You must remove the distributor cap to to gain access to the rotor. Then remove the rotor to perform a visual inspection. The rotor should be inspected carefully for discoloration and other damage. When inspecting the rotor, check for the following items.
Inspect the rotor for damage and signs of high-voltage leaks. Courtesy of DaimlerChrysler Corporation.
- Rotor locating tab and hold-downs. All rotors have a means of assuring they are installed in the proper direction in reference to the distributor shaft. This tab also assures that the rotor turns with the shaft. If the tab is broken then the rotor may not spin with the shaft or not be located on the correct cylinder.
- Eroded rotor tip.
- Rotor spring arm. When the high voltage enters the distributor cap it then jumps to the spring arm of the rotor. The spring arm contacts the center insert of the cap, then directs the voltage to the rotor tip. If the spring arm is eroded away because of electrical arcing, it will increase the voltage required to fire the spark plug. If available voltage is not sufficient, the spark plug may misfire or not fire at all.
- Punch through. Inspect the top and bottom of the rotor carefully for grayish, whitish, or rainbow-hued spots. Such discoloration indicates that the rotor has lost its insulating qualities. High voltage is being conducted to ground through the plastic.
- Cracks in the rotor. A cracked rotor must be replaced.