1973 OPEL 1900 rod

CARBURETOR AND THROTTLE LINKAGE65 47
Figure 6E.3 Secondary Vacuum Diaphragm
Figure
6E-4 Automatic Choke System
Figure
6E-5 Idle Systemin a richer mixture. When the throttle valve is
opened, fuel is also drawn from the upper ports,
providing a good transfer from the idle system to the
main metering jet system. See Figure
6E-5.Main Metering Jet System
During high-speed operation, fuel is drawn from the
float chamber through the main metering jet (Figure6E-2) into the emulsion tube bore. The emulsion
tube, which is provided with transverse bores, is in-
serted in the emulsion tube bore. Vacuum in the
primary venturi (Figure 6E-2) draws fuel from the
main nozzle. As the vacuum increases, the tendency
is to draw too much fuel from the main nozzle, mak-
ing the mixture too rich. To compensate for this
tendency, the fuel level drops in the emulsion tube
bore and more emulsion tube transverse bores are
exposed. Air from the high speed air jet (Figure6E-2) enters the emulsion tube through these trans-
verse bores and mixes with the fuel. The more the
fuel level drops, the more the transfer bores are ex-
posed. This causes the air-fuel ratio to remain con-
stant over the whole engine speed range. See Figure
6E-6.Figure
6E-6 High Speed System
The secondary valve diaphragm is operated by
vacuum taken from the mixing chamber of the pri-
mary barrel on the Opel 1900 and Manta only. With
the primary throttle valve almost open and with en-
gine speed at approximately half of the maximum
engine RPM, vacuum increases to such an extent
that the secondary throttle valve starts opening from
vacuum applied in the vacuum diaphragm case act-
ing through a connecting rod and throttle valve
lever. See Figure
6E-3.
Primary to Secondary Transfer SystemIn order to have a smooth engagement of the
second-

6~. 46,1973 OPEL SERVICE MANUAL
ary barrel, it is provided with g transfer system.
When the secondary throttle valve starts to open,
two‘ports (which are normally just above the closed
valve) are uncovered, causing fuel to feed into the
secondary bore just before the secondary nozzle
starts feeding. This provides for an additional enrich-
ment of the air-fuel mixture at the beginning of full
throttle operation. See Figure
6E-7.
nInFlFigure
6E-7 Primary to Secondary Transfer System
Full Thrdttle Enrichment SystemIf the secondary throttle valve is fully opened, the
vacuum in the throttle valve area is reduced so that
the transfer ports (mentioned above) stop feeding.
However, the vacuum increases greatly in the sec-
ondary venturi area. An enrichment tube which pro-
trudes into the primary venturi area, feeds fuel
continuously during full throttle operation. See Fig-
ure
6E-2.
Acceleration SystemWhenever the throttle is closing, the suction stroke
of the diaphragm pump causes fuel to flow from the
float chamber through the inlet ball valve into the
pump chamber. When the throttle valve is opened
the diaphragm is moved inward by the pump con-
necting rod and the pump lever. Fuel is injected into
the primary bore through the injector tube. The
amount of fuel is determined by the pump stroke.
The inlet ball valve in the pump chamber prevents
fuel from flowing back into the float chamber during
the pressure stroke of the pump. The outlet ball valve
prevents air from being drawn into the injector tube
during the suction stroke of the pump. See Figure6E- 8.
Float Bowl VentilationWhile driving, the float bowl is ventilated from insideFigure
6E-8 Acceleration System
the carburetor. That is, the float bowl is connected
through the vent valve with the area under the air
cleaner.
When the engine is idling or off, the ventilation from
inside is cut off and ventilation from the charcoal
canister is cut in. The upper spring now seats the
valve on the upper seat. See Figure
6E-9.
-6E-9
Figure
6E-9 Float Bowl VentilationThe advantage of an inside vent while driving is that
air cleaner restriction does not enrichen the air fuel
mixture. The purpose of the charcoal canister vent
while idling or after shutting-off a hot engine, is to
prevent excess fuel vapors from entering the intakemanifold and outside air. Excess fuel vapors may
cause an idling engine to stall, or may make it dif-
ficult to restart a hot engine.

