Why Car Won’t Start in the Cold?


Cold weather can cause many issues for vehicles and it can be frustrating to deal with a car struggling to start in the cold. Fortunately, most cold-weather vehicle problems can be easily fixed. 

There are multiple reasons why a car won’t start in the cold. A common problem is a battery but it could also be a problem with your fuel, oil, engine coolant sensor, a faulty idle air control valve, a carburetor issue, a vacuum issue, or an EGR leak. 

This article will go over all those issues to help you determine what is causing the problem and fix it. 

Battery Problem

Batteries just don’t work as well when they are cold. This is particularly true of an old battery. It takes extra effort to get an older battery to start and adding a cold temperature just makes it harder. 

You can jump off your battery and that will work for a short-term solution. Let it run and warm up about 20 minutes after the jump so the battery can recharge itself. 

While this will work to get your car started, you don’t want to be forced to jump it off every time the engine gets cold. There are some things you can do to avoid the problem. 

First, you can keep your car garaged or covered to keep it from the extreme cold. That will help reduce the struggle the battery has to start. However, this is only part of the solution. 

You should also tighten your battery cables and check for corrosion on the terminals as that can be impacted by weather.

You will need to get your battery tested to see how much life is left in it and get a new one if necessary. Many retail auto stores will test and recharge a battery for free and recharging it fully will buy you some time. A recharge will take 24 hours so you will be without a vehicle during the process. 

If your battery is more than two or three years old, it’s best to go ahead and replace it. That way you can ensure your car will start in cold weather. 

Read: How Long Can a Car Battery Sit Unused?

Fuel Issues

A fuel issue during cold weather can occur either with the fuel itself or with the fuel delivery system. Gas will be the most common issue. 

Those with low fuel levels will experience more problems in the cold than those who keep their gas tanks full. Gasoline needs to vaporize for a car to work and lower temperatures make it harder for fire to create vaporization. 

The less gas you have, the harder that will become because it needs to pump more into the fuel lines and engine to start on a cold day. 

The other problem is cold weather will cause condensation within the fuel tank, especially if it’s low on fuel. Water weighs more than gas so it will drop to the bottom of the tank. Then, it freezes with cold-weather preventing fuel from getting through the fuel lines. 

Diesel gas has its own set of issues with cold weather because lower temperatures can turn it into a gel, making it hard to pass through fuel lines. 

The other part of fuel problems is how cold affects the fuel delivery system. Cold weather can cause an already failing fuel pump to bite the dust completely and can also do a number on clogged fuel injectors. 

A failing fuel pump or clogged injectors may not show symptoms on a warm day but cold temperatures can cause what is in the pump or the clogs to freeze. That prevents fuel from going where it is supposed to go and prevents your vehicle from cranking. 

It may take a mechanic to check for injector clogs or to check the fuel pump.

Read: How to Start a Car With a Bad Fuel Pump

Oil Issues

The oil keeps your car engine lubricated and it’s the lifeblood of the car. Many people don’t realize there is an oil you can use for summer and oil for winter. If you haven’t had an oil change since it turned cold, your problem could be the oil being too thick to run.

Oil gets thicker as it ages so it may be too thick anyway if you are due for an oil change. It’s important to get your oil changed regularly and that becomes more important during the winter.

Engine Coolant Problems

One of the first and easiest things to check when your car is having trouble starting in cold weather is your coolant. You need a mix of water and coolant to keep your engine from freezing in cold weather. 

A car that is low on coolant will have problems starting. Beyond that, you may also want to have a mechanic check your coolant sensor. A bad sensor means your vehicle isn’t using the coolant mixture properly. 

Your car will likely produce a check engine light if the coolant sensor goes bad. Be sure to take your vehicle to a mechanic if the check engine light comes on.

Read: What Happens If The Car Engine Coolant Is Low?

Faulty valve or Carburator Issues

A car needs a mix of air, fire, and gas to run. Modern cars have an air control value to make sure the mix of air to fuel is correct. It could freeze up in the winter if it is already going bad. Ice can form on it if your car doesn’t have the proper sealing to keep moisture out.

Older cars have carburetors that do the same thing. Sometimes, there can be ice clogging on the carburetor and that can cause a car to not start. This can be resolved by thawing out the carburetor and removing the ice. 

Read: Bad PCV Valve Symptoms and Fixes

Vacuum Issue/EGR leak

Vacuum hoses that are cracked or loose can cause problems with a car starting. It’s a good idea to check those as that is an easy fix. Cold weather can cause the rubber to expand and contract faster than other times and that could mean hoses wear out faster, are loosened, or crack. 

EGR is built into your car’s system but your car will take longer to warm up if it fails. 


Why does my car start sometimes but not other times?

It could be any number of things. Off and on starting indicate there could be a problem with the ignition switch, a fuel pump, battery cables, low fuel pressure or a starter. Pay attention and write down specific times your car won’t start. Has it been sitting overnight? What’s the weather? When did it start last? This type of information will help your mechanic determine the exact problem. 

Read: Does a Car Battery Drain Faster In Cold?

Why does my car refuse to start after sitting overnight?

This is a sign of a bad fuel pump. The fuel pressure drops while a car sits and then the engine isn’t getting enough fuel when you crank it. Make sure you keep enough fuel in it to crank it in the morning and then get your fuel pump checked if the problem persists. 

Read: Bad Fuel Pressure Sensor Symptoms

How do I know if my ignition switch is bad?

There are several symptoms of a bad ignition switch. The car won’t start at all, the key won’t even turn and there is a noise from the starter. You may have some dashboard lights that flicker too. 

Why is my car slow in the morning?

Cooler temperatures can lead to your car battery producing less power and that can cause your car to be harder to start and slower to move in the morning. The cold can also make your oil thicker and that puts stress on the battery until the oil warms up and flows freely.

What is a cold start?

A cold start refers to starting your car when your engine is colder than its normal operating temperature. There’s debate on whether you should let it idle before driving it or just go. Some say its best for the car to drive it immediately so it reaches its best temperature quickly while traditionalists say its best to let it idle and warm up before putting it under the stress of driving.

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