Checking The Secondary Ignition System

The secondary ignition system consists of the secondary side of the ignition coil, distributor cap, distributor rotor and ignition wires.

In most cases the distributor is mounted on the cylinder head and is driven by a gear on the camshaft. Most times it contains no electrical components other than the rotor and distributor cap, and its sole function is to transmit high voltage to the spark plugs in the correct firing sequence. Proper spark advance is fully automatic, and is provided by a load table built into the ECU.

With the distributor cap, look for cracks and carbon tracking. Sometimes they will be hard to see so you have to look closely and carefully. Look at the metal contacts inside the distributor cap. If there is a build up of crud clean it off or better yet, just replace it.

Look at the rotor. Many times the center of the rotor will burn through and the spark will go to the distributor shaft instead of to the spark plugs.

Check the ignition wires for cracks and burns. If there is no obvious take a spray bottle of water and spray the ignition wires while the car is running, you will see and hear the spark it if there are any cracks in the wires or wire boots. Doing this in the dark will make the sparking more obvious. If they look good, check them with an ohmmeter. General rule of thumb is no less that 200 ohms and no more than 310 ohms per inch.

Next remove and look at the spark plugs. Look for cracks in the porcelain insulators. Also look at the tip and electrodes of the spark plugs. The color and condition will tell you a lot about what's happening in your engine.