Pontiac FIREBIRD 1972 Service Manual page 754

EMISSION CONTROL SYSTEMS
6D- 1 1
TO VACUUM
ADVANCE ON
TIMED SPARK
ADVANCE HOLE
(MANIFOLD VACUUM)
DISCONNECT AND
PULL OUTWARD ON PLUNGER STEM PLUG DISTRIBUTOP
TO END OF TRAVEL VACUUM HOSE
0
I
THROTTLE LEVER
SHOULD CONTACT
PLUNGER
0
I
TURN SCREW
TO ADJUST
SPECIFICATIONS
L
Fig. 6D-17 C.E.C. Solenoid Adjustment
-
6 Cyl.
Fig. 6D-18 Idle Stop Solenoid (4 Bbl. V-8)
3. With engine shut off, drive new red plastic limiter
caps in place on mixture screws with pin punch.
4. Refer back to step 4 above.
**C.E.C. (250 L-6 only) Valve adjustment is to be made
only after (1) replacement of solenoid, (2) major carbu-
a. With slow idle speed set to specified RPM, manu-
ally extend C.E.C. Valve plunger to contact throt-
tle lever (Fig. 6D-17).
NOTE: C! E. C! valve on 307 V-8 does not have
a deceleration plunger.
b. Adjust plunger length to obtain specified RPM.
EVAPORATION CONTROL SYSTEM
In order to limit gasoline vapor discharge into the atmos-
phere, the following features are incorporated in the fuel
system. The E.C.S. system (Fig. 6D-19) is designed to trap
fuel vapors which normally escape from the fuel tank.
Vapor arrest is accomplished through the use of a char-
coal canister which adsorbs the fuel vapors and stores
them until they can be removed to be burned in the engine.
Removal of vapors from the canister to the engine is ac-
complished by a calibrated purge orifice in the carburetor.
In addition to the carburetor modifications and the canis-
ter, the fuel tank requires a normally non-vented gas cap
and extra vents to a liquidhapor separator (standpipe
design).* The standpipe prevents liquid gasoline from en-
tering the vapor system to the canister. Thus, as vapors are
generated in the fuel tank, they flow through the standpipe
(except station wagon) through a restriction and to the
canister where they are stored. From the canister the va-
pors are routed to the carburetor where they will be
burned during normal combustion. A purge valve is
located on the intake manifold. Its purpose is to prevent
'
purge of the canister to the carburetor until the engine
water temperature reaches approximately 170°F.
*
Station Wagon models do not require the use of a
separator (standpipe design), due to fuel tank design.
retor overhaul, or (3) throttle body has been removed.
(See Section 8).