Caps and rotors
If you have an older car, chances are that one tune-up item you need to pay particular attention to is your ignition system. One item you don’t see too often anymore is the distributor. Most cars, these days, have long since transitioned to distributorless ignition systems, thus simplifying the tune-up process. But, if you’re maintaining a car with a distributor ignition system, it isn’t too hard to add this to the list of items you need to take care of.
First off, where are the common wear points in a distributor-based ignition systems? Primarily, you’re looking at two different parts – the distributor cap and the rotor. The distributor cap is exactly what it sounds like – a cap that fits over the distributor. It’s easy to identify, if you haven’t seen one before. Follow the spark plug wires to where they meet up, and you’ve found the distributor cap. Once you unclip it and lift off the cap, you’ll find the rotor. The rotor sits atop the distributor shaft, and rotates with the engine. The rotor, combined with the cap, is responsible for getting spark to each spark plug in the correct order. In fact, that’s where the distributor gets its name – it distributes the spark.
It’s impossible to tell from the outside if your cap and rotor are worn, except perhaps by observing suffering engine performance. In order to inspect them, you need to unclip and lift off the cap and inspect the contacts inside it, as well as those on the rotor. Visible scoring is a sign of wear and indicates that it’s time to replace them.
Thankfully, the distributor cap and rotor are two of the easiest maintenance items to replace in your engine. Replacement doesn’t even require tools. However, make sure to note which spark plug wire goes to which contact on the distributor cap. If not, it’s easy to mix them up, and if you do, your engine may not start. If it does, it’ll undoubtedly misfire.
While you’re replacing your cap and rotor, it’s a good time to replace your spark plugs. Also, take a look at your ignition wires. If you’ve noticed the car hesitating on a damp morning, only to behave normally after a moment or two, you probably have worn wires. If you’re not sure, start the engine while it’s dark and mist the wires with a spray bottle of water. If you see sparks, you know it’s time to rep
With a little attention, your ignition system should keep going for a long time. It’s easy to inspect, and it’s a good idea to do so if you’re not sure when it was last serviced.