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TM 9-8000
Figure 15-15. Twin-Ignition System
wearing down of the rubbing block, which causes them
and a pickup unit. The reluctor replaces the distributor
to lose their adjustment.
cam used in the conventional distributor. The pickup unit
is made up of a permanent magnet, a pole piece, and
the coil.
Solid-State Ignition (Fig. 15-17).
c. Operation.
a. General. The recent rise of electronic ignition
systems is due to the superiority of electronic ignition
(1)  The ignition primary circuit is connected
over  conventional  ignition systems in several major
from the battery, through the ignition switch, through the
areas.  These systems totally remove one area of
primary side of the ignition coil, to the control unit where
maintenance from the ignition system, that of the ignition
it is grounded. The secondary circuit is the same as in
(contact) points.  Also, because the electronic ignition
the conventional ignition system.  The magnetic pulse
system produces a higher voltage than the conventional
distributor also is connected to the control unit.
system, the electronic ignition system usually can fire a
fouled spark plug. In the area of high performance, the
(2)  As  the  distributor  shaft  rotates,  the
electronic ignition system is far superior in that its voltage
distributor reluctor turns past the pickup unit, and each of
does not deteriorate as quickly at high engine speeds as
the eight teeth (on an eight-cylinder engine) on the
the conventional ignition system. Because the electronic
reluctor pass near the pickup unit once during each
ignition system does not contain ignition points that wear,
distributor revolution. As the reluctor teeth move close to
ignition performance does not deteriorate with mileage.
the pickup unit, voltage is Induced into the pickup unit.
That is, as a tooth on the reluctor passes the pickup coil,
b. Description.
The electronic ignition system
magnetic lines of force flow from the permanent magnet,
differs from that of a conventional ignition system in that
through the pole piece, and through the reluctor back to
it consists of a special pulse sending distributor, an
the magnet. Voltage is induced in the windings as these
electronic control unit, a two-element ballast resistor, and
a special Ignition coil. Also, the ignition breaker points
and capacitor used in the conventional ignition systems
have been replaced by a gear like piece called a reluctor


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