CARBURETOR AND THROTTLE LINKAGE6E- 51
water, adjust the throttle stop screw to read 6 inches
of water (3 inches down and 3 inches up).
4. Disconnect manometer and reconnect the vacuum
advance hose.
5. Adjust idle air speed screw and mixture screw to
obtain maximum idle at 850 to 900 R.P.M. (auto-
matic transmission) or 900 to 950 R.P.M. (manual
transmission).
6. Make final adjustment by turning idle mixture
screw in to reduce idle speed 50 R.P.M.
7. Install red plastic caps over the air speed screw
and idle mixture screw. Replace plastic cap over the
throttle valve stop screw and secure in place with
Loctite.
Fast Idle Speed Adjustment
1. Remove air cleaner cover.
2. With engine off, open the throttle halfway and
close the choke valve, release the throttle, then re-
lease the choke.
3. Start engine without moving the throttle. Adjust
to 3200 to 3300 R.P.M. using 2 nuts on fast idle rod.
See Figures 6E-13 and
6E-14.Figure
6E-13 Decreasing Fast Idle Speed
CARBURETOR LINKAGE ADJUSTMENT
GT Series1. Remove air cleaner.
2. Have helper depress accelerator pedal to floor and
check to see if wide open throttle is reached at carbu-
retor.
3. If adjustment is necessary, proceed as follows:
6E-14Figure
6E-14 Increasing Fast Idle Speed
(a) Unhook accelerator pedal return spring.
(b) Remove lock spring at upper end of vertical con-
trol rod and detach rod.
(c) Lengthen or shorten control rod so that wide
open throttle is obtained at the carburetor when ac-
celerator pedal is
l/4” - l/2” from floor mat.
(d) Reinstall rod, lock spring and pedal return
spring.
Opel 19W and Manta SeriesThe carburetor bowden control wire is properly ad-
justed if, with correctly-adjusted engine idle speed,
engine at operating temperature and accelerator
pedal at an angle of 25 degrees to the vertical plane,
the ball (A) of the carburetor bowden control wire
rests against the accelerator pedal lever. See Figure
6E-15.
1. Position accelerator pedal at an angle of 25 degrees
to the vertical plane. To do this, loosen lock nut of
adjusting bolt (c) and unscrew adjusting bolt a few
turns.
Squeeze a 1 3/S” wood block (D) between accelera-
tor pedal and dash panel. See Figure
6E-15.Screw in adjusting bolt until the accelerator pedal
lever releases the wood block (D). Tighten lock nut.
2. Adjust bowden control wire at adjuster. See Figure
6E-16. Prior to doing this, adjust engine idle speed
with engine at operating temperature.
Set carburetor bowden control wire adjuster at the
bracket so that the ball (A) of the control wire rests
against part (B) of the accelerator pedal lever and the
wire core between bracket and segmental disc is not
sagging.

6E- 541973 OPEL SERVICE MANUAL
Figure 6E-21 Removing Vacuum Case Lever
5. Unscrew vacuum diaphragm cover from choke
housing. See Figure
6E-22.Figure 6E-22 Removing Vacuum Diaphragm Cover
6. Unscrew retaining ring from automatic choke
body and take off cover.
7. Unscrew vacuum diaphragm case from carbu-
retor cover. Remove reduction jet. See Figure 6B23.
8. Take float together with spindle and leaf spring
from float chamber.
9. Pull accelerator pump discharge nozzle assemblyFigure 6E-23 Removing Vacuum Case Reduction Jet
out of carburetor housing. Nozzle is press fitted. See
Figure 6E-24.
GATOR PUMPISCHARGE NOZZLE
Figure 6E.24 Removing Accelerator Pump Discharge
10. Remove primary idle jets and secondary idle
plug. Remove primary and secondary high-speed air
jets.
11. Remove primary and secondary main metering
jets.
12. Remove cotter pin from pump connecting rod.
Remove accelerator pump.
13. Remove idle mixture adjusting screw from throt-
tle valve body. Remove idle air adjusting screw from

