engine OPEL GT-R 1973 Owners Manual

CARBURETOR AND THROTTLE LINKAGE6E- 63
4. Adjust engine idle speed and mixture
CAUTION: : Make sure choke valve opensfully before starting idle adjustment.
THROTTLE LINKAGE REMOVAL
Removal
Opel 1900 and Manta Series1. Remove control wire from bracket and unhook it
from segmental disc. See Figure
6E-16.2. In passenger compartment, unhook wire with ball
and plastic bushing from accelerator pedal lever. See
arrow in Figure 6E- 18.
Figure 6E.18 Unhook Wire in Passenger
Compartment3. In engine compartment, pull bowden control wire
out of bracket on dash panel.
If bowden control wire is kinked or damaged in any
way, it must be replaced.
1. Feed ball and plastic bushing from engine com-
partment through opening in dash panel and hook in
accelerator pedal lever. See Figure
6E-19.2. Lightly pull wire core so that the plastic bushing
slips into bore of accelerator pedal lever.
3. Hook bowden control wire in segmental disc and
attach control wire to bracket.Figure
6E-19 Installing Ball and Plastic Bushing
4. Adjust control wire.
OVERHAUL CARBURETORDisassembly
1. Remove outer nut from end of throttle lever to
choke link. See Figure
6E-20.
Figure 6E-20 Removing Choke Link
2. Pry off vacuum case connecting lever. See Figure
6E-2 1.3. Unscrew carburetor cover.
4. Screw float needle valve out of carburetor cover
and take off copper seal ring.

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

TUNE-UP
ALL MODELS
CONTENTS
Subject
DESCRIPTION AND OPERATION:
Purpose of a Tune-Up. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . , . . . .DIAGNOSIS: (Not Applicable)
MAINTENANCE AND ADJUSTMENTS:
EngineTune-UpMechanicalOperations. . . . . . . . . . . . . . . . . . . .
EngineTune-UpInstrumentChecks. . . . . . . . . . . . . . . . . . . . . . . . . . . .MAJOR REPAIR: (Not Applicable)
SPECIFICATIONS:
Tune-Uo Soecifications and Adjustments
. . . . . . . . . . . . . . . .Page No.6G-65
6G-6566-6766-68
DESCRIPTION AND OPERATION
PURPOSE OF TUNE-UP
The purpose of an engine tune-up is to restore powerand performance that may have been lost through,
loss of adjustment, wear, corrosion, or deterioration
of one or more parts or units. In the normal operat-
ion of an engine, these changes take place gradually
at quite a number of points so that it is seldom advis-able to attempt an improvement in performance by
correcting one or two items only. Time will be savedand more lasting results will be assured by following
a definite and thorough procedure of analysis and
correction of all items affecting power and perform-
ance. Because of Federal laws, limiting exhaust emis-sions, it is even more important that the engines
tune-up is done accurately, using the specifications
listed and the tune-up sticker found in each engine
compartment.
Economical, trouble free operation can better be as-sured if a complete tune-up is performed at first 4
months or
6,ooO miles of operation - then at 12
month or 12,000 mile intervals.
The parts or units which affect power and perform-
ance may be divided, into three groups (1) compres-sion, (2) ignition and (3) carburetion. The tune-up
procedure should cover these groups in the order
given. While the items affecting compression and
ignition may be handled according to individual
preference, correction of items in the carburetiongroup should not be attemplcu
ulllll all items in
compression and ignition have been satisfactorily
corrected.
MAINTENANCE AND ADJUSTMENTS
ENGINE TUNE-UP OPERATIONS
CompressionTo make sure hydrocarbon and carbon monoxide
emissions will be within limits, it is very important
that the adjustments be followed exactly.
The suggested procedure for engine tune-up is as
follows:1. Remove all spark plugs.
2. Position throttle and choke valve in full open posi-tion.
3. Connect jumper wire between distributor terminalof coil and ground on engine to avoid high tension
sparking while cranking engine.
4. Hook up starter remote control cable and turn
ignition switch to “on” position.
5. Firmly insert compression gage in spark plug port.Crank engine to obtain highest possible reading.

