sensor OPEL GT-R 1973 Service Manual

6F- 601973 OPEL SERVICE MANUAL
EMISSION CONTROL SYSTEMS
ALL MODELS
CONTENTS
Subject
DESCRIPTION AND OPERATION:
DescriptionandOperationofO.E.C.S.. . . . . . . . . . . . . . . . . . . . . . . .Exhaust
GasRecirculationSystem. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .DIAGNOSIS:
Testing Therm0 Air Cleaner Operation
. . . . . . . . . . . . . . . . . . . . . .Exhaust
GasRecirculationSystem. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .MAINTENANCE AND ADJUSTMENTS:
Exhaust GAS Recirculation System
. . . . . . . . . . . . . . . . . . . . . . . . . . . .MAJOR REPAIR:
Removal and Replacement of O.E.C.S. Units
. . . . . . . . . .SPECIFICATIONS:
Opel Emission Control System Specifications
. . . . . . . .Page No.
6F-60
6F-62
6F-62
6F-636F-636F-636F-64
DESCRIPTION AND OPERATION
OPEL EMISSION CONTROL SYSTEM (O.E.C.S.)All 1973 cars must be capable of passing certain tests
which measure the quantity of unburned impurities
in the exhaust system. Federal law places a limit on
the hydrocarbon and carbon monoxide emissions
from the exhaust system. The purpose of this law is
to keep the atmosphere cleaner, particularly in popu-
lous areas where these impurities add to the smog
problem. Basically, excessive exhaust emissions are
caused by incomplete combustion of the air-fuel mix-
ture in the cylinders.
The basic components of the OECS on the 1.9 liter
engines are (1) leaned out carburetion, (2) heated air
(except GT), and (3) tuned spark timing.
(1) The carburetor idle system is leaned out and
special features are incorporated into the carburetors
to make possible additional idle mixture adjustments
over and above those manufactured into the carbu-
retors.
(2) The heated air package consists of a heat stove,
a corrugated paper heated air pipe, and an air cleanercontaining a temperature controlled door operated
by vacuum through a temperature sensor. See Figure6F-1.The heat stove is a sheet metal cover, shaped to and
bolted onto the exhaust manifold. Air drawn in along
Figure
6F-1 Heated Air System Installed

EMISSION CONTROL SYSTEMS6F- 61I
1.HEAT STOVE
2.CONNECTING HOSE.
3.VACUUM DIAPHRAGM
4.VALVE (El-METAL SPRING)
5.VACUUM HOSES
6.AIR CLEANER HOUSING
7.CARBURETOR
BF-2
Figure 6F-2 Heated Air Systemthe lower edge of the stove passes across the manifold
surface, picking up heat. The heated air is drawn out
from the upper end of the manifold, through the
heated air pipe into the snorkel of the air cleaner. See
Figure
6F-2.The temperature control air cleaner is designed to
mix this heated air with cold air from under the hood
so that carburetor inlet air temperature averages
about 115 degrees. This mixing is done by an air door
located in the air cleaner snorkel. Most of the time,
the door will be partially open, as required, to control
the temperature. When the underhood temperature
reaches about 135 degrees, the door will close tight,
not allowing any more warm air from the mainifold
to enter the snorkel of the air cleaner. Obviously, if
underhood temperatures rise above 135 degrees, theair cleaner will no longer be able to control tempera-ture and the inlet air temperature will rise with
un-derhood temperature.
The temperature door is moved by a diaphragm type
vacuum motor. When there is no vacuum present in
the motor, the diaphragm spring forces the door
closed. Whenever the engine is running, the amount
of vacuum present in the vacuum motor depends on
the temperature sensor in the air cleaner which is
located in the vacuum line between the intake mani-
fold and the vacuum motor. In the sensor, a bi-metal
temperature sensing spring starts to open a valve to
bleed more air into the vacuum line whenever the
temperature in the air cleaner rises above about 115
degrees. Whenever the temperature falls below about
115 degrees, the sensing spring starts to close the air

