Ignition Circuit; Description And Operation; Periodic Service; Wiring - Pontiac FIREBIRD 1972 Service Manual

6E-30 1972 PONTIAC SERVICE MANUAL
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BROKEN UPPER INSULATOR
(Firing around shell crimp under load conditions)
Careless removal or installation of spark
Replace with new spark plug.
plug.
BROKEN LOWER INSULATOR
(Firing tip)
Cause is usually carlessness in
regapping by either bending of center
wire to adjust gap, or permitting
gapping tool to exert pressure against
tip of center electrode or insulator,
when bending side electrode to adjust
gap.
Fracture or breakage of lower insulator
may also occur occasionally if engine
has been operated under conditions
causing severe and prolonged detonation
or preignition.
Very seldom occurs but cause is almost
always due to mishandling by applying
excessive torque during installation.
Failure is usually in form of crack in
Vee of thread next to seat gasket or at
groove below hex.
Replace with new spark plug.
Use colder type plug for particular
type of operation.
DAMAGED SHELL
Replace with new spark plug.
DESCRIPTION AND OPERATION
IGNITION CIRCUIT
The ignition circuit consists of the battery, distributor,
ignition coil, spark plugs and primary and secondary wir-
ing. These components are connected electrically as in
Fig. 6E-38.
PERIODIC SERVICE
The distributor and spark plugs are the only components
of the ignition circuit that require periodic service. The
remainder of the ignition circuit requires only periodic
inspection to check operation of units, tightness of electri-
cal connections, and condition of wiring.
WIRING
The low and high tension cables should be examined care-
fully for brittle or cracked insulation and broken strands.
Defective insulation will permit missing or cross firing of
engine. Connections should be clean and tight to reduce
resistance. Poor or high resistance connections in primary
wiring can reduce available voltage for firing spark plugs.
All leads located in either the coil tower or distributor cap
should be checked to make sure they are pressed all the
way down in their inserts. The rubber boots used at these
connections should be tightly in place over connections.
CAUTION: Leadfrom distributormust be con-
nected to coil negative terminal and lead from
ignition switch to coil positive terminal
G N l T l O N
DISTRIBUTOR
COI(L
I
PRIMARV
F ' W I N D I N G
I
!&MAGNETIC
FIELD
CALIBRATED
RESISTMCE
SPARK
PLUG
7
CRANKING
Fig. 6E-38 Ignition Circuit
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Typical