Page 91
High-speed system
At higher speeds and heavier loads, fuel is supplied to the
engine through the main system of the carburetor The
fuel passes the main jet before reaching the emulsion tube
pressed into the carburetor body.
As the fuel passes through the emulsion tube, an amount
of air determined by the emulsion jet is mixed with it.
The obtained mixture of fuel and air then flows into the
neck of the carburetor through an atomizer.
HIGH-SPEED SYSTEM
1. Cover plate
2. Emulsion jet
3. Emulsion tube
4. Main jet
5. Choke tube
Febr 1977
Page 92
Econostat system
In order for :
full-load oe ith to receive enough fuel at higher
system known ‘ the carburetor is provided with a booster
daicaalh ihe cr This works parallel with
tr is fed directly from the float cham-
The system i
consists of a calibrated riser which is press-
ECONOSTAT SYSTEM
1. Riser
2. Spray pipe
200—10
SAAB
fitted in the float chamber cover. From the riser, a dy
leads to the atomizer pipe which is also press-fitted re
the cover. The opening of the atomizer pipe is placed in
arburetor at a point where a slight va
peed and low load. Only as the =
5 the vacuum at this point kcal
fuel to be drawn up through the e
the neck of thec
uum prevails at low $
and load increase doe
high enough to cause
riser.
Febr 1977
Page 93
or
Acceleration system
if the throttle valve is opened quicki
ture tends to be lean. The reason for
moves more easily than the fuel and
gine sooner.
To compensate for this, a certain amoun
fore injected into the engine with the ai
tion pump. The latter, which is located
side of the float chamber, is a diaphrag
works with a spring-loaded link from t
The fuel to the acceleration system is sucked from the
float chamber via an inlet valve inside the acceleration
pump. Pump strokes cause the inlet valve to be closed
Y, the air-fuel mix-
this is that the air
thus reaches the en-
d of the accelera-
On the right-hand
™M Pump which
he throttle valve,
t of fuel is there-
and the fuel is forced past the ball in the inlet duct and
Out into the throat of the carburetor via acceleration jet
and injector tube.
When injection ceases and the diaphragm returns to the
normal position, the ball closes the outlet duct and fuel
fills the acceleration pump again through the open inlet
valve.
The acceleration pump is connected with the float cham-
ber via a small leakage hole in order to prevent accelera-
tion fuel from flowing into the engine when it expands seaaral
on account of the carburetor getting warm. This has made iii
Heneenneny
it necessary to increase the pump stroke. BY
oeeeeenee
seeebenes
seeeneneny
UE,
seine
uF 8
eeeneennnee
POUT
ACCELERATION SYSTEM
1. Injector tube
2. Acceleration jet
3. Ball
4. Leakage hole
5. Outlet duct
6. Spring
7. Control link
8. Lever
9. Diaphragm
10. Inlet valve
Febr 1977
Page 94
CARBURETOR FOMOCO, MODEL 1969-1970
As from model 1969 the car is equipped with a FoMoCo
down-draught carburetor. The fuel feeding is regulated
by fixed jets mounted in the carburetor body. Only the
main jet is removable. In the body there are drilled fuel
ducts, and also air ducts. In the emulsion tube is — at an
early stage — a certain amount of air being mixed in with
the fuel.
The carburetor has an automatic choke device with fast
idle and accelerating pump. The carburetor differs from
the Solex carburetor previously used, especially by it that
only the main jet is removable and the fast idle device sit-
uated on the outside of the carburetor. The fast idle has
four steps out of which the fourth step is engaged at the
start only. As soon as the accelerator pedal is touched
upon, the said step is disengaged independently of the
cooling water temperature, Then fast idle works with
three steps like the Solex carburetor previously used.
Adjustment of fast idle, accelerating pump capacity, float
chamber ventilation and float level is made by bending
control rods and levers. These have, at the factory, been
adjusted to prescribed measurements, and a readjustment
at the garage is therefore — as a rule — not required.
