Why Your Car Won't Start When Cold and What to Do
Freezing temperatures can prevent your car from starting. Here are the three main reasons:
- Battery performance goes down. Cold temperatures slow down the chemical action between the battery electrolyte and the plates, reducing battery power. This means that battery current decreases as temperature decreases, starving the starter motor from much needed power.
- Engine oil thickens. At the same time, engine oil turns into a cold-syrupy substance that won't flow as easily, much less through small clearances of around 0.002" (0.05mm) within the engine, causing too much friction around components that need to move at high speeds.
- Engine power needs increase. As the temperature goes down, engine demand for starting power increases. Low temperatures stress mechanical components. Since oil won't flow easily, crankshaft, pistons, and valve train components will experience higher friction.
As you can see, battery operation, oil efficiency, and engine mechanical performance all have one thing in common: They all need an adequate temperature to start working without problems.
Even more, your battery's age, plus poor maintenance and wear of components in the charging and starting systems will affect the engine's ability to start at freezing temperatures.
The following graphic can show you this relationship more clearly.
Note: If at cold temperatures your engine turns over at its normal speed—or close to it—but won't start, your problem may be in the ignition system (worn spark plugs or wires) or fuel system (clogged fuel filter, or frozen droplets of water in the fuel line).
I. How Can I Start My Engine in Cold Weather?
- Check the battery
- Check battery connections
- Check battery electrolyte
- Check the battery and solenoid for voltage
- Increase battery temperature
- Replace the battery
II. Help Your Car's Engine Cope With the Freezing Winter
Warning - Don't Charge a Battery When Frozen!
Don't try to charge a battery if you think it is frozen or has ice in it. Charging a frozen battery can not only burst the case open, but may cause an explosion from internal pressure. Instead, allow the ice to melt and battery temperature to rise.
I. How Can I Start My Engine in Cold Weather?
There's little you can do to straight off reverse the effects of cold weather on an already ice-cold engine. But here are a few things you can do that may help your engine start.
When you try starting the engine, it may not turn over (the engine doesn't move at all). You may hear instead a series of clicking noises. This could be a sign of a discharged battery, loose or corroded battery cables, or some other starting system problems.
1. Check the Battery
- Turn on the headlights. If they are bright, almost normal, you still have some battery charge; if not, the battery charge may be low. Continue with the next steps.
- Turn the ignition key to the On position for about 8 seconds, but don't start the engine. Repeat the process one or two more times and try to start the engine. Fuel pressure may need a little help.
- If nothing happens, take a look under the hood. If you see signs of corrosion around one or both terminals, or they feel a little loose when you twist them, that could be your problem. Remove corrosion from the cables and terminals (see the following section), or tighten the cables with a wrench.
- If everything seems fine, probably the battery has run down. If your battery is good, try jump-starting the engine. Ask a neighbor, friend or car shop to help you start your car. In most cases, this will get you moving. If your vehicle has specific jump-starting points, consult your car owner's manual.
As your battery ages, its chances of coping successfully with cold temperatures diminish as well. On average, a battery's service life is four to five years, htough some manufacturers recommend replacing the battery every three years. If your battery is already reaching the end of its service life, you may want to install a new battery now.
2. Check Battery Connections
During the summertime, you may get away with a little corrosion between the battery terminals and the battery posts. Not during the winter. Corrosion acts like electrical resistance, and you need every bit of juice you can squeeze out of your cold battery.
Sometimes, corrosion hides between the inner side of the terminal and the battery post. If you haven't checked the terminals recently, now is the time:
- Disconnect the battery terminals (negative first, then the positive side) using a wrench.
- If necessary, prepare a solution of 8 oz of warm water and a tablespoon of baking soda in a disposable cup. Thoroughly mix the solution.
- Dip the battery terminals in the solution for a few seconds and use a soft brush to remove corrosion from the terminals. If necessary, use a wire brush to remove corrosion.
- Use the soft brush to clean the battery posts as well. Wipe the posts clean with a clean rag.
- Also, wipe the top of your battery clean, if necessary. Using the solution of warm water and baking soda mixture, apply the solution with a soft brush and wipe it clean using a clean rag. Don't allow the solution to seep under the battery caps.
3. Check Battery Electrolyte
- On a battery with removable caps, wipe clean the battery top with a shop rag to prevent debris from falling into the battery cells before removing the caps.
- Remove the caps using a flat head screwdriver and check the electrolyte level.
