Your car battery needs to be replaced every couple of years or so. Otherwise, your car won’t be able to start. With a new battery in place, you’d expect that your car will work fine just like new. But what if your car won’t start with new battery? What’s causing it? Well, the truth is your car is a piece of very complex machinery, and several things can go wrong and prevent it from starting. But don’t worry, we’ll guide you on how to diagnose your car. By the end of this post, you’ll be able to find the problem and how to fix it.
- How It All Works
- Bad Alternator Signs
- Troubleshooting – If It Doesn’t Crank
- Troubleshooting – If The Car Cranks
How Does The Car’s Battery And Alternator Work?
Before diagnosing why your car won’t start with a new battery, you should understand more about how the battery, the electrical system, and the starter in your car works. This will give you a better understanding of your car and make it easier for you to understand what might be wrong with your car. When starting a car, there are four critical components: the battery, the ignition switch, the starter motor, and the alternator.
Your car has a battery that powers your car’s electrical systems and starter motor. When you turn the ignition switch to start the car, the battery will turn on the starter motor. This is a small device consisting of gears that turns your car’s flywheel which cranks the engine. Once the engine is on, it will start running the alternator via the drive belt. The alternator then turns this mechanical energy into electrical energy. It then feeds this electricity into your car’s electrical accessories, as well as feeding it into the battery to prepare it for the next time you need it to start your car again.
Over time, the battery will lose its ability to hold electrical charges and will be unable to supply power to the starter motor, preventing you from starting the engine. This is what’s known as a flat battery. If the alternator isn’t working properly, it won’t be able to feed the battery with the necessary amount of electricity. This then leads to a flat battery much faster than it normally would. Here’s a video to learn more about batteries and alternators in greater detail:
Car Won’t Start with New Battery: Signs of a Bad Alternator
If your car won’t turn on with a new battery, it’s possible that the alternator wasn’t working properly. This means your new battery wasn’t being charged as it should and is thus losing charge. A new battery will last long only if the alternators are working well. In the case of a car that’s refusing to start even with a new battery, the most likely culprit is a bad alternator, here are the signs:
Dim or Unstable Headlight Brightness
As mentioned, the alternator powers most of your car’s electrical accessories when the engine is on. This includes the car’s headlights. A bad alternator won’t be able to supply the right amount of electricity to them, leading to weird behaviors. This includes a dim brightness to your headlights since they’re not getting enough electricity to power the lights.
Jumpstart your car with a second car to start it, and then turn on your headlights. Afterward, turn on other electrical accessories such as your car’s HVAC system and see if the headlights get dimmer. If it does, this means the alternator isn’t producing enough electricity and needs to be repaired or replaced.
Sometimes, a malfunctioning alternator will also produce too much electricity. In this case, your headlights will be overly bright. This is also a bad thing as too much electricity can damage your car’s battery and other components.
Slow or Malfunctioning Accessories
Since the alternators supply power to your electrical accessories, a bad alternator will affect your other accessories as well. For example, your power windows may take longer to roll up or down. Your car’s radio or entertainment system might also be slow to respond or might not even start at all.
Sometimes these accessories may be malfunctioning because of an isolated issue. However, if you have two or more electrical accessories in your car that isn’t working as it should simultaneously, it’s very likely the alternator is causing it.
Growling or Whining Noise
As mentioned, the alternator is powered by your engine via a drive belt. Over time, this belt can become loose. When it does, it will create a growling or whining noise when the car is running. If you hear this noise, this means the belt is slipping and the engine can’t power the alternator properly. Resulting in a less than the optimal output from your alternator.
The sound will usually come on when you turn on the AC. This is because your car’s HVAC system runs off the same belt system as the alternator. Turning on the HVAC puts more load on the belt resulting in noise. It might go away after a while, especially once your car warms up. But this means your drive belt is worn out and you should replace it. Sometimes your alternator should be fine in this scenario, and you only need to replace the belt.