6F. 62 1973 OPEL SERVICE MANUAL
bleed into the vacuum line, allowing more manifold
vacuum to reach the vacuum motor. Whenever there
is nine inches or more of vacuum in the vacuum
motor, the diaphragm spring is compressed, the door
is opened.
When the engine is not running, the diaphragm
spring will always hold the door closed. However,
when the engine is running, the position of the door
depends on the air temperature in the air cleaner.
When starting a cold engine (air cleaner temperature
under 85 degrees), the air door will open immedi-
ately. This is because the air bleed valve in the sensor
is closed so that full manifold vacuum, is applied in
the vacuum motor. As soon as the air cleaner starts
receiving hot air from the heat stove, the sensor will
cause the air door to close partially, mixing cold air
with the hot air as necessary to regulate air cleaner
temperature within 20 degrees of the ideal 115 de-
grees air inlet temperature.
If underhood air temperature rises to 135 degrees,
the air bleed valve in the sensor will be wide open so
that vacuum to the vacuum motor approaches zero.
The diaphragm spring in the vacuum motor will hold
the air door closed tightly. If underhood temperature
rises above 135 degrees, carburetor inlet air tempera-
ture will also rise above 135 degrees.
While air cleaner temperature is being regulated, ac-
celerating the engine hard will cause the vacuum
level in the intake manifold and in the vacuum motor
to drop. Whenever vacuum drops below 5 inches, the
diaphragm spring will close the air
door in order to
get the
maxumum outside air flow required for max-
imum acceleration.
The carburetor is set by the manufacturer for
800-
850 RPM (automatic transmission) or 850-900 RPM
(manual transmission) and 1.5 to 2.5 percent CO.
Figure 6F-3 E.G.R. System
EXHAUST GAS RECIRCULATION SYSTEM
All 1973 Opel 1900’s, Manta’s and GT’s are
equipped with an exhaust gas recirculation (E.G.R.)
system. See Figure
6F-3.
The E.G.R. system consists of a pipe connected to
the center of the front exhaust pipe, an E.G.R. valve,
a short pipe from the valve to the intake manifold
and a short vacuum hose from the E.G.R. valve to
the base of the carburetor. See Figure
6F-4.
The system does not receive sufficient vacuum at idle
to operate, but will operate during acceleration and
part throttle providing sufficient intake manifold
vacuum is present.
Figure 6F-4 E.G.R. Valve Location
DIAGNOSIS
TESTING THERMO AIR CLEANER OPERATION
Since failure of the therm0 air cleaner will generally
result in the snorkel air door staying open, failure
will probably go unnoticed in warm or hot weather.
In cold weather, however, owners will complain of
leaness, hesitation, sag, surge, or stalling. When any
type of lean operation complaint is received, always
test the thermo air cleaner for
proper functioning
before doing any work on the carburetor.
Always perform checks in the same order as listed
below.
Vacuum Motor Check
1. Check all hoses for proper hookup. Check for
kinked, plugged, or damaged hoses.

