How to Change a Distributor Cap and Rotor

by William Zane
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Auto Engine image by Andrew Breeden from

The distributor cap and the rotor underneath the cap are very important aspects of your car's ignition system. The spark plug wires are connected to the distributor cap; and as the rotor turns with the engine's revolutions, it sends a signal to each spark plug wire as it passes by, sending spark to the engine's cylinders. Over time, distributor caps and rotors become worn out from continuous use. Replacement of these parts is considered part of routine maintenance and is a very easy task on most vehicles.

Step 1

Open the hood. Locate the distributor. It may help to have a shop manual for your particular make and model of car, but this is generally an easy part to find since it has all of the spark plug wires coming out of it and running to the engine's spark plugs.

Step 2

Remove the distributor cap without pulling the spark plug wires off. You can remove the plug wires if you want to, but be sure and label them as well as the distributor cap itself with a marker and a piece of tape so that the firing order of the motor is not disturbed. The cap may be fastened on in a couple of ways. Many caps have hinged clips fastened to the distributor itself that hold the cap on. These can be popped off by hand or with a flat head screwdriver. The cap may also be bolted on, in which case locate the bolts (or screws) and remove them with a socket or a screwdriver.

Step 3

Remove the rotor located under the distributor cap. The rotor is a plastic component that slides onto the distributor shaft. On many cars the rotor is removed by simply pulling straight up from the distributor shaft. More modern cars may have a small bolt or screw that holds the rotor in place and will need to be removed before the rotor can be pulled off.

Step 4

Slide the new rotor onto the distributor shaft in the reverse of removal by pressing it down onto the shaft. The rotor will have an indentation in it that ensures proper alignment with the shaft of the distributor. Reinstall the bolt or screw that holds the rotor in place if applicable.

Step 5

Transfer the spark plug wires from the old distributor cap to the new cap one at a time to avoid mixing up the timing order. When you remove the plug wires, pull them up from the base where they slide onto the cap and not from the wire itself to avoid damaging them.

Step 6

Reinstall the distributor cap in the same orientation that the old cap was installed. The cap will only go on one way that allows the clips or bolts to be properly fastened. Start the motor to ensure that it is running correctly and firing on all cylinders.

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