Bronco L6-300 4.9L VIN Y 1-bbl (1983)
Dual Diaphragm Assembly
DUAL DIAPHRAGM ASSEMBLY
The dual diaphragm assembly, Fig. 12, obtains spark advance in the same manner as the single diaphragm assembly. In this case vacuum applied to the
vacuum advance port causes the advance diaphragm and attached rod to move, otherwise the action is the same. Spark retard is done by applying vacuum
to the vacuum retard port. This causes the retard diaphragm to move, compressing the retard spring, which controls the rate of spark retard. Compressing
the retard spring allows the diaphragm rod stop to move due to the force applied by the advance spring pushing against it by means of the diaphragm rod.
The result is the diaphragm rod moves causing the attached stator assembly to change position with respect to the armature. In this instance the direction
of the stator assembly movement is opposite that occurring during vacuum advance, resulting in spark retard.
NOTE: Any vacuum applied to the advance port overrides any spark retard caused by vacuum being applied to the retard port.