a 3222202123 25 26
33 34
A. —
= = i — : : I lw oo wage
200-12
‘Lr
5
CARBURETOR, MODEL 1969-1979 2429 28 27
17 ic spri ;
2. Pine atlbates 13. Throttle valve
3, Choke plate shaft . bs Accelerating Pump rod 25. Control piston
4. Choke plate 1 elerating Pump lever 26. Vacuum Passage
5. Main jet ie Thermostatic Spring 27. Inlet valve
6. Float needle vaive 18. ieee Piston . Pressure-equalising hole
7. Step cam * Vacuum pa - Pump disch ssage
8. Float with shaft 19. Idle air jet 30. Ball check sg
9. Diaphragm piston = Idle air channel, mix; and weight gees
10. Vent actuating lever 2. fuel "9 air 31, Pump jet
11. Idle adjusting screw 23. SOrrection jet 32. Vent tube
12. Idle mixture control screw - Mixing tube
24. Full load enrichment
Saag
33. Vent Push rog
* Fuel supply tube
ons
—l @
S$ 2142
a
Page 95
CARBURETOR FOMOCO, MODEL 1971-1975
In order to satisfy the demands on cleaning of th
haust gases, the engine is equipped with aoe . ex-
buretor. This carburetor differs from ‘isiterse sion al
lier models in that it is made with narrower ote in ear-
and each carburetor has been subjected to a ey
The following descriptions are vali
d for F
retors model 1969—1975,. OMoCo carbu-
CARBURETOR, MODEL 1971-1975 HE
oer
of 2616141517 19 20 26 9
— = ms = ais 3 = coosmmnen alas
S f :
27 7 1823 2221 Pe
CARBURETOR, MODEL 1971-1975
1. Automatic choke housing 10. Thermostatic spring 19. Control piston
2. Choke plate 11. Vacuum piston 20. Vacuum passage
3. Connection for float chamber vent 12. Vacuum passage 21. Ball check valve (inlet)
4. Step cam 13. Idle air jet 22. Vent
5. Idle adjusting screw 14. idle air channel 23. Pump discharge passage
6. Vacuum nipple 15. Idle fuel channel 24. Ball check valve (discharge) and weight
7. idle mixture control screw 16. Air correction jet 25. Pump jet
8. Accelerating pump 17. Mixing tube 26. Vent tube, float chamber
9. Fuel supply tube 18. Full load enrichment 27. Main jet
SAAB wots
Febr 1977
Page 96
Float system
The fuel level in the float chamber is governed by the
float. When the fuel flows into the chamber, the float is
lifted and presses the valve against the seat. Once the in
tended level is obtained, the fuel supply is cut off. When
the level sinks, the course is repeated.
vel. the needle valve is equipped
; ble float level,
nsure a Sta
Toe d ball.
-ing-loade
s ra aor is equipped with a valve, which governs
u
el ae of the float chamber. When the throttle
the vent!
vaive isc osed tt e ven
i | Pp )
wes open inwa ds i.e. to the ca bureto eck.
tilation is directed outwards,
FLOAT SYSTEM
1, Fuel intet
2. Float needle valve
3. Float
4. Vent push rod
D ‘
V
\
\
\
\
\
\
\
!
3. Lever
4. Spring
FLOAT CHAMBER VEN
1, Float chamber ventilat
2. Vent push rod
TILATION
on
200-14 SAAB
rope 1977
Page 97
Starting automatics
To facilitate cold-startin , th ‘
with a choke plate in shecapescyen, te wees
neck. When the plate is closed tk i eras
Me vacuum under it in-
creases and so does the fuel supply.
The choke plate is regulated automatically by means of
a thermostatic spring the function of which is directly
dependent on the prevailin coo!
choke plate is closed as ws as va eel ies ta
cold, but
as the temperature of the cooling water ri
plate gradually opens and is wide o
of approx. 140°F (60°C),
The starting automatics feature a vacuum-regulated piston
which, via a lever, open the choke plate slightly as soon
as the engine has started, thus providin
air and preventing “suffocation”.
Furtermore, there is a mechanical device which forces
the choke plate to open, then the vacuum falls due to
remarkable acceleration.
The starting automatics include a step cam chich serves
to increase the idling speed when starting from cold, In
order to engage the fast idle device when starting from
cold, the accelerator pedal must be pressed right down
and then released before an attempt to start is made. This
is necessary in order to release the step cam thus enabling
the latter to take up the position decided by the thermo-
static spring.
The position of the throttle valve is then not governed
by the idling screw any longer but by the position the
stop on the step cam.
ses the choke
pen at a temperature
g sufficient engine
Automatic choke (Modulating choke) as from carburetor
71 TW—JD
USA cars as from carburetor 70 TW—AA
The choke flap is regulated in the same manner as before
by a bimetal spring which reacts to the coolant tempera-
ture,
When the engine is started, a vacuum-actuated piston is
drawn downwards ina cylinder bore and, if the engine is
cold, the choke flap opens somewhat. This is done by a
lever and is necessary in order to supply the engine with
enough air so that it will not ‘suffocate’. The new design
differs from the old one in that there are two slots along
the bore of the cylinder. When the piston descends about
3mm (0.12) the inner slot is exposed above the top of
the piston, and when the latter descends a further 4 mm
(0.16’’) the outer slot is also exposed. Atmospheric air
can then flow through the slots to relieve the vacuum on
the underside of the piston, so that the position of the
choke flap is adjusted to the load on the engine. In the
older type the choke flap opens by about 4,5—5 mm
(0.18—0.20’) with the piston all the way down. The new
type has a longer cylindar bore, so that the choke flap is
wide open when the piston is all the way down.
