Car won’t start in the freezing cold? Here’s Why, and what to do

Winter weather is tough on cars, and on their drivers. The temperature drops below freezing and  you get in one chilly morning and turn the key, only to find your vehicle won’t start. What are you supposed to do? 

Let’s take a closer look at what winter does to your vehicle, the main reasons your car won’t start, how to deal with it when it happens, and things you and your mechanic can do to prevent these problems from happening the next time. 

Why cars and cold weather don’t get along

We tend to think about our vehicles as machines, but there’s also a lot of chemistry involved. Car problems related to the cold are usually caused by a combination of chemical and mechanical malfunctions. Here are some common problem areas.

Your battery

A battery that worked fine during the spring, summer and fall can fail as the mercury drops. This is because your battery runs on a chemical process, one that gets slowed down by low temperatures. The colder it gets, the less power the battery will produce.

If your battery’s condition is marginal, it may not be able to start your vehicle as temperatures drop toward single digits. When you turn the key, you may hear the starter running very slowly, or not at all.

If you think your battery might be at fault, kill everything else that would draw power from it. Turn off the lights, the heater and the stereo. Unplug any phone chargers. And, if you have a manual transmission, hold the clutch down.

Now turn the key in the ignition, or push the start button. Hold it for about 10 seconds, but no longer. If all goes well, your engine should start. If not, wait a few minutes and try again.

If this doesn’t work, you can try to tighten or clean your battery cables, or get a jumpstart. Another idea if you have some time: Remove the battery and take it indoors where it can warm up. Failing everything else, you can always get a tow to your mechanic.

Your fuel

If you turn the key and the engine cranks like it usually does — but doesn’t start — your problem could be fuel-based, as opposed to being a battery issue. 

There are a couple ways that cold weather can affect the gas in your car. First, gasoline must be vaporized before it can be burned, and lower temperatures make this harder. The second possible issue is condensation, which happens normally inside your gas tank as the outside temperature fluctuates — and the lower your fuel level, the worse it gets. Water is heavier than gasoline, so the water will migrate to the bottom of the tank and into the fuel lines. When the temperature drops below freezing, the water in the fuel lines can freeze and prevent gasoline from reaching the engine. 

Diesel-powered vehicles have their own wintertime issues. Diesel fuel can turn into a gel at low temperatures, preventing it from flowing into the engine. 

Older cars could have problems with their carburetors, which were common on most vehicles until the mid-1980s. They are mechanical devices that mix air and fuel, then feed the mixture into the engine, where it is burned inside the cylinders. A combination of poor fuel vaporization and ice clogging can produce starting problems in carbureted vehicles.

Most solutions to fuel problems involve getting your vehicle into a warmer environment, where above-freezing temperatures will eventually help. Typically, a tow will be needed.

Your engine oil

Another effect of low temperatures is a thickening of the oil inside your engine, which keeps it from flowing as well as it should. To get your car started, the starter motor has to try to spin all the moving parts of the cold engine — oil help lubricate these parts. But thicker oil creates more resistance. If the starter system can’t overcome this resistance, the vehicle won’t start.

Your oil can be too thick for a few different reasons. It may be a type that’s more suitable for summer use, or it could be that you haven’t changed your oil in a long time — oil thickens as it ages.

You can check your engine’s dipstick to see if the oil level is low. If so, try adding some oil better suited to cold weather. This might be enough to get your car going.

How to keep your car going in cold weather

With some simple preparations before the cold weather hits, you can avoid most of these starting problems. Some of the steps are best left to your mechanic, and some are things you can do.

What to have your mechanic check

Your battery. Batteries eventually can deteriorate to the point where they just can’t get your car started in cold conditions. It’s better to know if yours is bad before it gets cold, so you can replace it with a new one that you can count on. The terminals where the wires attach should also be clean and tight. An electrical system check will also identify any other components that may not be operating at peak efficiency.

Your alternator. The alternator is the component that keeps your battery charged. A bad alternator could prevent your battery from gathering enough charge to start your car. The alternator should be replaced if it’s defective. The drive belts that turn the alternator should also be checked for slipping and wear.

Your starter system. If the starter has gone bad, it may be drawing too much current from the battery, preventing your car from starting. The starter relay, the solenoid and the ignition switch should all be checked for proper operation.

Your oil. Fresh oil that is designed for winter use is cleaner and slipperier than old, worn out oil. If your winters are really extreme (think Minnesota or Michigan), consider using synthetic oil, which is made to flow better at very low temperatures. Replace the oil filter, too.

Your fuel pump. You want to have the correct amount of pressure pushing fuel through the lines, when you are trying to get started in the cold winter weather.

Your spark plugs and their wires. Spark plugs last a long time these days, but they’re not immortal. Have your mechanic check them for proper operation so that they’ll be able to generate a strong spark and get your engine started when it’s very cold. 

Your coolant. You will need the proper mixture of coolant and water to protect your engine and keep the mixture from freezing at subzero temperatures.

What you can do

Keep the gas tank full. Excess empty space inside your tank will increase the amount of condensation that might freeze your fuel lines in extreme weather. Get in the habit of never letting it go below the half-full mark. This is also good insurance in case you get stuck or stranded and need to keep your vehicle’s heat and lights operating.

If you use diesel fuel, make sure that the fuel you use is “winterized,” meaning it’s been treated with an additive that keeps it flowing at low temperatures.

Keep your vehicle warm. Starting with a car that is at above-freezing temperatures will eliminate just about all of these cold-weather starting problems. If you have a heated garage, use it. Even an unheated garage can help, and if you use it safely, a small electric or kerosene heater can fend off the cold.

You can also buy an insulating cover to place over your hood to keep the engine heat in. Or you can try using a battery blanket to keep it warm. 

Another option is a plug-in engine-block heater, which uses a heating element to keep your engine’s coolant warm overnight. Ask your mechanic about a block heater if you have extreme winters and a place to plug it in. In addition, you can attach a trickle charger to your battery each night to keep it fully charged, without any risk of overcharging it. 

If your car starts, but only after a lot of effort 

Your car is running on borrowed time. At least one of the factors mentioned above is present in your vehicle right now. Get your car checked out and save yourself a frustrating, freezing morning — and maybe a tow, to boot. 


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