- The electrolyte should reach the bottom of the filling rings. If not, add the necessary amount of distilled water to each cell.
4. Check the Battery and Solenoid for Voltage
Sometimes, the problem is that either your battery or a connection in the starting system, is preventing the necessary current from reaching the starter motor. The engine won't crank when you turn the key to start the engine.
- Check that your battery has 12.4 volts or more. Measure battery voltage across the battery posts with your voltmeter. If you get less than 12.4 volts, you need to charge your battery.
- On the starter solenoid, connect your voltmeter red lead to the S (starting) terminal, and the meter black lead to battery ground (-). You should get at least 12 volts when the ignition key is turn to start the engine; otherwise, there's a loose or corroded wire along the way in the ignition part of the starting circuit.
- If everything seems fine at this point, it's a good idea to do a voltage drop test on the system. A starter-system voltage drop test will be more accurate and a faster way to find the part of the circuit with the fault, if your are suspecting a circuit problem in the starting system. Don't forget to do a voltage-drop test on the ground side of the circuit as well. Many circuit problems are due to poor grounds.
Check the charging system as well, if necessary.
5. Increase Battery Temperature
If at all possible, you can try removing the battery and bring it indoors to warm it up.
- Disconnect the negative battery cable first and than the positive terminal from the battery.
- Disconnect the battery hold-down or retainer.
- Bring the battery into a room, away from the cold weather, and wrap it in an old blanket or cover for a few minutes to bring its temperature up a bit.
- Reinstall the battery and try starting the engine.
6. Replace the Battery
As your battery ages, its chances of coping successfully with cold temperatures diminish as well.
On average, a battery service life is about 4 to 5 years. If your battery is already reaching the end of its service life, you may want to replace the battery now.
A brand new battery has a better chance to withstand cold weather and help your engine fire up.
II. Help Your Car's Engine Cope With the Freezing Winter
To avoid getting stuck during the freezing months of winter, there are several things you can do. Buy special car accessories, make sure you have adequate tools, and prepare your engine for the chilling temperatures ahead of time.
Your local or online auto parts store may carry special accessories and tools that can help your car survive the winter months. Some things you may want to consider:
- battery blanket
- electric engine warming blankets
- oil heater
- block heater
- battery booster
- battery (trickle) charger
- jumper cables
- winter emergency kit
Yes, even a carport will help to keep your car a little warmer during a snowy night or day.
- Use the appropriate engine oil for the winter months in your area. Consult your car owner's manual, with your local car shop, dealer or auto parts store. For example, if you use 10W-30 engine oil during the summer, you may need to switch to 5W-20 for the winter months, or even a 0W grade (a very thin oil), specially useful in freezing cold, sub-zero temperatures.
Make sure the coolant has the correct strength to protect your engine from the freezing temperatures in your area. Consult your car owner's manual, your local shop or auto parts store.
A 50/50 mixture of antifreeze and distilled water is appropriate for most weather conditions. But you need to make sure your antifreeze has your engine covered for at least 20 degrees lower than the lowest temperature in your area. For example, if the normal lowest temperature in your area is around 20 F (-6.6 C), your coolant should have a freeze-up point of 0 F (-17.6 C).
You can use a to test your coolant. You simply draw coolant into the tool's reservoir by squeezing a rubber bulb and the tool will show the current freeze-up protection of the coolant in your vehicle. Follow the instructions that come with your tool. hydrometer
- Keep your fuel tank over half full during the freezing cold temperatures. This minimizes condensation and the chances of clogging fuel lines. Although this might be less of a problem now, as anti-icing agent is added to the gasoline to avoid fuel line freeze-up during the winter season. If the gas you are using doesn't come with this additive (check at your gas station), you can buy a bottle of dry gas at your local auto parts store and add it to your tank.
- Service the charging, ignition and starting systems as necessary.
- Check the battery. Make sure the battery is clean and has enough electrolyte
- Inspect the belts. A good and properly adjusted drive belt is critical for the operation of the alternator.
- Check the charging system operation. Make sure it is properly charging the battery.
- Check the starting system operation. Inspect starting system connections and look for signs of corrosion and loose wires that may prevent the battery to deliver power to the starter motor.
- Check the ignition system. Make sure you are getting a good spark. Replace spark plugs and wires as necessary.
- Check battery and engine grounds. Loose or corroded engine ground connections will make current difficult to go through.
The following video shows how using a heating pad can help you start your vehicle when it is cold.
This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.
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© 2019 Dan Ferrell