Chevrolet BEAUVILLE SPORTVAN G10 SERIES, Руководство по обслуживанию

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EMISSION C O N TR O L SYSTEM 6T-2
dieseling tendencies by allow ing th e th ro ttle valve to close
b eyond th e norm al idle positio n w hen the ignition is turn ed
off.
SYSTEM TH E O R Y
The TCS system co m p o n en ts are shown in their norm al at
rest position w ith th e engine o ff and cold (Fig. 6T-1). The
tem perature sw itch p o in ts are closed, m aking c o n tac t w ith the
cold term inal; the tim e relay p o in ts are closed, transm ission
sw itch p o in ts are op en ; CEC solenoid is de-energized, plunger
retracted an d blocking d istrib u to r vacuum advance and
opening d istrib u to r vacuum advance u n it to atm osphere; idle
sto p solenoid is de-energized w ith plunger retracted.
When th e ignition sw itch is tu rn ed on th e idle stop solenoid
is energized, extending th e plunger to c o n tac t th e th ro ttle
lever. A circuit is co m p leted fro m th e ignition sw itch th rough
the CEC solenoid a n d th rough th e tem p eratu re sw itch cold
term inal to ground. A t th e same tim e a n o th e r circuit is
energized — this is fro m th e ignition sw itch th rough the tim e
relay coil and to ground, also as long as th e relay p o in ts are
closed it provides a p ath to ground for th e CEC solenoid (Fig.
6T-2). With either one or b o th o f th e above circuits com plete,
the CEC solenoid is energized; p erm itting vacuum advance to
d istrib u to r and, additionally, th e CEC solenoid plunger ex ­
tends, contacting th e th ro ttle lever to provide deceleration
co n tro l at a preset value.
In low gear operatio n , w ith engine tem p eratu re above 82
degrees, th e tem p eratu re switch cold override p o ints open
(Fig. 6T-3). I f 20 seconds have elapsed the tim e relay points
are open also. This breaks th e circuit(s) de-energizing the CEC
solenoid, allow ing the plunger to block vacuum and open
advance u n it to atm osphere — deceleration co n tro l is no
longer effective, leaving th ro ttle co n tro l to be perform ed by
the idle sto p solenoid.
When the transm ission is shifted in to high forw ard gear, the
transm ission sw itch p oints are closed by shift action or by oil
pressure as applicable (Fig. 6T-4). This com pletes th e circuit
from the ignition switch th rough the CEC solenoid and
th rough the closed transm ission sw itch p o in ts to ground. The
CEC solenoid plunger is ex ten d ed to provide deceleration
co n tro l and to open the vacuum p o rt to the advance u n it.
(Cold Override & T im e Relay Energized)
Fig. 6 T -4 —L-6 TC S System (High Gear Operation)
C H E V Y V A N S H O P M A N U A L