Few things are more frustrating than getting into your car in the morning, turning the key in the ignition or pressing the start button, and hearing the car struggle towards no end. You can hear something happening, but the engine simply doesn't engage in your car won't start. Most people refer to that as the car cranking but not being able to start. There are a number of reasons that this can happen, and all of them are pretty frustrating and demand immediate attention if you want to get your car up and running again.
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What Causes a Car to Crank but Not Start?
The first thing to understand is that when you have a crank but no start that doesn’t means your starter is the only source of the problem. That sounds a little ironic considering the problem is the car doesn't start, but the starter may still be working fine, and there's a problem somewhere else.
With that in mind, there are a number of places that you can check right off the bat if you're noticing that your car is cranking but not starting properly. As with many problems in cars, there are fortunately a number of potential reasons for this to happen, so you may have to eliminate several before you click on the one that is the actual culprit in this case.
Fuel Problems
It stands to reason that if you have a problem with the fuel in your vehicle, it's not going to be easy to get it started. This could be something as simple as your gas tank is completely empty and you're just trying to get it started with some fumes. Obviously, that's not going to work, so you'll hear the engine struggling but not actually turning over.
The issue with fuel can get a little deeper than simply not having fuel, however. Issues with the flow of your fuel are also directly responsible for a car being able to crank but not start. This could in turn have a number of additional issues that have caused it to transpire. For instance, this could be as simple as a fuse for the fuel pump that has gone off or burned out. If the fuel pump is unable to work the way it's supposed to, obviously you're not going to be getting fuel injected into the combustion chamber of your engine so that the combustion reaction can occur and start the car for you.
Another issue is that it could be the fuel pump itself is just broken. Like the issue with the fuse not functioning, when the fuel pump is unable to work obviously, you're not getting the correct amount of fuel.
Additionally you could have a fuel injector that has gotten clogged with some sort of debris, or it's just misaligned or broken. There's even the possibility that something has happened to the fuel in your tank. You could have accidentally used the wrong kind of fuel in your vehicle which will prevent it from starting properly. That's why you can't put diesel fuel in a normal engine and vice versa. Additionally, if your fuel has been contaminated in some way with any kind of foreign substance it could potentially cause the same reaction.
Battery
If you find the engine cranking slowly it's possible that your battery has died or is on the verge of dying. Additionally, the battery may be still mostly functional but you could have a problem with terminals being corroded or coming loose, or even the starting wires malfunctioning. You can check the voltage of your battery using a multimeter while you're trying to crank the engine to see if this is the case. You should be reading 10 volts if your battery is working properly.
Starter Motor
As we said earlier the starter motor isn't necessarily the problem when you have a crank but no start, but it could be a contributing factor. A weak starter motor that is using too many amps to crank the engine will not be able to also get the ignition system in the fuel injectors working. That will cause the starter to make sounds when you try to crank the engine to indicate it's probably the source of the problem.
Fuses
You can check the fuses in your car once you've turned it off. Check the wiring and remove each fuse to do a visual inspection. You can use a test light to check each fuse for current flow. If everything is damaged, you can pick up replacement fuses fairly cheaply at any local auto supply store. Even Walmart will have them in the auto department.
Spark Plugs
If you don't have spark in your engine, then it's not going to turn over. Lack of spark can be caused by a number of problems from something as obvious as damaged spark plugs to a problem with your ignition module. It could also be caused by a faulty crank position sensor or something wrong in your ignition to circuit.
If your spark isn't happening at the exact right time, then the air and fuel mixture won't ignite at the right time, and your engine simply can't get started as a result.
Some of these issues are harder to diagnose than others but you could do a visual inspection of the spark plugs to determine if there's anything wrong with them and specific. If you notice a lot of build-up around the gap, particularly a black carbon residue, that could definitely be causing the problem.
Cold Injector
This one doesn’t affect every vehicle, but some vehicles use what is called a cold start injector. It only works when the engine is cold which is different from how a regular injector works. If the switch that monitors the temperature or part of the control module fails, the wrong signals may be getting transmitted and the engine will not start properly as a result.
Low Compression
The cylinders in your engine have to have precise compression ratios in order to work properly. If any of the cylinders in your engine have low pressure, air from the combustion reaction will leak past the piston rings and that lowers the overall functionality of that cylinder. That means it's not able to turn the crankshaft properly, and your engine will not be powered properly.
