How to Jump Start a Car With Jumper Cables

A jump start uses a working vehicle’s battery to provide enough power for a car with a weak or discharged battery to start. Before connecting anything, check both vehicles’ owner’s manuals: battery locations, approved jump points, and instructions can differ. If either manual says not to jump start the vehicle, use roadside assistance instead.

What You’ll Need

A set of insulated jumper cables in good condition, with clearly marked red and black clamps.
A second vehicle with a compatible 12-volt system, or an approved jump-start power pack. Do not assume a hybrid or electric vehicle can provide a jump; check its manual.
Safety glasses and gloves if available. Keep metal jewelry away from the battery and clamps.
Your vehicle’s owner’s manual, so you can identify the correct battery terminals or designated jump points.

Do not attempt a jump if a battery is cracked, leaking, swollen, unusually hot, or giving off a strong sulfur-like odor. Keep flames, cigarettes, and sparks away from batteries. If you are uncertain about the setup, contact roadside assistance.

Step-by-Step

Park safely. Move the vehicles close enough for the cables to reach, but do not let them touch. Put both in Park (or Neutral for a manual transmission), apply the parking brakes, switch off the ignitions, and turn off lights and accessories. Keep people clear of the engine bays.
Check the connection points. Read both manuals and identify the positive terminal or positive jump post and the negative or approved ground point. Remove keys or keep key fobs away as the manuals direct. Do not jump a frozen battery, and never use a visibly damaged one.
Attach red to the disabled car. Clamp one red cable end firmly to the disabled vehicle’s positive (+) terminal or designated positive jump point. Make sure the clamp cannot slip or touch metal nearby.
Attach the other red end. Connect the other red clamp to the working vehicle’s positive (+) terminal or designated positive point.
Connect black to the working car. Attach one black clamp to the working vehicle’s negative (−) battery terminal, unless its manual specifies a different point.
Ground the final black clamp. Attach the remaining black clamp to the disabled vehicle’s designated ground point, if provided. Otherwise use an unpainted, solid metal engine or chassis point away from the battery, belts, fans, and fuel components. Do not connect this last clamp to the dead battery’s negative terminal unless the vehicle manual specifically instructs you to.
Start the working vehicle. Start it and let it idle for a few minutes. Keep the cables and hands clear of moving parts. Do not rev the engine unless the vehicle manual calls for it.
Try the disabled car. Start it using its normal procedure. If it does not start after a brief attempt, wait a few minutes and try again. Avoid repeated long cranking, which can overheat the starter or cables. Stop if the cables get hot, smoke appears, or you hear unusual noises.
Disconnect in reverse order. Once the disabled car is running, remove the clamps in this order: black from the grounded point on the disabled car, black from the working car, red from the working car, then red from the previously disabled car. Keep clamps from touching each other or any metal.
Let the car run and get the battery checked. Follow the manual’s guidance on how long to run or drive the vehicle. A jump may get the engine started but does not confirm that the battery or charging system is healthy. Arrange a battery and charging-system check if the car soon fails to start again.

Common Mistakes

Reversing positive and negative. Red goes to positive and black to the specified negative or ground points. Reversed polarity can damage vehicle electronics and create sparks. If you are unsure, stop and recheck the markings and manuals.
Making the final connection at the wrong place. On many vehicles, the final black clamp should go to an engine or chassis ground away from the battery. Follow the manual’s exact instructions; battery layouts and approved points vary.
Letting clamps touch. Do not allow clamps to contact each other or the wrong terminal while connected. Arrange cables so they cannot fall into belts, fans, or other moving parts.
Jumping an unsuitable vehicle or battery. Not every vehicle can safely supply or receive a jump. Check compatibility, especially with hybrids, electric vehicles, and cars with remote battery posts.
Cranking continuously. Long, repeated attempts can overheat the starter and cables. Use short attempts with pauses, then stop and seek help if the engine still will not start.
Assuming a jump fixes the cause. A discharged battery may be old, faulty, or unable to hold a charge; an electrical or charging-system problem can also be responsible. A jump is a temporary start, not a repair.

Tips

Lay out the cables before connecting them and trace each end so the red and black clamps do not get mixed up.
Use designated remote jump terminals when the vehicle provides them. Some batteries are located in the trunk or under a seat, while jump posts may be under the hood.
Keep the donor vehicle’s engine at idle unless its manual says otherwise. Higher engine speed is not a substitute for correct connections.
After disconnecting, secure the cables so they cannot contact hot engine parts. Close the hood only after checking that tools and cables are clear.
If your car repeatedly needs a jump, have the battery and charging system inspected rather than relying on regular jump starts.

Troubleshooting

The disabled car does not crank: Turn both vehicles off and verify that every clamp is firmly attached to the correct terminal or ground point. Check that the donor vehicle is running and that the cables are in good condition. If there is still no response, stop; a loose connection, failed starter, or other fault may need professional attention.

The engine clicks but will not start: Check the connections and wait a few more minutes with the donor car idling, then make one brief attempt. If clicking continues, the battery may be too depleted or damaged, or the starter may have a problem. Do not keep cranking.

The engine starts, then stalls: The battery may not be holding charge, or the charging system may not be working correctly. Avoid switching the engine off in an unsafe location; arrange assistance and have the vehicle checked.

Cables spark, heat up, or smoke: Stop immediately. Do not touch hot clamps or continue the attempt. If safe, switch off both vehicles and seek professional help. A small spark can occur when making the final connection, but repeated or heavy sparking is a reason to stop and recheck the setup.

The cables will not reach or the battery is inaccessible: Do not stretch cables across traffic or improvise with extra wires. Reposition vehicles safely, use the vehicle’s designated jump posts, or call roadside assistance.

Frequently Asked Questions

How long should I leave the cables connected?

After starting the working vehicle, wait a few minutes before trying the disabled car; the right timing depends on the battery and vehicle. Follow the manuals, and avoid long or repeated cranking attempts.

Can I jump-start a car in the rain?

Wet weather does not change the connection order, but avoid standing water and do not handle damaged cables or exposed electrical parts. If conditions make the connections unsafe or hard to see, wait for roadside assistance.

Can a hybrid or electric vehicle jump-start another car?

Only if its manufacturer explicitly allows it and provides instructions. Some vehicles can receive a jump for their 12-volt system but must not be used to start another vehicle.

Why is the final black clamp connected away from the battery?

A designated ground point or suitable engine metal keeps the final connection away from the battery, where a spark could ignite battery gases. Use the exact point specified in the vehicle manual.

Should I replace the battery after a jump?

Not necessarily. A discharged battery may recover, but a battery that repeatedly goes flat or will not hold charge needs testing; the charging system may also need inspection.

Can I remove the cables while the engines are running?

Usually, the disabled vehicle should be running before you disconnect, but follow both manuals. Remove the clamps in reverse order and keep them from touching metal or one another.

Further reading: National Highway Traffic Safety Administration. Details can change, so check the official page for anything that matters to you. Spotted a mistake? Tell us. How we write an answer.