1987 SUZUKI GRAND VITARA Service Repair Manual

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x-5
5-3

5-l. GENERAL DESCRIPTION
VEHICLE EMISSION CONTROL INFORMATION LABEL
The Vehicle Emission Control Information Label is located under hood. The label contains important
emission specifications and setting procedures, as well as a vacuum hose schematic with emission compo-
nents identified.
When servicing the engine or emission systems, the Vehicle Emission Control Information Label should be
checked for up-to-date information. 1.
Emission control label
2. Hood
EMISSION HOSE ROUTING EGR VACUUM MODULATOR
THERM0 VALVE
\/-
I I
EGR-VALVE-/------
BVSV
Rr,JET
/VACUUM MOTOR
Fig.
5- 1-2 Vehicle emission control information label
5- 4

POSITIVE CRANKCASE VENTILATION (PCV) SYSTEM
(Blow-by gas recycling system)
The blow-by gas in the crankcase flows through the passage in the cylinder block into the cylinder head.
The oil particles are separated from the blow-by gas by the oil separating unit in the cylinder head cover.
The gas is then returned together with the fresh air coming from the air cleaner through the PCV valve
into the intake manifold for recombustion.
When the vacuum in the intake manifold is low (when the opening of the throttle valve is large), the PCV
valve is wide open due to its spring force. Thus a large amount of the blow-by gas is drawn into the intake
manifold.
On the other hand, when the vacuum in the manifold is high, the PCV valve opening is limited due to the
high vacuum. Thus the amount of the blow-by gas drawn into the intake manifold is small.
cz] Fresh air flow
+ Blow-by gas flow
1. Air cleaner case6. PCV (Positive Crankcase Ventilation) valve
2.Air inlet’case7.Cylinderhead cover
3.Carburetor8.Cylinderhead
4.Intake manifold9.Cylinderblock
5.3-way joint10.Oil pan
Fig. 5-l-3 PCVsystemoperation
5-5

THERMOSTATICALLY CONTROLLED AIR CLEANER (TCAC) SYSTEM
This system helps to improve fuel vaporization by controlling the temperature of the intake air almost at
a constant level automatically regardless of driving conditions and outside temperature, to distribute the
mixture to each cylinder evenly and to stabilize the air/fuel mixture ratio.
It consists of the therm0 sensor (therm0 valve) and the Air Control Actuator (ACA). The therm0 sensor
located in the air cleaner case senses the temperature of the intake air and controls the vacuum line by
opening and closing its passage to the ACA. According to this opening and closing operation, the vacuum
in the intake manifold actuates the damper through the diaphragm in the ACA. For the warm air, the air
is warmed up in the exhaust manifold cover and for the cold air, the outside air is drawn through the
fresh air passage and both enter the air cleaner.
“A” Warm air delivery mode
6“B” Regulating mode
“C” Cold air delivery mode
1. ACA (Air Control Actuator)
2. Damper3. Warm air duct
4. Therm0 sensor (valve)5.’ Air cleaner case66. Air cleaner inlet case
7. Carburetor8. Intake manifold9. Check valve10. Diaphragm11. Warm air
12. Cold air
13. Orange
--

System Operation
When engine is started in cold weather, the therm0 valve is closed because the temperature of the intake
air in the air cleaner is low. Therefore, the vacuum is transmitted to the ACA diaphragm, which then
pulls up the damper linked to the diaphragm to open the warm air duct fully. As the engine is warmed up,
the temperature of the intake air coming into the air cleaner from the warm air duct rises and the therm0
valve starts opening. As a result, the vacuum transmitted to the ACA diaphragm decreases, and the damper
pushed down by the spring force lessens the warm air duct opening. In this state, warm air and cold air
are mixed together and enters the air cleaner.
When the engine is operating at high rpm and under high load condition, the temperature of the air
coming from the warm air duct rises very high, causing the therm0 valve opening to become even larger
and the damper opening smaller. That is, the amount of the warm air coming from the warm air hose
decreases and the cold air amount increases.
In this way, this system serves to maintain the temperature of the intake air going into the carburetor
almost at a constant level.
5-6
FIG. 5-1-4 TCAC system operation

EVAPORATIVE EMISSION CONTROL SYSTEM
An evaporative emission control system is used to prevent emission of fuel vapors from the vehicle fuel
system.
The system allows evaporating fuel vapors to be stored, when the engine is not running.
This is accomplished by venting the fuel tank and carburetor float chamber through a vapor storage
canister containing activated charcoal.
The major system components are vapor storage canister, vent solenoid, and liquid vapor separator.
The fuel vapor from the fuel tank is led into the canister and stored there when the engine is not running.
The fuel vapor from the carburetor float chamber is also stored in the canister when the ignition switch is
“OFF”.
When engine runs, the fuel vapor stored in the canister is drawn into the carburetor together with fresh
air.
For vent solenoid valve operation, refer to item of “BOWL VENTILATION SYSTEM.”
2
1 Fuel vapor flow
+llal Fresh air flow
1. Intake manifold2. Vapor storage canister
3. Liquid vapor separator4. Fuel tank
5. Carburetor6. Vent solenoid valve
Fig. 5- l-5 Evaporative emission con trot sys tern
5-7

HOT IDLE COMPENSATOR (HIC)
HIC attached to the air intake case serves to provide the optimum air/fuel mixture during hot idle so as to
ensure stable idle speed.
HIC has a bimetal which warps as the heat transferred to it rises higher than about 55°C (131” F). Caused
by this, the valve in HIC starts to open and it reaches to the full open state at about 70°C (158” F).
While the engine at idle, the throttle valve is closed and the vacuum in the intake manifold stays high. As
the HIC valve opens in this state, the air from the air cleaner is drawn through the HIC valve into the
intake manifold to prevent the air/fuel mixture getting richer during hot idle, thus maintaining a stable
idle speed.
1. Air cleaner
r‘i/ ,
4. HIC
2. Air intake case5. Bi-metal
3. Intake manifold6. H IC valve
Fig. 5- l-6 Hot idle; compensator
5-8

DECELERATION MIXTURE CONTROL SYSTEM
This system consists of a MCV (Mixture Control Valve), jet and vacuum hoses.
This system is designed to introduce fresh air into the intake manifold to reduce generation of excessive
HC and CO emission caused by temporary rich air-fuel ratio while rapid deceleration.
The MCV has a pressure balancing orifice and check valve on its diaphragm, and closes when manifold
vacuum is constant. As manifold vacuum increases according to rapid deceleration, manifold vacuum
applies to MCV chamber “B” through jet, the MCV opens and introduces fresh air into the intake mani-
fold. When manifold vacuum becomes constant, pressure difference between two sectioned chambers “A”
and “B” gradually diminishes through pressure balancing orifice, then the MCV closes.
1.Carburetor7. Valve
2. Intake manifold8. Filter3.MCV9. Jet (Colorless)
4.Chamber “A”9-1. Gray side
5.Orifice10. Diaphragm
8.Chamber “B”11. Check valve
Fresh airc=l
1Vacuum
Fig. 5-l-7Deceleration mixture control system
5-9