How To Connect Spark Plug Wires To Coils (Step By Step)

How To Connect Spark Plug Wires To Coils

To understand how to fit spark plug wires to coils, you have to understand how modern vehicles are wired. If you’re dealing with an older car–say, ten years, you may have a distributor.

Newer cars eschew the distributor in favor of an electronically controlled process.

So, how to connect spark plug wires to coils? Connecting the spark plug wires to a coil(s) isn’t difficult You just need to follow the steps below:

1.         Remove the old spark plug wire

2.         Remove the long boot from the spark plug end

3.         Now you reverse the process

4.         The same goes with spark plug boot as you slide it back down and in over the cylinder.

These are “plug-in” devices after all. However, some screw-in, require a little elbow grease or attach in different ways. Be sure to check your vehicle’s manual for a better understanding. 

The coil converts low-voltage from the battery to high-voltage before sending it through the spark/coil wires to the spark plug, where the electric charge starts the combustion process.

Some coils—in older engines—do this with a distributor.

The coil converts the voltage and sends it to the distributor. The distributor will generally have one coil wire per cylinder that turns to its own spark plug for that cylinder.

Newer vehicles replace the distributor with an electrical system that “distributes” the voltage to the proper cylinder/spark plug.

For instance, a newer car, that has a four-cylinder engine, may use two coils. Each coil may have two coil wires for a total of four.

Or it may have one coil with four wires. A six-cylinder can have three coils with two coil wires each, and so forth and so on. 

Step-By-Step Connection Process

No matter what type of vehicle you have, or what age it is, you need to look it over carefully to determine how many coils you have and where the coil/spark plug lines are running.

Placement of your spark plug/coil wires is every bit as important as replacing the part itself.

It’s also a good idea to mark the wires and make matching marks on the new ones you’re about to install.

How to make a spark plug wire or coil wire >> Check out the video below:

It wouldn’t do to run the wrong spark plugs to the wrong coil (if you have more than one). It’s best if you remove the old and install the new one at a time.

Before starting anything, remove the black wire from the negative terminal on the car battery. This will keep you from getting shocked or doing electrical damage to the vehicle as you’re working on it.

Also, make sure the engine is cool. It is not fun to route new spark plug wires on top of a hot engine. 

  1. Remove the old spark plug wire by twisting the L-boot at the ignition coil and pulling. Typically these are “snap-on” boots with a snap ring terminal inside the boot. 
  2. Remove the long boot from the spark plug end, over the cylinder. Never pull these out by the wire. Use a spark plug removal tool and always grab and pull from the boot only. Like the coil pack removal, twist (counter-clockwise) as you pull the boot up and out.
  3. Now you reverse the process. When you connect the new snap ring terminal boot onto the coil/coil pack, there should be an audible “snap” sound. If you don’t hear that sound when you press it down, it probably didn’t get seated properly.
  4. The same goes with spark plug boot as you slide it back down and in over the cylinder. The snap won’t be as audible, but you should press in hard until you “feel” it snap into place and it is seated flush against the engine.

Now, this is how the process works with the distributor cap, coil packs, or individual coils. It’s a little different with coil-over-plugs, as the entire thing is replaced.

But there are some things you need to pay attention to, depending on the type of coils you’re dealing with.

Different Coil Types: Coil Pack, Individual, Distributor Cap, or Coil-Over-Plug

Coil packs are usually labeled as to what terminal goes to which cylinder. You can open your vehicle’s manual to get an exact location for each cylinder so that you can correctly match the spark plug wires as you lay them out and connect them.

Individual coils

Are even simpler, as all you have to do is remove the spark plug wires one at a time, and connect the new spark plug wire to the now-empty coil and run it back to the spark plug over the cylinder.

Distributor caps

Are often not labeled at all. For a six-cylinder engine, you’ll have six spark plug wires connected around the perimeter of the top of the distributor cap.

Often, there will be an additional wire running to a terminal in the center of the distributor cap. 

The center wire runs to a single ignition coil and connects the same way. When changing spark plugs on a distributor cap, label them and remove them one at a time before replacing them one at a time.


Are the easiest and are predominantly found in newer vehicles. A coil-over-plug is the entire coil and plug mechanism that sits right over the cylinder—and is connected to the battery with a pin connector—instead of just the spark plug. 

To replace them, simply unplug the old one and twist it out, then press the new one in. Remember to plug it back into the pin connector. 

That covers all of the types of coils that you’re likely to encounter, going back roughly 20 – 25 years. They’re not especially difficult to replace. 

With the older ones, however, like coil packs and distributor caps, be careful to label and remove them one by one while replacing them in the same manner.

All Things Considered

Even with older vehicles, that go back a quarter of a century, you’ll find that spark plug wires connect easily with coil terminals. Snap ring connectors—an ingenious invention—make everything so much easier. 

While it’s not difficult to hardwire components together, it takes much longer and is problematic when working in extremely tight environments, such as under a car hood.

Some spark plugs are located in really difficult-to-reach areas, which makes up for the neat little snap link connectors.

Every time you do a tune-up and you’re snapping on each spark plug wire to its respective coil, be thankful that you’re not under there with a pair of crimpers and twist caps.

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Jeff is an automotive technician, technical writer, and Managing Editor. He has held a lifelong passion for cars, with a particular interest in cars like the Buick Reatta. Jeff has been creating written and video content about transportation, automotive, electric cars, future vehicles as well as new, used for more than 18 years. Jeff is based in Boulder, Colorado.

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