6G- 661973 OPEL SERVICE MANUAL
6. Check compression of each cylinder. Repeat
compression check and record highest reading ob-
tained on each cylinder during the two pressurechecks.The recorded compression pressures are to be con-
sidered normal if the lowest reading cylinder is more
than 75 percent of the highest reading cylinder. See
the following example and the “Compression Pres-
sure Limit Chart.” See Figure
6G-2.Seventy-five percent of 140 (highest) is 105. Thus,
cylinder No. 4 is less than 75 percent of No. 3. This
condition, accompanied by low speed missing, indi-
cates an improperly seated valve or worn or broken
piston ring. See Figure 6G-1.
23
I
SO-1Figure 6G-1 Example of Compression Check
7. If one or more cylinders read low, inject about a
tablespoon of engine oil on top of pistons in low
reading cylinders through spark plug port. Repeat
compression check on these cylinders.
a: If compression improves considerably, rings are
lV0*tl.b. If compression does not improve, valves are stick-
ing or seating poorly.
c. If two adjacent cylinders indicate low compression
and injecting oil does not increase compression, the
cause may be the head gasket leaking between the
cylinders. Engine coolant and/or oil in cylinders
could result from this defect.
Compression Pressure Limit ChartThis chart may be used when checking cylinder com-
pression pressures. It has been calculated so that the
lowest reading number is 75 percent of the highest
reading number. See Figure 6G-2.
EXAMPLE: After checking the compression pressures
in all cylinders, it was found that the highest pressure
obtained was 182 psi The lowest pressure reading
was 145psi.
By locating 182 in the maximum col-
umn, it is seen that the minimum allowable pressure
r-.__MAXIMUM
PRESSURE
POIJNWW. INCH
--
134
136
138
140
142
146148
150
152
154
156
158160lb2
164166168170172
174
176
178
180182184
186MINIMUM
PRESSURE
POUNDS/
SQ. INCHHAXIMUM
‘RESSURE
‘OUNWiQ. INCHMINIMUM
PRESSURE“OUNWX?. INCH
101188I41I02190142104192144105194145107196147II0198148Ill200150
113202151
114204153
115206154
117208156118210157120212158
121214160123216162
124218163
126220165127222166129224168131226169132228171133230172
135232174136234175138236177140238178
Figire 6G.2 Compression Pressure Limit Chart
is 136psi. Since the lowest reading obtained was 145
psi,
the car is within limits and the compression is
considered satisfactory.
Spark Plugs1. Inspect, clean and regap or replace spark plugs as
required. Correct gap is
,030.2. Install spark plugs. Tighten to 30 lb.ft.
Secondary Ignition System1. Inspect ignition cables for broken, swollen or
deteriorated insulation.
2. Check terminal ends and condition of rubber
boots. Replace as required.
3. Inspect the condition of the distributor cap and
rotor.
4. Clean the ignition coil and inspect for cracks or
carbon paths which could cause high voltage leak-
age.
Distributor Contact Points1. Inspect distributor contact points and replace or
adjust as necessary
(.016 gap).

