by Marshall Brown

Created on: January 17, 2010   Last Updated: January 21, 2010

How often to change spark plugs:

Most manufacturers recommend spark plug wires to be replaced at intervals of five to seven years. (Every 60,000-100,000 miles.) If you have purchased a used car and are unsure of how old the wires are, you can easily tell just by looking at them for wear and tear. Another easy way to identify replacement wiring: on domestic vehicles, factory replacement wires don't usually have the corresponding cylinder number written on them, where the original set of wires will. On foreign vehicles, usually have cylinder numbers on both the original and replacement wires, along with date they were manufactured.

Locating your spark plug wires:

(With vans, you usually have to remove the engine housing from the inside of the cab, and the distributor is located on the rear of the engine.)Under the hood of your car or truck, you will see at the top of the engine, and usually to the rear of the engine, a round object (distributor cap) with thick rubber wires that run from it's top to the sides of the engine.  Where the wires connect to the engine, through the spark plugs are secured into the side of the block. This is the system responsible for starting the engine, known as the ignition system. Without any of these components performing properly, you aren't going anywhere.

Before removing old set of wires:

The first step your going to want to take is labeling which cylinder your spark plug wires go to on the distributor cap or making a sketch and labeling the diagram. There are various ways of doing this, the best is to label the wire and the block above the spark plug. If you have an automotive manual to the make and model of your car, things are much simpler. Another way to replace the wiring is one at a time.

The new set of spark plug wires:

As you will notice, the spark plug wires come in different lengths, this is because each corresponding wire must not have slack or it can cause the electricity to ground out by touching any obstructions. To start replacing your wires, you will want to start with the longest wires, furthest from the rear of the engine. (Be sure all contacts are clean on both the distributor cap and ends of the spark plugs.)

Installing the new spark plug wires:

Following the labels marked on your diagram or distributor cap, replace each wire with it's corresponding new replacement. Take note of length and shape. Once you have affixed the wiring to the distributor cap, plug each corresponding wire into it's appropriate spark plug. Be sure to avoid getting any grease, oil, or other contaminants into the spark plug casing of the wire. Once you have replaced the wiring, turn over your key. If your engine starts and runs fine, congratulations. If it doesn't start or backfires, make sure connections are secure and that each wire is appropriately linked to the right cylinder and the distributor cap. (Be sure to not allow the wires to rest on any metal, as this can effect performance.)

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