How to Find the Number One on a Distributor Cap

by Desdemona Delacroix
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A vehicle's ignition system is composed of several parts that work together to make your engine start smoothly. The distributor is part of the ignition system on a fuel-injected engine, and its job is to "distribute" electricity to the spark plugs. While performing maintenance on your ignition system, you should remove the distributor cap in order to clean the contacts or replace the cap. But when you put a distributor cap back on, it must be done a certain way.

The Basics

Step 1

Become familiar with your distributor before you take it apart. It looks like a cup with spikes on top.

Step 2

Picture the distributor cap as a crown that a king would wear. The points of the crown are where the distributor is connected to the spark plugs by spark plug wires. Each point connects to one spark plug, and each spark plug goes to one cylinder in your engine. So a six-cylinder car will have six contacts on the distributor.

Step 3

Find the rotor inside the distributor under the cap. The rotor spins around like a helicopter rotor and as it spins, it transfers electricity to the points of the cap. The electricity then moves through the spark plugs to the engine cylinders.

Line up the number one spark plug. The number one spark plug terminal is supposed to be the first one to fire as the engine cycles. In order for that to happen, the rotor needs to be lined up with the number one spark plug terminal when the piston is in the top dead center position during the compression stroke.

Finding the Number One

Step 1

Look on the distributor cap. Some manufacturers label the number one terminal.

Step 2

Follow the wire from the number one cylinder to the distributor cap. It will be connected to the number one terminal.

Step 3

You can also find the number one terminal by turning the engine manually until the timing marks on the camshaft and crankshaft are lined up. Once this is done, the rotor inside the distributor will be pointing to the number one terminal.

Purchase a repair manual for your vehicle. A variety of repair manuals can be found online.

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