Compression issues can be caused by problems with your timing belt or a damaged camshaft. If your engine is overheated, that can also lead to this problem. You can either take your car to a mechanic to get this checked or you can use something called a compression gauge tester. Most drivers don't have these kinds of tools on their own, so you consider yourself some time by going to a mechanic to get that test done for you.
Security System
Most people don't consider this but modern security systems in most cars have an engine immobilizer as part of their anti-theft system. If there is an error somewhere in the software or some other kind of malfunction with your security system, your car may be disabling your engine because it thinks someone is trying to steal it. If that happens, you'll need to run a diagnostic to determine the source of the problem.
Canister Vent Valve
Your car has something called an evaporative emission control system, also known as EVAP. The canister vent valve is part of this system and it stores harmful fuel vapors to prevent them from being released into the atmosphere. The vapors are then redirected into the intake manifold where they can be burned. When this valve fails it's possible for it to cause the engine to not start properly.
EGR System
EGR stands for the exhaust gas recirculation valve which recirculates exhaust gases to the intake manifold so that they can be burned in your engine again. This has a two-fold purpose of lowering the temperature of your engine and also helping to reduce harmful emissions. If the valve gets clogged, or stuck in the open position, it's not able to do its job properly and it's possible that your engine will not start properly as a result. There will probably be a lead up to this problem, however. You might have a length of time when your engine stalls frequently or you're giving some serious problem with rough idling that can help indicate that this is the problem you should be looking at.
Sensors
There are a couple of sensors that can go wrong in ways that will prevent your engine from starting even though you're getting a crank. For instance, the mass airflow sensor, known as the MAF sensor, monitors the density of air entering your engine. If the sensor gets blocked by dirt and debris, it's not able to work properly any longer. Also, the sensor can simply die after extended use from general wear and tear. When that happens, your engine may also not start the way you expected you.
The engine coolant temperature sensor, or ECT sensor, lets your car's computer know the amount of fuel that the engine needs and also when your engine has reached optimal temperature. When the sensor fails it can affect transmission and cooling as well as ignition timing. All of these could potentially lead to problems with your engine not cranking properly.
You have a TPS sensor in your vehicle as well, which stands for throttle position sensor. As the name suggests, it monitors the position of the throttle valve and sends signals to the computer to regulate the air-fuel mixture. If this sensor fails it may prevent your engine from starting properly.
The MAP sensor, or the manifold absolute pressure sensor, measures the barometric pressure and compares it to the pressure in the intake manifold vacuum. Like the MAF sensor, if this one gets gummed up somehow or fails, it can stop your engine from working properly. Not every car has one of these answers, but you can check out your owner's manual and see if yours does and how to deal with the problem.
Vacuum Leak
There are a number of places throughout your engine where vacuum leaks can occur, and when they do, they can definitely lead to the engine not being able to start properly. These can occur anywhere from the EGR valve to the intake manifold gasket to the power booster vacuum hose and beyond. Because there are so many locations where a vacuum leak can occur, it can be difficult to narrow down the precise location without the help of a mechanic.
Carburetor
Modern vehicles don't actually have carburetors anymore as they've been effectively replaced by Fuel Injection systems. That said, if you have an older vehicle then it's likely you still have a carburetor in it. The carburetor could definitely be responsible for your car being able to crank but not start. Problems such as the carburetor being flooded can lead to this happening.
The Bottom Line
When your car will crank but not start it's difficult to know exactly where you should start looking to figure out what the problem is. As we have seen, there are numerous different issues in many systems in your vehicle that can cause this. We've detailed 13 different ones on this list but there are some other problems that could still potentially pop up. These are just the most common ones that tend to cover the majority of cases of a car cranking but not starting.
If you noticed a problem in any of these areas and your car is not starting, that can help you narrow down exactly where it is you need to look in order to get the problem fixed. Obviously, your car is no good to you if you can't get it started, so this is the kind of thing you want to get taken care of as soon as possible. With the knowledge of exactly where the problem could be stemming from, you can save yourself a little bit of time and potentially even get some of these issues fixed on your own as doing things like replacing fuses and spark plugs, or checking the power output from your battery is something that many of us can do on our own without having to go to a mechanic.