How to determine which spark plug wire goes where?
Content
After reading this article, you will no longer be confused by the numerous spark plug wires and where they go. This easy to understand guide will teach you how to tell which one goes where.
In general, to find out which spark plug wire goes where, refer to the spark plug wiring diagram in your vehicle owner's manual, or open the distributor cap to check the distributor rotor and locate the first ignition terminal. It is vital to know the correct IGNITION ORDER and direction of rotation of the rotor.
I will go into more detail in my article below.
Where are the spark plug wires?
The spark plugs are usually located on the cylinder head (next to the valve covers). The other ends of the wires are connected to the distributor cap. In new cars, ignition coils can be seen instead of a distributor cap.
Are the spark plug wires numbered?
Numbered spark plug wires help determine which one goes where, but this is not always the case, and the order in which they are located is not necessarily sequential. Another clue to understanding the order may be their different lengths.
Figuring out which spark plug wire goes where
There are two ways to find out which spark plug wire goes where:
Method 1: Check Spark Plug Wiring Diagram
The best way to find out how to replace the spark plug wire is to refer to your vehicle owner's manual. A detailed manual should include a spark plug wiring diagram to show exactly which wire goes where, i.e. the correct configuration.
An example of a spark plug connection diagram is shown below. If you don't have access to the manual, don't worry. We'll show you how to check the main body for all spark plug wire connections, called the "distributor cap".
Method 2: open the distributor cap
It would be helpful if you looked for the distributor of the ignition system in the engine compartment (see picture above).
The distributor cap is the round component containing all of the spark plug wire connections. Usually it is enough to remove a couple of latches with a screwdriver to open the cover. Under this cover you will see the "distributor rotor".
The distributor rotor rotates with the rotation of the crankshaft. The rotor can be manually rotated clockwise or counterclockwise (only in one of the two possible directions). Check which direction the distributor rotor in your car rotates.
Consequences of incorrect installation of spark plugs
The spark plugs are fired one at a time in a precise sequence called firing order.
If you insert them incorrectly, they will not fire in the correct order. Consequently, the engine will misfire in the cylinder. This can cause unburnt fuel to collect and flow out the exhaust pipe. The catalytic converter and certain sensors are the most susceptible to damage. In short, incorrectly inserted spark plugs will cause engine misfiring and cause damage to other parts of the engine.
Conversely, if your engine is misfiring, it could mean worn out spark plugs or misplaced spark plug wires.
Checking the spark plugs
When inspecting the spark plugs, they may need to be removed. Knowing which spark plug wire goes where comes in handy in these situations. Sometimes you may only need to replace a particular spark plug or spark plug wire, so it's important to know what needs to be changed. Here are some checks you can make:
Carrying out a general check
Before performing a physical inspection, disconnect the spark plug wires and wipe them clean. Then inspect the spark plugs in the following order:
- Looking at them individually, look for any cuts, burns, or other signs of damage.
- Check for corrosion between spark plug, insulating boot and coil. (1)
- Check the spring clips connecting the spark plug wires to the distributor.
Check spark plugs for electrical arcing
Before checking spark plugs for an electric arc, be sure not to touch the wires to avoid the possibility of electric shock. (2)
With all spark plugs on both ends, start the engine and look for any signs of arcing around the spark plug wires. If there is a voltage leak, you may also hear clicking sounds.
Conducting a resistance test
Note. You will need a multimeter to run a resistance test and set it up according to your car's owner's manual.
Remove each spark plug wire and place its ends on the multimeter test leads (as directed in the manual). You can safely reinsert the spark plug wire if the reading is within the specified range.
Replacing spark plugs
When replacing spark plugs, you must know how to connect them correctly. If done incorrectly, the engine may not start.
Replace spark plug wires one at a time
An easy way to connect the correct spark plug wires to the correct terminals is to replace them one at a time. You can also use a unique spark plug wire removal tool called a "T-handle" (see picture below).
If for some reason this is not possible, you will need to determine the first wiring terminal, find out what type of engine you have, know the correct ignition order for it, and whether the rotor rotates clockwise or counterclockwise.
Find the first firing terminal
It would be helpful if you found the first firing terminal. Inside the distributor, you will see the ends of four spark plugs connected to four terminals. With any luck, the first spark plug will already be marked with the number 1. This wire is connected to the first cylinder.
In a typical 4-cylinder engine, the cylinders may be numbered 1 to 4, and the first one is probably closer to the front of the engine.
Attach spark plug wires
After you have connected the first spark plug wire to the first cylinder, you will need to connect the rest of the spark plug wires in the correct firing order.
You can turn the distributor rotor to see where each spark plug wire goes. It will rotate either clockwise or counterclockwise (in one direction only). The second terminal will be connected to the second spark plug until you get to the fourth spark plug. See example below.
Firing order
Depending on your vehicle, the order of operation may be shown in the table below. To be sure, you should check the manual for your vehicle. Consider this information only as a possibility.
| engine's type | Firing order |
| Inline 3-cylinder engine | 1-2-3 or 1-3-2 |
| Inline 4-cylinder engine | 1-3-4-2 or 1-2-4-3 |
| Inline 5-cylinder engine | 1-2-4-5-3 |
| Inline 6-cylinder engine | 1-5-3-6-2-4 |
| 6-cylinder V6 engine | 1-4-2-6-3-5 or 1-5-3-6-2-4 or 1-4-5-2-3-6 or 1-6-5-4-3-2 |
| 8-cylinder V8 engine | 1-8-4-3-6-5-7-2 or 1-8-7-2-6-5-4-3 or 1-5-4-8-6-3-7-2 or 1-5-4-2-6-3-7-8 |
Example of a 4-cylinder engine
If you have a 4-cylinder engine, the standard ignition order will be 1-3-4-2 and the first ignition terminal (#1) will be connected to the first cylinder. After turning the distributor rotor once (clockwise or counterclockwise, but not both), the next terminal will be #3, which must be connected to the third cylinder. Doing this again, the next one will be #4 and the last one will be #2.
Take a look at some of our articles below.
- How to test a spark plug with a multimeter
- How to check the ignition coil with a multimeter
- How to prevent spark plug wires
Recommendations
(1) Corrosion - https://www.sciencedirect.com/topics/engineering/corrosion
(2) electric shock - https://www.mayoclinic.org/first-aid/first-aid-electrical-shock/basics/art-20056695