CARBURETOR AND THROTTLE LINKAGE6E- 55
float chamber. Clean all parts and blow out with
compressed air. Replace gaskets and seal rings.
14. Check actuating parts in automatic choke body,
including diaphragm, for wear. Check pull rod for
free operation. See Figure 6E-25.15. Remove choke assembly by removing choke
valve and 2 choke housing
- to - carburetor screws.
Figure 6E-25 Checking Automatic Choke Parts
16. Check vacuum case assembly. If bushing is worn,
replace vacuum case assembly. See Figure 6B27.
Figure
6E-27 Checking Vacuum Case Brass Bushings
17. Install secondary vacuum diaphragm case assem-
bly. See Figure 6B28.
18. Install gasket and shield between automatic
choke cover and automatic choke body.Figure
6E-28 Installing Vacuum Case Assembly
19. Install automatic choke cover so that the catch
of the
b&metal spring is positioned onto bent end of
the intermediate lever. See Figure 6B29.
Figure 6G29 Installing Automatic Choke Cover
20. Align and tighten automatic choke cover. Choke
valve should be nearly closed at room temperature.
21. Check vent valve for free operation. Valve rod
must not be bent.
22. Screw in jets according to calibration table.
Never interchange parts of the primary and
second-
xy barrel. See Figure 6E-37.23. Install the throttle body to the bowl, using new
throttle body gasket. Adjust secondary throttle valve
gap by loosening lock nut on the secondary throttle

6E- 561973 OPEL SERVICE MANUAL
valve stop screw. Loosen the stop screw until the
valve is completely closed. Turn the screw in l/4turn from closed position, hold, and tighten lock nut.
This is done to insure that the throttle blade will not
stick closed. See Figure
6E-30.PUMPFigure 6E-30 Adjusting Secondary Throttle Valve Gap
24. Install accelerator pump connecting rod in lower
hole of primary throttle shaft lever and cotter pin in
outboard hole at accelerator pump actuating lever
end. Paying attention to proper arrangement of cot-
ter pin and washers. See Figure
6E-2.25. With throttle plate completely closed, there
should be no clearance between the pump levei and
the pump plunger rod.
26. If a clearance is present, loosen 4 accelerator
Figure
6E-31 Accelerator Pump CoverFigure 6C32 Accelerator Pump Cover
pump cover retaining screws and allow the
dia-’phragm spring to push plunger against lever so that
a zero clearance exists. Then retighten the screws.
See Figures
6E-3 1 and 6E-32.27. Insert accelerator pump discharge nozzle so that
the bent tube end points into suction channel of the
primary barrel.
28. Fill the bowl with fuel.
29. With fuel in bowl, slowly open the throttle and
observe the accelerator pump pressure relief valve
exhaust ports and where it seats into the bowl. See
Figure
6E-33. Fuel should not be bleeding back into
the bowl from the exhaust ports or where the relief
valve seats, but a steady stream of fuel should dis-
charge from the discharge nozzle.
30. With fuel in bowl, rapidly open the throttle atid
observe the exhaust ports of the pressure relief valve.
See Figure
6E-33. Fuel should~exhaust’from the ac-
celerator pump pressure relief valve exhaust ports.
3 1. If the pressure relief valve malfunctions, remove
it and replace with a new one.
32. No float adjustment is possible, so check position
of float arm by comparing with a new float of thesame carburetor type. If float arm is bent, replace
float.

CARBURETOR AND THROTTLE LINKAGE6E- 57
ACCELERATOR PUMP
PRESSURE RELIEF
VALVE SEAT
ALVE
VENT DISCHARGE
(AIR BUBBLES FROM THIS
HOLE
IS NORMAL)
PUMP INLET
VALVE EXHAUST
PORT
--6E-33
Figure 6E-33 Carburetor Fuel Bowl
33. Install float and pivot rod making sure rod is
seated in casting.36. Install new air horn gasket so that the holes in
the gasket coincide with the screw holes in carbu-
retor housing. See Figure
6E-35.34. Install leaf spring so that spring ends rest on float
spindle. See Figure
6E-34.37. On vent valve, pay attention to cotter pin position
and arrangement of washers.
3.5. Screw in float needle valve together with copper38. Basic adjustment of idle mixture adjusting screw
seal ring
(.08 in. thick).is 5 turns open.

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\