How to Replace an Ignition Coil: 9 Easy Steps

how to replace an ignition coil

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It is not necessary to replace the ignition coil of your car unless it is showing signs that it is faulty. We’ve covered the symptoms of a bad ignition coil in a previous article, and we’ve mentioned how you can test the ignition coils by yourself.

This article will cover how to replace an ignition coil at home, as well as how much would it cost if you take it to a mechanic.

When to replace an ignition coil?

There could be a lot of issues pointing to a damaged ignition coil, and you should replace it only if you are sure that the ignition coil is the culprit.

But how can you be sure about it?

The first thing to check is the signs. If you have an ignition coil that needs replacement, your car will be showing a lot of signs, like poor fuel economy, starting problems, engine backfiring, stalling, misfiring, and trouble or power loss when accelerating.

However, these symptoms do not exclusively prove that your ignition coil is faulty. It just indicates that something is wrong with your ignition system, and it could be due to a damaged spark plug also.

To make sure that the ignition coil is faulty, you have to check the spark plug. It just takes less than three minutes and we’ll explain how.

  • Turn off your car and open the hood.
  • Try to locate the spark plug. It will be attached to the combustion chamber and a wire will be connected to it.
  • Gently pull the wire off one of the spark plugs, and remove the spark plug by rotating it anti-clockwise.
  • Connect the wire back to the spark plug.
  • Keep the other end of the spark plug close to a metal part of the car.
  • Remove the fuel pump relay.
  • Have someone turn the ignition key on for you. If you see continuous blue sparks being generated between the spark plug and the metal part, your ignition coil and the spark plug are fine.
  • If you don’t see blue sparks, or if there is a long gap between the sparks, repeat the same procedure for other spark plugs. If the problem persists, the ignition coil is faulty. If it is with just one spark plug, the spark plug is damaged and should be replaced.

Once you are sure that the ignition coil is damaged, you should replace it as soon as possible. An ignition coil replacement might solve the problem now, but not replacing it can cause severe problems to the car engine and the catalytic converter over time.

How to replace an ignition coil?

1. Make sure that you have all the tools required.

Keeping your service manual with you will help you when replacing the ignition coil since it will have specific instructions and tools required to accomplish this task. If you have it, make sure you read it twice before proceeding.

The tools required include a replacement ignition coil, screwdrivers, socket set, ratchet, and as mentioned, your car’s service manual. You may also use rubber gloves and dielectric grease.

2. Disconnect the battery.

Since the ignition coils deliver power to spark plug from the battery, it is necessary to disconnect the battery to avoid short circuit and possible damage to other electrical systems.

A socket or wrench can be used to disconnect the clamp bolt holding the cable to the negative terminal. Only one of the clamps has to be removed, and remember to tuck the cable down the battery side. This will avoid accidental touching of the cable with the negative terminal and possible short circuit.

3. Locate the ignition coils.

The service manual will be helpful to locate the ignition coils, but on a general note, you can find them on the top surface of the engine. If your car has a distributor, the wire in the distributor cap should lead you to the ignition coil.

For a car with coil packs, the ignition coils can be found next to the valve cover. Some car models have coil-on-plug, which means that the ignition coils are mounted above each spark plug. Some others have them mounted next to the spark plugs too.

4. If there are more than one ignition cables, label them.

Most of the cars have separate ignition coils that deliver electricity to multiple cylinders, but there are some cars with one ignition coil delivering power to different cylinders.

If there are multiple cables from a single ignition coil, number the cables from left to right using a marker. It is better to retain the original arrangement when connecting them back.

5. Disconnect the cables.

Since we do not disconnect the cables in a long time, they could have stuck to the coil. To ensure that the cables do not break while removing, hold them close to the ignition coil, squeeze and gently pull upwards. It is important to hold the cables closer to the ignition coil to avoid damaging them in the process.

If there are multiple cables, remove each one of them after labeling them correctly. Tying them together will avoid any hassles when replacing the ignition coils. You don’t have to worry about them mixing up if you have labeled them.

6. Remove the ignition coil

If you check the side of the coil, you will see an electrical plug going into the ignition coil. To remove it, press the clip that secures the plug to the coil and gently pull it backward. The plug should come off and we can proceed to replace the ignition coil.

The coil is attached to the engine using multiple bolts and screws, usually, it is a 4-bolt configuration. Pick the correct sized wrenches or sockets to ensure safe removal.

Once you have removed all the screws and bolts, grab the top of the ignition coil and pull it outwards. It might have stuck there due to dirt accumulation, but if it is harder than it should be, check if you have missed any screws or bolts.

Compare the old ignition coil with the replacement part. The connectors, holes for the bolts, shape, etc. should match exactly with the old one for smooth installment and perfect working of the engine. If there is any kind of mismatch, especially in the holes for the bolts or the shape, you should return it without thinking twice.

7. Install the new ignition coil carefully.

If you have a coil-on-plug system, apply some dielectric grease at the end of the coil. This will prevent moisture and the spark plug from sticking to the ignition cable boot.

The orientation of the ignition coil is important while replacing. The holes for the bolts have to align perfectly. Put each of the bolts and tighten them by hand first, and then use the wrench and socket to finish tightening.

8. Connect the plug and cables back.

We’ve removed a plug from the ignition coil side, and it’s time to connect it back. Slide the plug into its port by pushing it gently, and you should be hearing a release click when its in place. If you don’t hear the click, check if there’s any debris, remove it and connect the plug back.

Once you have done it, turn to the cables. Apply dielectric grease on the ports (and cables) labeled earlier to get a strong connection. If there was only a single cable, press it on to the new ignition coil’s port until you hear a sound.

If there are multiple cables, connect them one by one, starting with the one we labeled as number 1. Double-check the connections, if they are in proper order.

9. Connect the battery and start the engine.

Put the cable you removed in place and tighten it with an open-ended wrench or socket. Most of the batteries will have a plastic cover for the terminal, keep it in place and make sure you don’t touch the terminals.

Once all the connections are set up, start the engine, or have someone turn the ignition key on for you. If the engine does not respond at all, either the battery is dead, or the cable is not connected properly.

If the engine makes an attempt but fails, you must check the connections on the ignition coil.

Even if the engine works great, it is better to check all the cables(without touching it), if they are creating any sparks at the connection. A spark means improper connection.

How much would an ignition coil replacement cost?

An ignition coil replacement will cost anywhere between $220 to $350, depending on your car model and make. Labor costs are between $60 to $80 on an average and an ignition coil costs between $150 to $260. Luxury or sports car parts will cost a lot more than this.

While the overall cost might depend on your car model and the mechanic you go to, it should be noted that it can cost around $300 on average.

Sources:

  1. How to change an ignition coil – Wiki How
  2. How to replace an ignition coil – Your Mechanic
  3. How to replace an ignition coil – Doityourself