key into the ignition. You then turn the key gently into the accessories (or ACC position). Here, you’ll find that everything appears normal. Your lights flash into existence, as does your radio, satnav, and other electrical components. But as you turn your keys into the ignition (or START, in most cars), your car doesn’t crank or try to start up.
Should you find yourself in this case of your car won’t start but lights come on, the likely culprit must be something electrical. You may be puzzled at this, understandably. If your lights could turn on, how can there be something wrong with the electrics? Well, know that while electricity might reach your radio or lights, but some circumstances prevent it from reaching the engine.
1. Dying Or Faulty Battery That’s Preventing The Car From Starting
You may have already ruled out the battery if your car won’t start but lights come on. After all, if the battery is dead or dying, why would your lights turn on, anyway? Aha, but you shouldn’t ignore your battery just yet! Know that turning on your lights, radio, satnav, or infotainment system doesn’t take a lot of charge. Your battery could be at death’s door, but that’s still sufficient to turn them on.
However, a dying battery with a reduced charge may lack the voltage and current for the starter and ignition. Compared to electronics, trying to ignite your car to life takes a significantly heavier toll on the battery. Suffice it to say, if your battery has a low charge and is close to dying, the starter’s load may be too great for the battery. Thus, your car won’t be able to start up. To diagnose this:
1.5. Diagnosing The Battery
- First, grab a multimeter or voltmeter to test the battery’s charge. If you’ve somehow got your car running again, you could stop by a local auto parts store. Some of them can offer a battery health check for free.
- With your vehicle turned completely off, remove the battery’s positive and negative terminal cover. Now, place your multimeter or voltmeter leads to contact both the positive and negative ends, respectively.
- Then, check the voltage reading. Your car battery should have a voltage of 12.6 volts or above. That said, it should be at least 12V to be nominal for starting up your car. For some context, electrical and electronic accessories like lights require between 20 to 30 amps to run. Starting a car, nonetheless, needs at least 300A.
- If the reading is lower than 12V, the battery needs a recharge. Should it be too low, say 9 or so volts, then it may not be sufficient for the engine to crank. Any reading lower than 12V with the car off is a red flag.
- Should this be happening to you frequently, you may want to inspect the battery connections. Those terminals can gather corrosion, which affects the rate of electrical flow. Alternatively, the connectors might be a tad loose. If the connections are rusted over, you can easily clean the terminals with a toothbrush and baking soda mix.
2. Starter Motor Is Faulty And Won’t Crank The Engine
The next potential component at fault ought to be the starter itself. Without the starter motor and its auxiliary parts, your engine can’t start. Depending on the severity of your starter’s wellbeing, your car won’t start but lights come on, at least. The easiest way to narrow the problem down to this as a problem caused by your starter is as simple as keeping your ears on alert. Hear out those “clicks”.
Turn the key into the ignition position, and listen for any noise. If you hear a distinct clicking sound, but your engine doesn’t start up, the starter may be the issue. It’s quite plausible that it’s not getting sufficient electricity to function. Or, it might be a bad relay or solenoid within the starter motor. But, if you turn the key and don’t hear any clicks, then your battery is completely dead.
2.5. Diagnosing The Starter
- First up, find the starter. It’s not immediately obvious where it’s located, but you can refer to your owner’s manual to find it. In most cars, the starter is often located underneath the exhaust or intake manifolds. The starter itself looks like a can or cylinder.
- You may have to get underneath your car to access the starter. While you’re there, inspect the wires and connectors between it and the battery. They could be the reason why your starter isn’t getting enough electricity.
- For some vehicles, unfortunately, you may have to remove and unbolt the starter to test it. If you’re not confident or lack the tools, ask a mechanic to drop by and see what’s wrong.
- With your owner’s manual in hand, discern the positive and negative terminals of the starter.
- Now, connect the multimeter’s or voltmeter’s positive lead to the positive terminal of the starter. It should be a barrel-shaped end closest to the actual starter motor. Subsequently, attach the leads to the negative end of the starter.
- Next up, have a friend try to start up the car. While they’re doing that, inspect the reading on the multimeter, and see if there’s a voltage drop. Any voltage drop shouldn’t exceed more than 0.5V under normal circumstances.
- Should the voltage drop more than 0.5V, there’s an issue with the starter. It may be a faulty starter solenoid or relay, or a bad connection with the battery.
- An alternative method is to pull out the starter signal fuse from the fuse box. The latter is usually located underneath your steering wheel. Examine the metal strip around the starter signal fuse. See if it’s damaged or burnt. If so, you’ll need to replace it.
3. Bad Ignition Switch That Won’t Start Your Car
Another component that’s vital to the start-up procedure of your vehicle is the ignition switch. This in particular can be diagnosed when your car won’t start but lights come on. If it refuses to crank at all when you turn the key, that ignition switch could be at fault. That’s instead of a wider problem inside the ignition system, such as the coils or connectors.
