DIY

Why Won’t My Car Start?

Reading Time: 4 minutes

It never fails—when your car refuses to start, it happens at the most inopportune time. It’s always when, say, you’re running late for a critical doctor’s appointment or a big work meeting. What makes things worse is that you usually have no idea why your car won’t start.

Is it the battery? Is it the fuel pump?

Unfortunately, the answer isn’t always straightforward. You might be surprised to find out how many issues can potentially prevent your car from starting.

Common Reasons Why Your Car Might Not Start

Automotive professionals break down no-start situations into two separate categories: crank-no-start and no-crank-no-start.

A no-crank-no-start condition is when the engine doesn’t turn over at all, or it sluggishly tries to turn over but cannot. On the other hand, a crank-no-start condition is when the engine turns over, like normal, but doesn’t fire up.

The two conditions have distinct lists of potential causes. Let’s take a look at both scenarios.

key is in the ignition but car wont start
A no-crank-no-start condition is when the engine doesn’t turn over at all, or it sluggishly tries to turn over but cannot.

Engine Cranks Normally (or Faster Than Normal) but Doesn’t Start

When you turn the key to start your car, the battery supplies power to turn the starter motor and crank the engine. Then, fuel and air enter the engine, where they’re compressed and ignited to create a series of small explosions. It’s these explosions that send the pistons downward in the cylinders to get (and keep) the engine running.

Without an air/fuel mixture, spark, and compression, the engine will crank normally (because the starting system is working properly), but it won’t start and run.

A crank-no-start condition such as this is typically caused by a problem with fuel delivery, spark delivery, or engine compression.

Fuel Delivery Issues

Obviously, your car needs fuel to run. If the engine isn’t getting enough fuel, there’s a good chance it will crank but not start. Fuel pressure and/or volume problems can stem from a number of sources, including:

Loss of Compression

Before the air/fuel mixture is ignited inside the engine, it must be compressed by the piston moving upward in the cylinder. A significant loss of compression on multiple cylinders can prevent the engine from starting.

Common issues that could cause a loss of compression and, therefore, a crank-no-start condition, include:

Ignition System Issues

Your car’s ignition system creates the spark that ignites the air/fuel mixture inside the engine. Ignition system problems that prevent multiple cylinders from receiving spark can easily lead to a crank-no-start condition.

Examples include:

Engine Doesn’t Crank and Doesn’t Start

As was mentioned, the starter motor cranks your engine over to get it going. But the starter motor is just one part of the starting system. Other parts of the system include the battery, ignition switch, neutral/park safety switch (or clutch start switch if the car has a manual transmission), and accompanying circuitry.

Note: Many late-model cars rely on a push-button, control module, and smart key fob rather than a traditional ignition key and switch.

A problem anywhere in the starting system can result in a no-crank-no-start condition. Here are some of the most common causes:

It’s worth noting that, in some instances, the engine may try to turn over sluggishly but not be able to get the job done. For example, a weak battery might have enough juice to turn the engine over slowly a couple of times, but it won’t be able to turn the engine fast enough to get the car started.

What to Do When Your Car Doesn’t Start

As you can tell, there are a LOT of potential reasons why your car might not start. Some issues, such as a dead battery, are easily recognizable to most drivers—but other causes are far more difficult to pinpoint and require extensive knowledge to diagnose.

If you’ve got the know-how and tools, you might try to troubleshoot a no-start condition yourself. Otherwise, it’s best to let a professional fix the problem—and fix it right.

That way, the next time you’re rushing to a big meeting, you’ll have a better chance of not getting stranded beforehand.

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Author

Mia Bevacqua

Chief Mechanic at CarParts.com

Mia Bevacqua is an automotive expert with over 15 years of industry experience. She holds ASE Master, L1, L2, and L3 Advanced Level Specialist certification, as well as a bachelor's degree in Advanced Automotive Systems.

Throughout her career, Mia has applied her skills toward automotive failure analysis inspections, consulting, diagnostic software development, and of course, freelance writing. Today, she writes for companies around the world, with many well-known clients showcasing her work.

Mia has a passion for math, science, and technology that motivates her to stay on top of the latest industry trends, such as electric vehicles and autonomous systems. At the same time, she has a weakness for fixer-upper oddballs, such as her 1987 Chevy Cavalier Z-24 and 1998 Chevy Astro Van AWD.

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