2. If inspection of contact points indicates excessive
burning, pitting or wear, check condenser and re-
place if necessary.
3. Inspect all connections and wires in the primary
ignition circuit. Correct any abnormal conditions
found.Carburetor1. Clean fuel strainer in fuel pump. To prevent fuel
leakage in pump, disconnect “IN” line from pump
and raise end above fuel level. The in-line fuel filter
should be replaced every 12,000 miles or every 12
months.
2. Check for freedom of choke valve operation and
clean shaft if necessary, with suitable solvent.
3. Inspect throttle cable or linkage bracket and re-
turn spring for wear. With helper depressing acceler-
ator pedal to floor, check for wide open throttle.
Adjust accelerator pedal height so wide open throttle
is obtained when pedal is within
l/2 inch from floor.
Lubricate linkage pivot points with engine oil.
Air CleanerCheck paper element every 6,000 miles and replace
every
24,ooO miles. If a vehicle is operated in dusty
territory, check condition of air cleaner element
more frequently and replace if necessary.
Fan Belt1. Inspect belt for wear, cracks or frayed points.
Replace and/or adjust as necessary. Specified ten-
sion for belt using Gauge J-23600 is 45 lbs.
Cooling System1. Inspect the radiator, water pump, cylinder head
areas and all radiator and heater hose connections
for evidence of engine coolant leaks.
2. Inspect all hoses for deterioration from gas and oil
contact. Correct as required.
Inspection should be made with engine operating at
normal temperature, cooling system completely
filled, temperature control lever fully open and nor-
mal pressure in the system. Normal pressure should
be 13.2 to 15.2 psi.
Engine Lubrication SystemInspect engine for evidence of oil leakage. Correctany abnormal condition with sealastic or new seals
and gaskets.
Battery
1. Inspect battery, battery mount and cables and
check electrolyte level. Proper level should be just
above the cell plates.
CAUTION:Do not over fill.
2. Determine the serviceability of the battery by ap-
plying the 421 Battery Test.
Positive Crankcase VentilationClean crankcase ventilator metered orifice in the in-
take manifold fitting every 6,000 miles. Also all hoses
and fittings should be inspected, cleaned and re-
placed, if necessary.
To clean, remove rubber hose from metered orifice
and apply air pressure to orifice to remove any for-
eign particles that may be trapped.
Valve Lifter AdjustmentRefer to Engine Mechanical and Mounts section for
valve lifter adjustment procedure.
Engine Tune-Up Instrument ChecksThe following instrument checks and adjustments
serve as a final check on engine condition. These
checks may discover some new problems that may
not have been obvious before. The engine is also
given its final adjustments that will assure maximum
performance, reliability, and proper emission con-
trol.
Refer to Electrical Group for checking procedures of
the following:
Cranking Voltage Check
Ignition Timing
Distributor Advance
Ignition Output
Secondary Resistance
Current Output and Voltage Setting
Idle Speed and Mixture AdjustmentsRefer to carburetor section.

6G- 68 1973 OPEL SERVICE MANUAL
SPECIFICATIONS
TUNE-UP SPECIFICATIONS AND ADJUSTMENTS
Voltage Regulator
Voltage Regulator Setting in Volts at2500 Engine RPM. . . . . . . . . . . . . . . . . . . . . .14+.5
Ignition Coil
Ignition Coil Current Draw, Amperes at 12.5 Volts
Engine Stopped
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . \
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . \
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . \
. . . . . .3.8
EngineIdling. . . . . . . . . . . . . . . . . .._.....................................................................\
........................... 2.3
Total Advance (Centrifugal and Vacuum), Engine Degrees at 3600 Engine \
RPM......29-38
Centrifugal Advance, Engine Degrees and RPM
Start Advance, atRPM
........................................................................\
................ 1000-1200
Medium Advance, Degrees at RPM..............................................................7.5-15 at 1400
Maximum Advance, Degrees at RPM
..........................................................28-32 at 3600
Vacuum Advance, Engine Degrees and In. of Vacuum Start Advance..
........................................................................\
.................-5at2.9-4.1 In.
Maximum Advance..........................................................................\
........1-5at4.5-5.0In.
Vacuum Retard, Engine Degrees at Closed Throttle............................................................-5
Condenser Capacity in
MicroFarads........................................................................\
.......23-.32
Breaker Spring Tension in Ounces........................................................................\
......14 to 19
Breaker Point Gap in Inches
........................................................................\
......................,016
Dwell AngleinEngine Degrees........................................................................\
.......... 50+3
Firing
Order........................................................................\
............................................l-3-4-2
Spark Plug or Coil Cable,Max.Resistance in Ohms
..................................................
10,000
Spark Plugs
Make and Model Production........................................................................\
............AC42FS
Make andModel
-Replacement........................................................................\
..........AC42FS
If carbon fouling occurs, use
........................................................................\
............AC43FS
Spark Plug Torque in
Lb.Ft.........................................................................\
.........................30
Spark Plug Gap in Inches........................................................................\
..........................,030
Valve Lifter Adjustment
One full turn (clockwise) after zero clearance is obtained - refer to Valve Adjustment
Procedure
Ignition Timing
Align timing marks with distributor retard hose disconnected and plugged\