ker88839_ch11.qxd
1/9/06
11:31 AM
Page 247
The Ignition: Primary and Secondary Circuits and Components
247
Figure 11-40. The Buick C31 distributorless ignition uses a single coil pack with three coils, each of which serves two cylinders 360 degrees apart in the firing order.
-
-
GROUND SIDE POSITIVE (+)
+
BATTERY
-
+
-
CENTER ELECTRODE NEGATIVE (-)
-
COIL
SPARK PLUG
TO CONDENSER IGNITION MODULE BREAKER POINTS
Figure 11-41. When coil connections are made properly, the spark plug center electrode is electrically negative.
Figure 11-39. Toyota mounts the ignition coil inside the distributor.
The rotor mounts on the distributor shaft and rotates with the shaft so the rotor electrode moves from one spark plug electrode to another in the cap to follow the designated firing order.
DISTRIBUTOR CAP AND ROTOR
Distributor Rotor
The distributor cap and rotor, Figure 11-43, receive high-voltage current from the coil secondary winding. Current enters the distributor cap through the central terminal called the coil tower. The rotor carries the current from the coil tower to the spark plug electrodes in the rim of the cap.
A rotor is made of silicone plastic, bakelite, or a similar synthetic material that is a very good insulator. A metal electrode on top of the rotor conducts current from the carbon terminal of the coil tower. The rotor is keyed to the distributor shaft to maintain its correct relationship with the shaft and
