When your engine cranks but doesn't start it can indicate a number of problems with your vehicle, but none of them are the kind of things you want to experience. What this means is that when you turn the key or press the button to start the car the starter engages and attempts to get the engine going, the flywheel begins to turn and rotate the crankshaft but then it simply can't continue this process to actually get your car started. Something has prevented the full engine start from occurring. It's one of the most frustrating things that you can endure as a driver, getting into your car and trying to turn the key in the ignition only to hear the vehicle struggle but not actually get started.
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Because there are a number of causes for this to happen there are some signs and symptoms that you can be on the lookout for that can let you know the potential cars for the problem which will also help you figure out the best way to get the problem fixed. Let's go over some of the most common reasons why your car cranks but won't start.
Spark Problems
The most obvious reasons for a car to crank but not start is a problem with the spark that is meant to ignite the fuel and air mixture for the combustion reaction. There are a number of causes for a spark to fail in your vehicle from a flooded engine, bad spark plugs, a faulty crank position sensor, and of course a bad ignition module. The wiring of the ignition system could also be problematic which would lead to this.
One of the easiest ones to test would be a problem with the spark plugs which only have a limited lifespan and do fail after about 30,000 miles to 100,000 miles depending on the type of spark plugs that you have. Cheaper spark plugs are going to fail a lot earlier, and the more expensive platinum or iridium spark plugs will last longer.
A visual inspection of your spark plugs and the spark plug wires can give you some idea of whether or not they are badly corroded or covered in carbon build-up, and you can use a spark tester to determine if the spark plugs are properly functioning. Replacement spark plugs are actually really cheap, and they only cost you somewhere between $10 and $20 depending on the type of spark plugs you’re using.
Bad Ignition Switch
The ignition switch is what activates your car’s electrical systems when you try to start your vehicle. When your ignition switch isn't working properly the steering wheel will remain locked, the spark won't fire to get the combustion reaction going and none of the electrical components in your vehicle will work.
The switch connects to the ignition coil, the starter solenoid, and your starter motor. This is what you either press to get your car started or insert the key into turn to get the car going. When it fails, your car will be unable to start at all. If you need a new ignition switch you can buy just the part for between about $35 and $250, and you can get it replaced by a mechanic for around $150 to $500.
Security System Problems
Most modern security systems have an engine immobilizer included as part of the anti-theft system that they employ. These come into play if someone tries to start the vehicle but doesn't have the correct key so that the car will shut the engine off to prevent it from being started. However, if your security system has a problem, like a fuse is broken or shorted out, there is a software error, or the chip in your key has an issue then the security system may not recognize you as the actual driver of the vehicle. When that happens, it can lock up your engine on you and prevent it from turning over when you try to start your car.
Bad Fuel Flow
A problem with your fuel pump or a fuse for the fuel pump could lead to issues with fuel not being able to get to your injectors to start the combustion reaction. It's also possible that a bad fuel filter or fuel injector could cause this problem as well. Of course, one of the most obvious problems here is just that you don't have any fuel, something that can be overlooked from time to time because we tend not to think of that as the cause of the problem and it's pretty embarrassing when it is the issue.
Problems with your fuel line could also lead to this, especially in the winter. Fuel lines are subject to freezing up on occasion in cold weather. If that's the case, due to moisture being present in the lines, then it simply can't flow to your engine and it will not be able to start. The only solution to this particular problem is to find a way to thaw the fuel lines out again. Your best bet is to keep your car parked indoors if at all possible during the extremely cold weather, although that's not always a possibility.
When you don't have the right fuel pressure in your vehicle it's difficult for the engine to actually turn over. You might hear some buzzing from the fuel injector, but if you don't hear that then it's also possible the fuel pump has completely died and is no longer able to pump fuel from the tank to the engine. In some rare circumstances this could be caused by a problem with an inertia switch that has shut off your fuel pump after an accident. If you haven't had an accident recently, this could still go off if it's been damaged in some other way.
If your fuel pump is failing and you need a replacement, you're looking at a cost anywhere from $700 to as much as $2,000 to get it fixed. If the inertia switch has failed and needs to be replaced it can cost from $150 to $200. And finally, if it's the fuel injectors themselves that failed on you, a repair cost could be between $800 and $1,500 to get them replaced.