Smell of Burning Wires or Rubber
If you smell burning rubber coming from your engine bay, the alternator’s drive belt may be wearing out. This belt is always under tension and experience a lot of friction, and since it sits close to the engine, it will wear out and can emit a burning rubber smell.
Meanwhile, a burning wire smell may come from an overworked alternator. The wires inside it can become frayed or damaged, and when the alternator is overworked, it will heat up greatly. This results in an unpleasant smell similar to an electrical fire.
The two scenarios above isn’t a common fire hazard, but it’s still dangerous and should be taken seriously. If you smell anything unpleasant in your car and it persists, we recommend that you stop driving and verify the cause. If the smell is coming from a fuel or oil leak in the engine bay, you should stop driving and have a mechanic take a look at the issue as this can result in a fire. Bottom line, don’t underestimate weird smells in your car. Unless you just bought a really cheap air freshener from a shoddy gas station.
Diagnosing a Car That Won’t Start with New Battery – Check the Battery, Alternator, and Fuses
If you see the symptoms above, you likely have an alternator issue. It wasn’t charging your battery, and now it’s flat and your car won’t start even with a new battery. What now? Well, let’s make sure that the alternator really is the problem. Servicing or replacing an alternator is quite expensive, so it’s best to make sure first before you spend a great deal of money. While we’re at it, you should also check the battery’s condition. If both the battery and alternator turn out to be fine, then we’ll guide you on how to check the ignition switch and fuses as well.
Keep in mind that this diagnostic guide is for a car that doesn’t crank when you turn the key. If the car still cranks, then your battery is still fine and there’s another issue – usually mechanical. If your car still cranks, we recommend skipping to the next section.
But before we start, does your car have an automatic gearbox? If it does, check if the transmission is in P or “Park”. You may have forgotten to move the gear knob into P the last time you drove, and now it’s preventing the car from turning on. This is a safety feature so the car doesn’t immediately roll off when you turn on the car. Simply turn the ignition on, make sure the transmission is in Park, and try again. If that doesn’t work, here’s how you diagnose a car that won’t crank:
Check and Test the Battery
First, you’ll want to visually inspect the battery terminals and their connectors. It’s new, so the terminals should be fine, but are the connectors clean? And are they tightly secured to the terminals? If not, this might be the problem. A rusty or loose battery connector may prevent the transfer of electricity. You’ll want to clean them, remember to turn off your car and then disconnecting the battery first. Afterward, use a battery cleaner and brush them with a bristled brush. Don’t forget to wipe and dry properly before you reconnect the battery.
Next, you should test the battery’s condition itself. You will need a multimeter for this:
- Set your multimeter to the 20 volts setting.
- Connect the multimeter’s red probe to the positive terminal and the black probe to the negative terminal.
- The multimeter will immediately take a reading. If it’s under 12.6 volts, then this verifies the battery is flat.
- If it reads 12.6 volts or more, then your battery is fine. In which case, you’ll want to check the fuses and ignition switch.
Testing the Alternator
Assuming your battery is flat, next you’ll want to check your car’s alternator to verify the problem. However, this requires you to jumpstart your car as you need the engine to be running to test the alternator. The only other way to test it will require you to remove the alternator and that’s far more complicated. Here’s how to test your alternator:
- Jumpstart your car with the help of another car. If you have a manual transmission, you can push-start your car with the help of a couple of helpful strangers.
- Once the car is on, connect the multimeter’s red probe to the positive terminal and the black probe to the negative terminal. Don’t forget to test set it to the 20 volts setting.
- The multimeter should read anywhere between 14.2 – 14.7 volts. If it reads somewhere around 13 volts, then the alternator is already weak and won’t be able to charge the batteries when you turn on accessories like the headlights and air-conditioning. In this case, try checking the cables running between the alternator and battery and see if there is any damage.
- If it’s far below 14.2 volts then you need a new alternator.
