electrical control portion of the ignition pulse amplifier.
condenser used in the conventional distributor are not
This voltage is amplified and used to increase the
used in the magnetic pulse distributor. The magnetic
voltage on the base of the transistor to a value higher
pulse distributor uses a permanent magnet, a timer core,
than that on the emitter. The current flow through the
and a pickup coil. These units produce an alternating
ignition coil primary windings stops.
voltage when the distributor is in operation. This
voltage is transferred to the electrical control section of
With no current flow in the primary ignition
the ignition pulse amplifier.
winding, the magnetic field within the coil collapses
about the windings. The higher voltage induced in the
The ignition pulse amplifier functions as a set of
secondary winding is then impressed upon the
contact points to interrupt the current in the primary
secondary circuit to fire the spark plug. When the
circuit. The voltage developed by the distributor is
voltage reaches a sufficient value to jump the gap
increased by the pulse amplifier and applied to the base
between the electrodes at the plug, a spark is created
of a transistor located in the control section. The control
that ignites the fuel-air mixture in the cylinder of the
transistor acts as a switch and is controlled by the
engine.
voltage supplied to its base circuit. Other electrical
control devices for the transistor are also located in the
The transistor acts as the trigger to interrupt the
control unit.
primary circuit to allow secondary voltage to be
produced. Since the transistor is capable of carrying
For ease of understanding, only the system's basic
more current than the contact points, more secondary
operation will be discussed. Assuming that the ignition
output voltage is available at all engine speeds.
switch is in the run position, current flows through the
emitter-collector of the transistor and the primary
The three basic ignition systems are compared in
winding of the ignition coil. Current flow in the primary
figure 6-46.
winding builds a magnetic field in the primary and
secondary windings, just as it does in the conventional
TROUBLESHOOTING IGNITION SYSTEMS
system.
Before you make any test, conduct a thorough
When the magnetic pulse distributor generates a
visual inspection of the ignition system. Check the
voltage in its winding, the voltage is carries to the
SWITCH
RUN
START
IGNITION
DISTRIBUTOR
COIL
BATTERY
A. CONVENTIONAL SYSTEMS
IGNITION
IGNITION
PULSE
COIL
SWITCH AMPLIFIER
RUN
START
DISTRIBUTOR
BATTERY
B . CONTACT-CONTROLLED
SYSTEM
IGNITION
IGNITION
PULSE
COIL
SWITCH AMPLIFIER
RUN
START
TRANSISTOR
MAGNETIC
ELECTRICAL
PULSE
BATTERY
CONTROL UNITS DISTRIBUTOR
C . TRANSISTOR-CONTROLLED
MAGNETIC
PULSE IGNITION SYSTEM
ASf06046
Figure 6-46.--Comparison of the three basic ignition systems.
6-41