4 Reasons Why Your Car Starts But Won’t Start
Your car engine starts, but won’t start. You turn the key over and over, and all you hear is the dreaded “click, click, click.” What could be preventing your engine from starting? Learn about the most common reasons why your engine will start but won’t start so you can identify the cause and get your car back on the road.
Cranking and Starting
When you turn the key in the ignition, the starter motor turns the flywheel, which spins the engine’s crankshaft. This is the cranking process (also known as cranking). The engine is turning, but not yet started. All you need to do is crank it to start the engine.
Starting the Engine
Starting is when the engine actually ignites and begins to run under its own power.
Why does my car start but not start?
As mentioned above, turning the key in the ignition or pressing the “push to start” button activates the starter motor, which spins the flywheel and ultimately the crankshaft. This process can be interrupted if there is a problem with the system and your car’s engine does not continue to run after “starting” or cranking.
For an engine to start properly, it needs sufficient fuel pressure, properly timed ignition, and good compression. If it won’t start, the problem is usually caused by one of these systems, but it could also be the starter system. Here are the most common reasons this happens:
1) Spark problems
Loss of spark can be caused by a damaged ignition module, a faulty crankshaft position sensor, a flooded engine (occasionally happens on older or high mileage vehicles), a faulty spark plug, or a problem with the ignition circuit. Examples: wiring, a security system (fuel flow may be turned off to prevent theft or the chip in the key may be defective), or a faulty ignition switch.
If there is a problem with the ignition timing system, misaligned ignition timing can occur. This can be difficult to diagnose, but an ignition timing light is a useful tool to make sure all cylinders are firing accurately on schedule.
To determine if you have a spark problem, visually inspect the distributor and its cap (if your vehicle is equipped), as well as the spark plug wires. These can wear out over time. You should use a spark tester to verify that a proper arc is coming from each ignition wire or ignition coil.
If after multiple starting attempts the engine seems flooded, remove and dry the spark plugs. Then reinsert and try again.
2) Insufficient Fuel Flow
Fuel pressure and flow problems can be caused by a damaged fuel pump fuse, a faulty fuel pump, contaminated or improper fuel in the tank, a broken or clogged fuel filter or injector, or simply an empty fuel tank (your fuel gauge may not always read accurately).
Proper fuel pressure is important for starting or running a car engine, especially a fuel-injected engine. With the ignition in the “on” position, listen for the fuel pump to whir for a few seconds. If you don’t hear a humming sound inside the car or behind the fuel tank, the pump may be faulty and not delivering fuel to the engine at all.
Note that some fuel pumps only pump while the car is starting, so some cars may not make an audible noise. You can find more information about your specific model online or in your owner’s manual.
If you can hear the fuel pump, try holding a flat-head screwdriver (with the handle next to your ear) against each injector while the car is starting. You should hear a quiet clicking sound coming from each injector as it fires, transmitted through the shaft of the screwdriver.
Some cars are equipped with a safety feature called an inertia switch that automatically shuts off fuel flow after a collision. If your vehicle has recently been crashed, consult your owner’s manual to see if your vehicle has this feature and how to manually turn it on to restore fuel flow.
3) Low Compression
All cylinders require compression for an engine to function properly. The compression ratio compares the maximum and minimum cylinder volumes during each stroke of the piston. If one or more cylinders have low compression, air escapes from the combustion cycle through the piston rings, limiting the work that the cylinders can do to turn the crankshaft. Compression problems can be caused by a broken or loose timing belt or chain, or a cracked overhead camshaft. Engine overheating is also a major issue that can prevent your car from starting.
Use a compression gauge or tester to determine if your car has a compression problem. In this case, a leak test will be done as a secondary test to look for leaks in the cylinders. If you are not confident doing it yourself, a professional mechanic can perform these tests and inspect the cylinders.
4) Power Issues
Another possible issue is a weak starter motor that draws a lot of amps to crank the engine and doesn’t have enough power left to turn on the injectors and ignition system. In this case, you’ll notice the starter motor making strange noises when you try to crank the engine, or it might not start at all.
Weak or corroded battery cables or a dying battery can contribute to the problem as well. Check the voltage of the battery with a multimeter while cranking the engine. It should show over 10 volts.
Check for blown fuses by visually removing and inspecting the wiring of each fuse when the car is shut off. If they appear to be in good condition, put them back in then try turning the car ignition into the “on” position and using a test light to check each fuse for electrical current flow. Replace any damaged fuses with new ones from an auto supply store.