Automotive Electrical and Electronic Systems Classroom Manual Fifth Edition Update by John F. Kershaw

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.
- -
-
BATTERY
+
GROUND
SIDE
POSITIVE (+)
-
SPARK
PLUG
+
-
CENTER
ELECTRODE
NEGATIVE (-)
COIL
TO
IGNITION CONDENSER
MODULE
BREAKER
POINTS
Figure 11-41. When coil connections are made
properly, the spark plug center electrode is electrically
negative.
Figure 11-39.
the distributor.
Toyota mounts the ignition coil inside
DISTRIBUTOR CAP
AND 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.
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 Rotor
A rotor is made of silicone plastic, bakelite, or a
similar synthetic material that is a very good insulator.Ametal
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