The average cost for a new alternator is around $500. For some cars, it can be as cheap as $200, but premium cars are likely to cost more. Here’s a video on how to check the alternator:
Check the Fuses and Ignition Switch
If both your battery and alternator seem to be fine and your car doesn’t crank, you’re likely looking at a fuse or ignition switch problem. To check the fuse, you will need to locate the fuse box. You can find this in your owner’s manual. Next, take out the fuses and see if there is any damage to the metal wires inside them. A damaged fuse won’t be able to send signals, preventing the car from starting. Most common fuses are no more than $20 to replace, but some specialized fuses may cost up to $100 to replace.
Meanwhile, the ignition switch is the electrical switch inside your car’s key housing. This one is a bit more tricky to diagnose, especially if you have a keyless system. But see if there are any irregularities when you try to turn the ignition on. If the car’s electrical accessories refuse to start even if the battery is fine, this could be a sign of a bad ignition switch. A car that suddenly shuts off or refusing to turn off could also be a sign of a faulty ignition switch. This is because the ignition switch is faulty and the switch isn’t moving properly. In this case, you’ll want to check the ignition switch and replace them.
Diagnosing a Car That Won’t Start with New Battery – If the Car Still Cranks
If a car won’t start with a new battery but you can still crank it, then the problem is likely to be mechanical. This means the battery, alternator, and other electrical functions are fine. But there’s something wrong with the engine that’s preventing the combustion process from starting, thus preventing the engine from turning on. Here’s how to troubleshoot it:
Check the Fuel Level, Pump, and Lines
First, make sure you still have fuel in your car. Some people might forget to fill up and now their car doesn’t have enough fuel to turn on. If you have enough fuel, the first couple of things you’ll want to check are the fuel pump and lines. If either of them is faulty, then your engine won’t get the fuel it needs. A fuel pump will last around 200,000 miles but may fail early if they’re not properly maintained or if you don’t use quality gas.
To check the fuel pump, turn on your car’s ignition or turn the key to the ‘ACC’ position. This will turn on all electrical accessories, including the fuel pump. If you hear a slight humming sound from the back of the car, then your fuel pump is working fine. But if there’s no sound, check the fuel pump fuse and voltage, as it may not be getting any electricity thus preventing the fuel pump from turning on. If the fuel pump turns out to be faulty, it will cost you around $400 to replace. However, this is just an average number and can cost up to $850 for some cars, not including labor.
If the fuel pump turns out to be fine, then next you’ll want to check for leaks along the fuel lines. The fuel line usually runs along underneath and in the middle of your car. See if there are any fuel leaks or any cracks in the lines, as this may cause fuel to leak out. Additionally, the fuel system needs pressure to run properly. The smallest leak could prevent fuel from getting into your engine.
Check the Fuel Pressure
If you can’t see any leaks along the fuel line, you’ll want to check the fuel pressure as the leak may not be visible. Low fuel pressure can also mean a weak fuel pump, dirty fuel filter, and clogged up fuel lines. To check the pressure, you will need a fuel pressure gauge and your car needs to have a Schrader valve. Here’s how to test the pressure:
- Connect your fuel pressure gauge to the Schrader valve.
- Turn your key to the “ON” position, this will turn on the fuel pump.
- Your fuel pressure gauge should read 40 – 45psi.
If it’s less than that, you will need to check the fuel pressure regulator and the fuel filter as well. We recommend taking a look at the fuel pump again as well, making sure that it’s working fine and there are no clogs in the fuel line.
Listen to the Fuel Injectors
If the fuel pressure is fine, next you’ll want to check the fuel injectors themselves. A bad fuel injector means your car can’t get fuel into the engine, preventing it from turning on. For this, you ideally need a mechanic’s stethoscope, but a screwdriver could the job as well.