The ignition switch, to be clear, is that barrel that you slot your key into. In this circumstance, your ignition switch might be the cause if testing the battery and starter doesn’t turn up any clues. This ignition switch can prove a bit harder to diagnose compared to the battery. Once again, if you’re not comfortable – as with diagnosing the starter – have a technician drop by and inspect it.
3.5. Diagnosing The Ignition Switch
- First up, find your car’s ignition module, which is often found inside or near the distributor.
- Then, bring out your multimeter, and rotate your car keys to the OFF position.
- Now, attach or connect your multimeter’s positive lead to the back of the ignition module’s power supply wire. Next, attach the negative lead to the base of the distributor as a ground.
- Finally, inspect the voltage reading from that ignition module. If the reading is less than 90% of the battery’s voltage that you checked earlier, then there’s something amiss in the ignition system.
- Although, do bear in mind that there are multiple ways to check the ignition system. If you have the time and determination, test each one to see which particular part of the ignition might be at fault.
4. Damaged Or Burnt Fuses That Can’t Power Your Car
Another electrical problem where your car won’t start but lights come on involve the fuses. The fuses are a safety mechanism for your car. They ensure that if there’s a surcharge of electricity, a fuse will make certain that it can’t damage the rest of the electrics. In a way, seeing a burnt or blown fuse is a sign that it’s working to protect your car’s electrical system and electronics.
A continuation of your car not cranking when you turn the key, it may be attributed to one or a few blown or burnt-out fuses. The first thing you’ll have to do is to find the fuse box. As we mentioned earlier, most fuse boxes are located underneath the steering wheel. Nevertheless, some cars might hide it inside the glove box, or elsewhere. Consult your owner’s manual to see where it’s found.
4.5. Diagnosing The Fuses
- Diagnosing the fuses once you’ve found the fuse box is rather simple. The first step is making sure your car is turned off.
- Then, carefully pull each fuse out one by one, and inspect them. In particular, look at the metal wires inside the plastic housing of the fuses. And, examine the metal strips and connectors to see if there’s any sign of burning or damage.
- If one or more fuses are faulty, they may prevent electricity from heading to the starter relay. Thus, you won’t be able to start the car.
- Should you find a damaged or burnt fuse, you could swap it out with another fuse of a similar rating or higher. For example, you can remove the fuses for the headlights, and then use that to power the fuel pump.
- Although, most cars should come with a spare fuse or two in the emergency repair kit. Sometimes, these spares might be inside the fuse box itself. Therefore, replacing them shouldn’t be challenging.
5. Loose Ground Connection Preventing Your Car From Starting
Oftentimes, having a loose or poor ground connection can lead to your car being completely dead. In other words, without any power. Although, a loose ground connection may intermittently provide an open or close circuit randomly. Hence, certain functions – like the headlights and electronics – might still function. That’s even if the car is unable to crank or start up.
In this case, you can certainly experience that moment when your car won’t start but the lights come on. The ground connection on your car could be compromised due to corroded or damaged wires. It might also be caused (or accelerated) by poor fitment during a recent service or repair. Inspecting the ground connection is thankfully relatively easy.
5.5. Diagnosing The Ground Connection
- First and foremost, you’ll have to disable the entire ignition system. You may refer to your owner’s manual to do this.
- If your car has a distributor, you’ll have to disconnect the cables from the distributor cap. Then, use a jumper wire to ground that cable to the engine.
- Set your multimeter to DC, and select a voltage range that’s slightly higher than your battery’s voltage (12+ volts).
- Now, connect the multimeter’s positive lead (red) to a “clean spot” on the engine. This means an unpainted spot, where current can flow through.
- After that, connect the multimeter’s negative lead (black) to the battery’s negative terminal.
- Have a friend start up the car for you, and let it crank for 5 or so seconds.
- Inspect the reading on the multimeter. The voltage should be no more than 0.2V. Any higher, and it means there’s a loose ground connection creating unwanted resistance.
Situation B: Your Car Won’t Start But Lights Come On – The Car Cranks, But Won’t Start
In this scenario, we have a twist. As you rotate your key into the START position, your car is cranking. The lights turn on, and it seems as though the car is starting like normal. However, you soon realize that it keeps on cranking, without the engine turning on. If you’re able to sense that crank, it commonly denotes that your electrics are working just fine.
Nonetheless, there’s perhaps a more mechanical issue elsewhere on the car. This will be much harder to pinpoint, as it could be a wide variety of problems. It may be a bad transmission, low oil pressure, or a completely seized engine. With that in mind, however, the actual faults may be much simpler, as we’ll explore here.
1. Fuel Tank Is Empty And Failure In The Fuel Lines
This is perhaps the silliest excuse to your car won’t start but lights come on. You may have been neglecting to check your fuel level as of late. Without any fuel, your car will obviously fail to turn on, even if the electrics are working just fine. That’s why your lights could spark, but the engine refuses to turn over. In this case, the simplest diagnosis that you can do is to check the fuel gauge.
