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Miata Won’t Start – Troubleshooting Guide
So, your Miata won’t start. You climb inside, excited for a drive, turn the key, and nothing happens. What do I do? How much is this going to cost to fix? What’s wrong with this car?? This guide is designed to help you answer those questions, and save yourself time and money.
Before we get started, we are going to make a few assumptions and clarify a few things:
- This guide is to help you troubleshoot Miata no-crank-no-start problems. No-crank-no-start means that when you turn the key, you hear nothing, or only a “click”. If your car tries to start but doesn’t, you have a crank-no-start problem, which requires different troubleshooting steps and an entirely different guide.
- It’s assumed that you own a multimeter. If you don’t own a multimeter, buy one now. They are cheap, you need one to troubleshoot.
- This guide is written to help troubleshoot an NA Miata, but the logic and methodology apply to all generations of the MX-5 (or any other car.)
- It’s assumed that your car suddenly won’t start, and that nothing else has recently changed. For example, if you just had a new key made for your Miata and now the car isn’t starting – that is a very relevant recent change. Start by investigating what just changed before you follow this guide.
Start With the Battery
The #1 most common problem that will cause your car to not start is the battery, and it should be where you start troubleshooting.
- Start with the obvious – look at your battery posts and the connections going to them. If the battery connections are loose (meaning that you can wiggle them by hand), tighten them down and try to start the car again.
- If there is blue corrosion around the battery posts, then disconnect the battery and clean off that gunk using a terminal brush. Once you are done, reconnect the battery and try to start the car again.
- Assuming that the battery connections are nice and firm, and aren’t covered in crusty corrosion, you will need to test the battery. This is where you will need a multimeter. Turn on your multimeter and set it to DC Volts (20). Put the red lead on the positive battery terminal and the black lead on the negative battery terminal. See what the voltage of your battery is. A good battery will be putting out 12.6 volts.
- If you read that and went off to check if your battery is putting out 12 volts, stop. The number you are looking for is 12.6 volts, not 12. This matters.
If your battery is putting out less than 12.6 volts, you can’t trust it to reliably start the car.
At this point you can try jumping the car using jumper cables and another vehicle, a battery booster, or a trickle charger if you have the time to sit around and wait for the battery to charge up.
If your battery is more than ~3 years old, you might be better off just replacing it. In many cases, after a battery has been drained down, it will not reliably hold a charge again. While you might be able to jump it and get it running this one time, there’s a chance it could leave you stranded again in the near future.
Hopefully with a new or recharged battery installed, you are able to get your Miata running! If your battery was putting out 12.6 volts, and you’ve concluded this isn’t your problem, read on.
Let’s Alternate
Your sitting around, you’ve got a Miata that won’t start. EVERYONE, including friends and family, a tow truck driver, your coworker, or the guy working at the auto parts store are going to offer their opinion on what the problem might be.
At some point, someone is going to say “It could be your alternator.” When this happens, you can smile and nod, and promptly ignore their advice.
An alternator’s job is to charge your battery while the car is running. It is not involved in the process of starting the car. Therefore a bad alternator will not prevent your Miata from starting.
A bad alternator CAN fail at charging at your battery, and let the battery run low enough that your Miata won’t start. Let’s say this happens to you. You decide to listen to that family member / coworker / tow truck driver and go through the process of replacing your alternator. When you’re finished, guess what is going to happen?
Your Miata won’t start. You still have a dead battery. Which means you still need to start with the battery to continue troubleshooting.
And if you / your coworker / the guy at the auto parts store guessed wrong, and the alternator was working fine the whole time, you just spent ~$100 and a few hours of your time swapping out a part that wasn’t bad. That’s a bad feeling.
A bad alternator is easy to diagnose when your car is running. Get your car started before you worry about the alternator.
Starter Time
Assuming that your battery wasn’t the problem, and now that we’ve established a bad alternator won’t prevent your Miata from starting, the next most likely culprit is your starter.
There are a few ways to test your starter. While it is not a 100% conclusive test, one way that is very quick, easy, and generally accurate is to monitor battery voltage while trying to crank the engine over.
You will probably want a helper to assist you with this. Connect your multimeter to the battery once again. The voltage should be approximately 12.6. Have your helper attempt to start the car. The voltage reading should drop dramatically, likely down to about 10.5 volts. Starters require a lot of power to engage.
Assuming that the voltage does drop – it’s reasonable to assume that your starter is being energized. If you don’t hear any noises (beyond a “click”), at this point I would probably feel comfortable pulling the trigger on replacing the starter.
You could try and use and energize the starter directly using a battery or jump pack (although space can make this tricky.) You could also do a voltage drop test to see if there is high resistance on the starter circuit. Both of those are reasonable options, and some people may want to do them to get more certainty before buying a starter, but for me, the odds are high enough at this point that I would just buy a new starter.
If the voltage does not dramatically change while your helper is trying to start the car, you can reasonably conclude that your starter isn’t getting power – which is to say your problem is likely NOT the starter.
At this point you would probably want to bust out a wiring diagram and figure out where the break in the circuit is. From experience, I would probably go right to the main fuse / fusible link, and the main relay. If both of those were okay, then I would start tracing wires and looking for physical wiring breaks, as well as checking in to the ignition switch and neutral safety switch. These have been known to fail, but fortunately those failures are less common than routine batter / starter issues.
It’s never a good time when your Miata won’t start, and we hope this guide helps you resolve your problem and get back to driving! For more tips and tricks to keep your Miata running smoothly, follow us on social media.