What you need to do is get someone to help crank the engine whilst you listen to the injectors. Then touch the screwdriver against the fuel injector. You should be able to locate them by consulting the owner’s manual. Afterward, press your ear against the screwdriver, and have your friend turn the ignition key to crank the engine. If you hear a rhythmic clicking, then this means the injectors are working. Repeat this process for all the injectors, there’s usually one for each cylinder. If the injectors are working, this means your engine is getting fuel and there’s something else preventing it from turning on, so let’s move on…
Check the Spark Plugs
The combustion process that happens in your engine requires three things: fuel, air, and a spark. Now that we know fuel isn’t the issue, let’s check the spark. First, let’s check the spark plugs. Spark plugs are devices that create a spark inside your engine’s cylinder that combusts the fuel and air mixture inside. Not enough spark means the mixture won’t combust and the engine can’t run.
Remove the spark plugs and then visually inspect them. If they’re all black at the tip, then you probably need to replace them. But you can test them with a multimeter first before you decide to buy new ones:
If they’re bad, then you should change them and you should change the entire set. They should be around $10 each to replace, but you can get better ones for about $20 each.
Check the Ignition Coil
If the spark plugs are fine, then it’s possible your ignition coils aren’t supplying enough electricity to power the spark plugs. The ignition coil takes power from your car’s battery and converts it into high-voltage electricity for the spark plugs. A faulty ignition coil means the spark plug won’t be able to create a powerful spark even if they’re still in good condition.
The method to testing an ignition coil varies depending on the type of ignition coil you have in your car. We wrote a comprehensive guide already about ignition coils, and you should read it if you suspect you have an ignition coil problem. But most modern cars now have a coil-on-plug system, and this is how you test them:
- Remove the ignition coil you want to check and plug in the tester.
- Connect the ground wire to the engine.
- Start the engine and see if there’s a strong spark on the tester.
- Repeat the process on the other coils.
If the ignition coils are faulty, then you will need to replace them. The cost will vary depending on the type you have in your car. A can-type distributor coil is usually quite cheap, at around $50 to replace. But most cars now have a coil-on-plug system, which costs around $450 to replace the entire set.
Check the Air Filter, Intake, and MAF Sensor
The fuel and spark are fine, and the final thing your car needs is air. Open your air filter housing check if the filters are dirty. Also, check inside the air intake tube for any evidence that a small animal may have gotten in there. If the filters are clean, and there are no animal droppings inside the intake tube, then let’s move on to the Mass Air Flow (MAF) intake sensor.
The MAF sensor dictates how much air should be pumped into the engine’s cylinder. If it’s faulty, then it may be preventing your car from getting air. To test it, you will need a multimeter and find the MAF connector and unplug it. Here’s how to test them:
If the MAF sensor is faulty, then you will need to change it. They’re usually around $240 – $350 to replace.
Check Your Engine Compression and Timing
Finally, if your engine has fuel, air, and spark, that means there’s probably something wrong with either your engine’s compression or timing. A loss of compression inside the cylinders will prevent the engine from running. This can be caused by a blown head gasket or leak inside one of the cylinders, causing compression loss.
Additionally, your car has a timing belt. This timing belt controls the timing of the crankshaft and camshaft, making sure all the components are moving to the right position at the right time. If the timing is off, then your engine can’t run. These two can be quite difficult to test and diagnose, and we think it’s best if you see a visual guide on how to do this instead. Here’s an excellent video from ChrisFix on how to diagnose it, we recommend skipping to the 9:20-minute mark:
Car Won’t Start with New Battery: In Conclusion…
If your car won’t start even with a new battery in place, you should first check your transmission. If you drive an automatic, make sure that it’s in Park, and if you drive a manual, make sure it’s in neutral. After that, the troubleshooting process will depend on whether or not the car cranks. If it doesn’t crank, then check the battery, the alternator, and finally the fuses and ignition switch. If it turns out to be the alternator, then you will need to service or replace it. But don’t worry, you can still use your new battery afterward, although the lifespan might be shorter than it normally would be.
If the car still cranks, then that means the battery is fine and healthy. This means you’re probably looking at a mechanical issue that’s preventing your car from starting the combustion process and turning it on. Troubleshooting a car that won’t start is a lengthy process, so hopefully, our guide will help you to do it, and good luck!
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