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Fuel,
Emission and Exhaust System
D:08:01
IGNITION VACUUM ADVANCE CONTROL
DESCRIFHON
AND
OPERATION-Fig.
44
The vacuum signal to the distributor advance is not
present during idle and at low engine
temperatures. Distributor advance is cut out at low
temperatures to improve catalytic converter warm-
up.
A thermal vacuum control valve (A), located in
a coolant passage, closes when the coolant
temperature is below 40°C
(104°F)
to prevent
manifold vacuum from reaching the distributor
advance. Above
40°C,
the control valve is open
allowing vacuum to pass to the solenoid valve (B).
The electrically operated solenoid valve
(B)
is
energised whenever the throttle plates are closed.
Energising the solenoid closes the vacuum passage
to the distributor advance, thus eliminating an
over-advanced condition during idle or
deceleration. Solenoid operation is controlled by a
throttle micro-switch (C) which provides an
electrical ground for the solenoid valve when the
throttle plates are closed.
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Vacuum Connection
Spark Advance
Electric Connection
to Micro Switch
Throttle Lever
Fig. 44
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