I get several questions a week from readers with cars that won’t start. Some have an idea of what might be the problem—like a dead or weak battery—but most don’t have any idea where to start to pinpoint the root cause. But before I get into how to diagnose a no-start issue, I do have to ask some seemingly silly questions. I have seen many, many customers pay huge towing bills for these causes, so let’s just rule them out right away:
- Verify that your car is in Park. The car will only start in Neutral or Park.
- If you have an anti-theft device, make sure it isn’t malfunctioning.
- If the key won’t turn at all, your tires might in a bind against the curb, or the car may have rolled back a bit after you put it in Park. If this happens, try jerking the steering wheel to the right to release it, or you may need to physically rock the car to get the key to release.
If you don’t have any of these problems, you are unfortunately in a real no-start scenario. So here’s some basic information on how to troubleshoot your starter, alternator, and battery.
The three components required to get that engine started and keep it running are 1) a spark that ignites the fuel, 2) the fuel, and 3) compression—the process the engine uses to combine the spark and the fuel. So to diagnose your car, we have to systematically go through each of the processes your car uses for these components until we can find your problem.
First, let’s pay more attention to what happened and didn’t happen when you tried to start the car. Did you turn the key and absolutely nothing happened? Maybe a clicking noise or no noise at all? Did the engine try to turn over but just couldn’t make it happen? And maybe the radio and lights were still able to function, or maybe they didn’t have any power either.
If the lights are dim or completely dead, concentrate on the battery and its connections. If your headlights are functioning and still fairly bright, you can probably assume that your battery still has a lot of juice and is working properly. In this case, we now move to the starter.
Here’s what the starter does: When you turn the key, the battery feeds electricity to the starter, which starts turning over the engine. (The starter will only engage while the key is turned all the way on. As soon as you let off on the key, the starter disengages.) As the starter provides this movement within the engine, the pistons start pumping up and down inside a cylinder, which creates and releases compression within that cylinder. That compression causes a small explosion within the confined cylinder of the engine, and this reaction is what generates the engine’s horsepower.
So if the headlights are bright but nothing happens when you turn the key, you probably have a problem with the starter or the connection from the battery to the starter. Common problems in this area are a bad ground connection and either burned or damaged wiring.
When you turn the key and you hear the engine turning over, your starter is working. Of course, if you continue to try to start the car unsuccessfully, you can drain the battery in these attempts until the starter doesn’t have enough juice to even try any more, but that doesn’t mean that the starter isn’t working properly.
If the battery and the starter seem to be functioning properly, the next step is to check for fuel. Yes, customers really do have their cars towed in because they won’t start, and the only thing we have to do is to put gas in the empty tank. Verify that the car has fuel and the fuel gauge is working, then try to determine if you are getting fuel compression in the engine. Pay close attention to the engine sound—Is it turning all the way over? Is it turning over too slow or too fast? A broken timing chain or timing belt will cause the engine to turn over very easy and fast because the compression process is not happening.
When you turn the key to the On position and don’t hear a slight buzzing noise under the hood, there may not be power to your fuel pump or your fuel pump may not be working. And even if it is working, there may not be enough fuel pressure to start the car. If your mechanic suspects this is the problem, he can use a fuel pressure gauge to test this component. And yes, by this point, you are probably going to need to go to the mechanic.
More than likely, you’ve already noticed that as we go down this list, the diagnostics and probable problems are getting more complicated. Now we need to determine of the spark component is your problem, and this process can be even more tricky to test. You will need experience and the proper tools to work on spark issues, so this is also a job for your mechanic.
If you are at the stage that you need to call in expertise to fix your car, you have at least saved yourself and the mechanic time and effort ruling out the battery, starter, and empty fuel tank. Not only does he not have to guess what happened, but hopefully you have found the problem yourself.
If it’s time for professional intervention, call your mechanic and use what you have gained to relay specific no-start information. Saving him time to diagnostics can often save you money, and will always save both of you time and hassle.