Unfortunately, your fuel gauge might be faulty, which is rare but it can still happen. Despite this, we could potentially have other points of failure within the fuel system as a whole. For instance, the fuel lines might be frozen shut, which can happen in sub-zero temperatures. When this happens, it can’t send fuel to the engine, and thus your car won’t start. The only solution is to let it slowly thaw.
2. Fuel Filter Is Clogged Up And Needs Replacing
The next culprit – once again related to fuel – are the fuel filters. These filters are crucial in any car, as they help to filter out unwanted debris or contaminants inside your fuel. Clean fuel enables your car to run smoother, with more potent combustion, and with fewer emissions. That said, and if your fuel filter hasn’t been changed in a while, it may be clogged up with debris.
The clogging is especially worse if you frequently run yours with a sparse amount of fuel. Depending on your particular vehicle, a fuel filter should be replaced after every 20,000 to 30,000 miles. Do take a peek at your owner’s manual, just to make sure. The fuel filter is usually located near the fuel tank and should be fairly easy to replace.
3. Damaged Fuel Pump Isn’t Sending Fuel To Your Engine
Another common fuel-based issue as your car won’t start but lights come on has to do with the fuel pump. Usually located in or around the fuel tank, this pump is what transfers the fuel across to the engine. By creating pressure, fuel flows from the tank to the fuel injectors and the combustion chamber. Should the fuel pump stop working, the engine won’t start.
A typical fuel pump is made to last a lifetime. In newer cars, the pumps have been moved to inside the fuel tank, as it allows the fuel to cool it. Still, on average, a fuel pump has a lifespan of around 100,000 miles or more. You can’t fix this yourself all too easily, unfortunately. Though, you may choose to diagnose the pump DIY-style to make sure that it’s the problem.
This can be done quite easily. As you turn the key into the ON position, the fuel pump should start to run. So, put your ears close to the fuel tank, and listen if you could hear a motor working. It ought to be a silent hum or whirr. If you hear nothing, then the fuel pump is a goner and needs replacing. A repair job like this should only really be done by a professional mechanic.
4. Faulty Spark Plugs That Can’t Start Up Your Car
Last but not least, we have the spark plugs. These are the components responsible for lighting up the compressed mixture of fuel and air, and subsequently starting up your car. Without spark plugs, your engine can’t combust. However, it would be a rather serious issue with the spark plugs to cause the entire car to not start up at all. It may correlate somehow with a faulty ignition or starter.
That’s because a car could still run even when one or more spark plugs have gone awry. If you have a V8, and two of the spark plugs are gone, it could still crank and run without a lot of issues. That said, you’ll experience what’s known as a misfire, or incomplete combustion. This is where, as per that V8 example, only six of the eight cylinders are igniting. This will cause its own set of problems.
For the car to fail to start completely, you’ll practically need all or most of the spark plugs knocked out. Alternatively, it might be due to a shorted-out or damaged spark plug wire. Diagnosing your spark plugs is relatively easy on newer cars. Although, you always have the option of calling up a local mechanic to come by and see what’s wrong.
4.5. Diagnosing The Spark Plugs
- Once you popped open the hood, getting to the spark plugs should be relatively easy. They’re readily visible, and if not, all you have to do is remove the engine cover.
- Now, you’ll have to disconnect the ignition coil and spark plug wires. This will require a 10mm socket wrench in most cars. Next, carefully remove the ignition coil, and set it aside.
- The easiest way to remove a spark plug is by using a dedicated spark plug socket. Remove each spark plug one by one, and examine them closely.
- A fouled spark plug is very noticeable, and shows numerous signs of wear. It may be covered in oil, soot, or carbon deposits that left a blackened residue on it. The spark plugs could also be melted, or the tips have been worn down. Cracks may also appear in the housing of a bad spark plug.
Car Won’t Start But Lights Come On – Final Thoughts
In all, that should summarise the most common causes on why your car won’t start but lights come on. Naturally, the actual cause could be endless, which may include a complete engine or gearbox failure, for example. Nonetheless, these are rather rare, as not being able to start your car can be narrowed down to electrical issues for the most part.
Otherwise, we could point fingers at there not being any fuel in the system. Remember, combustion requires three elements – air, fuel, and a spark. Lacking any one of those will result in your car failing to start. When it comes to fixing those issues, these potential causes that we’ve noted are relatively cheap compared to a seized engine. The priciest among them is replacing the fuel pump.
This could cost you anywhere from $250 to $1,000, accounting for parts and labor. A new starter is also decently expensive, ranging from $200 to $400. Meanwhile, a new ignition switch may set you back at no more than $200. In all, it’s not as terrifying of a repair as it might seem, no matter how the panic sets in the first time. Keep calm, and carry on diagnosing. It may be a simple fault after all.