STARTING AUTOMATICS
1. Thermostatic spring
2. Vacuum piston
3. Lever
5, Vacuum passage
|
: Febr 1977
4, Thermostatic spring lever
6. Fast idle stop dog
7. Step cam
8. Link rod
9, Choke plate shaft
10. Choke plate
200—15
Page 98
Idling system
When the engine is idling, the throttle valve is almost
fully closed (regulated by the idling screw) so that there
will be a large vacuum under the throttle valve.
The vacuum in the idle air channel emanating under the
throttle valve, will then be so great as to cause fuel to be
drawn up through the main jet and through a special idle
fuel channel up to the idle fuel jet, consisting of an accu:
rately calibrated constriction of the channel. The fuel as
then partly mixed with the air admitted through a special
pale on-
air channel. The fuel-air mixture then passes another c
receives more ait from a Pressure-equalising
ich is placed further down in the neck of the Car.
hole, whic urpose of this is to get the correct rela-
buretor. San fuel and air, before the mixture — yjg
ee control screw — is suctioned into the engine.
striction, and
the Si to make the transition from idling system to
E ‘ :
In fa system more uniform, there is — in the carburetor
mai
k, just above the idle mixture control screw — a slot,
neck,
hich becomes visible when the throttle valve is Opened.
whi eceives its fuel from the idling system,
This system F
—
4
200—16
Hk > HE
IDLING SYSTEM
1. Idle air jet
2, Idle air channel, mixing air
3. Idle fuel channel
4. Idle mixture control screw
S 5274
Febr 1977
Page 99
—e_-=- —-—
Main system
At higher speeds and heavier loads, fuel is supplied to
the engine through the main system of the carburetor
The fuel passes through the main jet before reaching the
mixing tube pressed into the carburetor body. As the
fuel passes by the mixing tube an amount of ait deter-
mined by the mixing tube is mixed with it. The obtained
mixture of fuel and air then flows into the neck of the
carburetor through a spray pipe.
on
fein
ELTA |
Febr 1977
In order for the engine to receive enough fuel at higher
full-load speeds, the carburetor is provided with a vacuum
regulated full-load-enrichment system. The system con-
sists of a piston, which via a channel communicates with
the carburetor neck. The piston is actuated by the vacu-
um prevailing in the neck. When the engine speed is low
and the throttle valve closed, the vacuum is large and the
piston is lifted, and a spring-loaded valve — situated close
by the main jet — kept shut. When the throttle valve is
wide open, the vacuum diminishes and the piston is de-
pressed by a spring, which opens the valve. The fuel then
flows direct into the main system through the main jet.
2 5 6
=
Wi
ce >
3:4
MAIN SYSTEM
1. Air correction jet
2. Mixing tube
3. Main jet
4, Full load enrichment
5. Control piston, full load enrichment
6. Vacuum passage
7. Spray pipe
S 2134
200-17
Page 100
Acceleration system
If the throttle valve opens quickly, the air-fuel mixture
tends to be lean. The reason for this is, among other
things, that the air moves more easily than the fuel and
thus reaches the engine sooner.
To compensate the “leanness”, a certain amount of fuel
is therefore injected into the engine with the aid of the :
accelerating pump. The latter is a diaphragm pump whic
works with a spring-loaded link from the throttle valve.
The fuel to the acceleration system is sucked from sd
float chamber via an inlet valve inside the accelerating
pump. Pump strokes cause the inlet valve to close and
the fuel is forced past the ball in the outlet duct and out
into the carburetor neck via the acceleration jet.
2
NN
injection ceases and the diaphragm returns to the
|
When | closes the outlet duct and fuel
ition, the bal
mal position, ' :
fi the accelerating pump again through the open iniet
ills
cite outlet duct of the acceleration system, there js —
n the
he ball — a weight which serves as non-return
above t fuel supply to the acceleration system is regu.
valve. Mig that a certain pressure is required to lift the
ere the weight. In this way fuel injection is preven.
re when the valve opens slowly.
|
$2135
3 9 45 67 8
ACCELERATION SYSTEM
1. Ball check valve (discharge) and weight
2. Acceleration jet
3. Fuel channel
4. Pressure-equalising hole
5. Vall check valve (inlet)
6. Spring
7. Diaphragm
8. Lever
9. Accelerating Pump rod
200-18 SAAB
rove 197