Blown Fuses
Sometimes it's a simple matter of a fuse no longer working that can prevent your car from starting when you put the key in the ignition. If any circuit is not able to be completed from the starter system, your car's computer or the fuel injectors then those systems won't function properly, and your car will not be able to start. You can check in your owner's manual or online to find out where the fuses are located in your car and give them a visual inspection to see if they are working properly any longer or not. If you need to replace them, car fuses are actually pretty cheap and can be picked up at most auto shops.
Sensor Malfunctions
If you're having problems with things like your mass airflow sensor, which monitors the density of air that enters your engine, it can prevent your car from starting properly. These sensors can get blocked by dirt and debris so they're unable to send the proper signals to your car's computer. Other sensors such as the engine coolant temperature sensor alerts your car's computer to when your car has reached optimal temperature. When it fails it can affect the ignition timing and cooling systems. It could also potentially cause a problem with your ability to get your car started properly. Your TPS sensor, the throttle position sensor, also helps regulate the air and fuel mixture. When that fails then you may not get the correct mix which prevents the combustion reaction. And finally your MAP sensor, the manifold absolute pressure sensor, can also cause the air and fuel mixture to go off preventing combustion from occurring.
Poor Compression
The compression ratio in your engine compares maximum cylinder volume to the minimum cylinder volume during each stroke of the pistons. If you have low compression, air leaks past the piston rings which in turn reduces the amount of work that they can do to spin the crankshaft. Compression problems that reduce the overall function of your engine are usually caused by bad timing belts or a problem with the camshaft. An overheated engine can potentially also cause this problem.
When it comes to a compression issue, if it's bad enough it can stop your engine from starting in the first place. You can use something like a compression gauge tester to see if there is an issue with the compression in the vehicle. If there is such a problem present, then you need to do a check for leaks in your cylinders to find out which one it's happening in and why. It's possible to do this job yourself, but most people would prefer to take it to a mechanic to get it done since it's sort of complicated.
Canister Vent Valve
A canister vent valve in your car is part of the EVAP, or evaporative emission control system. It stores fuel vapors and prevents them from being released into the atmosphere by redirecting them into the intake manifold where they can be burned again. If the valve fails it can limit the proper flow of gases through your exhaust preventing your car from even being able to start.
Bad Starter Motor
Although the starter is often the first thing people think of when a car engine cranks but won’t start, it’s not always the case. Still, if your starter is drawing high amps but then is unable to get the fuel injectors started it will make some clicking sounds as it struggles to start but then nothing will happen. If you need to replace your starter motor it may end up costing you upwards of $400 to $600.
Dying Battery
A car battery will only last you about 3 years to 5 years at maximum. The ideal charge when you check your battery with a multimeter would be 12.6 volts. If you're pulling 12.3 volts or lower than you definitely have a problem with a dying battery. If it goes below 12 your battery is essentially dead and useless for powering an automobile.
Your battery can also be drained for other reasons beyond simply old age. Components plugged into your car that draw power can put strain on your battery, and of course if you leave something like your lights on overnight by accident then that's also going to pull power from your battery as well.
If your battery cables are weak or corroded then they may also be unable to transmit the correct power from the battery to the rest of the vehicle which will stop the starter from working properly. Replacing a car battery should cost around $100 to $200 if you take it to a mechanic to get the job done, but you can save money by doing it yourself. New car batteries may only cost around $50 or so.
The Bottom Line
As you can see there are a whole host of reasons why your car may be able to crank but not actually get started. Unfortunately, with such a wide range of issues, it can be hard to properly diagnose what's going on in the first place. Something as simple as a spark plug could be fixed for just a few dollars, but a bad starter motor or a faulty fuel pump could end up costing you quite a bit more if that's the cause of the issue.
The best way to get a diagnosis for sure if you take is to a professional and have them figure out what's going on so that you can get back to driving and not have to worry about this any longer. If you find your card is unable to start, call a tow truck and take it to a licensed mechanic so they can diagnose the problem and get you back on the road as soon as possible.