EMISSION CONTROL SYSTEMS6F- 63
2. With the engine “OFF”, observe damper doorposition through snorkel opening. If position of snor-kel makes observation difficult “se the aid of a mir-
ror. At this point damper door should be in such a
position that the heat stove passage is covered (snor-
kel passage open). If not, check for binds in linkage.3. Apply at least nine in. Hg. of vacuum to dia-
phragm assembly through hose disconnected at sen-
sor “nit. This can be done by mouth. Damper door
should completely close snorkel passage whenvacuum is applied. If not, check to see if linkage is
hooked up correctly and for a vacuum leak.
4. With vacuum applied, bend or clamp hose to trapvacuum in diaphragm assembly. Damper door
should remain in position (closed snorkel passage). Ifit does not, there is a vacuum leak in diaphragm
assembly. Replace diaphragm assembly.
Sensor Check
Quick Check of System:
1. Start test with engine cold, air cleaner at a temper-ature below 85 degrees. If the engine has been in
recent “se, allow it to cool.
2. Observe the air door before starting the engine: it
should be closed.3. Start the engine and allow it to idle. Immediately
after starting the engine, the air door should open.
4. As the engine warms up, the air door should start
to close, and the air cleaner should become warm tothe hand.
5. The system is operating normally as described
above. If the air cleaner fails to operate as above or
if correct operation of the air cleaner is still in doubt,
proceed to the thermometer check.
Thermometer Check of Sensor:1. Start test with air cleaner temperature below 85
degrees. IF ENGINE HAS BEEN RUN RE-
CENTLY, ALLOW IT TO COOL DOWN. Whileengine is cooling, remove air cleaner cover and in-
stall a temperature gage such as J- 22973 as close as
possible to
se&r. Keinstall air cleaner cover. Let car
stand idle for
l/2 hour or more before proceeding to
step 2.2. Start the engine. Air door should open immedi-
ately if engine is cool enough. When air door starts
to close (in a few minutes), remove air cleaner cover
and read temperature gage. It must
read 115 degreesplus or minus 20 degrees.
3. If air door does not start to close at temperatureindicated, temperature sensor is defective and must
be replaced.
EXHAUST GAS RECIRCULATION SYSTEM
TestingThe exhaust gas recirculation valve is to be checked
at 12,000 mile intervals “sing the following proce-
dure:1. With engine at operating temperature, connect a
tachometer to engine and note R.P.M. at idle.
2. Disconnect vacuum hose at the intake manifold
that goes to the air cleaner.
3. Disconnect vacuum hose for exhaust gas recircula-tion valve from the throttle valve and connect it to
the intake manifold where vacuum hose to air
cleaner was connected.4. Engine speed should decrease between
100-240R.P.M. from previously noted R.P.M.
5. If the R.P.M. decrease is less than 100 R.P.M., theexhaust gas recirculation valve and fitting going into
the intake manifold must be removed, cleaned, and’
reinstalled.
MAINTENANCE AND ADJUSTMENTS
EXHAUST GAS RECIRCULATION SYSTEM
CleaningClean the exhaust gas recirculation valve and fitting
with a piece of stiff wire removing all exhaust depos-
its.
CAUTION:Do not soak in solvent. After
r.einstafIing the valve and fitting, check op
eration as outlined under “Testing”. If
vahe does not operate properly after a
thorough cleaning, replace it.
MAJOR REPAIR
REMOVAL AND REPLACEMENT OECS UNITSThe damper door is not serviceable. The air cleaner
assembly must be replaced if the damper door is
defective.
R And R Vacuum Motor
1. Remove vacuum
motor retainer spring. See Figure
6F-5.

6F. 641973 OPEL SERVICE MANUAL
Figure 6F-5 Replacing Vacuum Motor Assembly
2. Lift vacuum motor, cocking it to one side to un-
hook motor linkage at the control door.
3. Install in reverse sequence.
R And R Air Cleaner Sensor
1. Remove sensor retaining clips by prying. See Fig-
ure
6F-6.2. Pull vacuum hoses from sensor.
3. Note carefully the installed position of the sensor
SPECIFICATIONS
EMISSION CONTROL SYSTEM SPECIFICATIONSFigure
6F-6 Replacing Sensor Assembly
so that you can install new sensor in same position.
Then remove sensor.
4. Install sensor and gasket assembly in air cleaner
in same position as noted in Step 3. This is to elemi-“ate the possibility of interference with the air filter
element. See Figure
6F-4.5. Install sensor retaining clip. Meanwhile support-
ing sensor around the outside rim to prevent damage
to the temperature sensing spring.
6. Reinstall vacuum hoses.
Carburetor Inlet Air Regulated Temperature
..........................................................115” k 20
Idle Mixture Setting (Lean From Best Idle)
..............................................................50 RPMTherm0 Vacuum Switch Operating Temperature
............................................................220Engine Thermostat Operating Temperature
......................................................................189