Page 211
Checking the fuel-boosting function, turbo
A. Checking the throttle valve switch, solenoid valve and
pressure regulator should be carried out in conjunction with measuring of the CO emission as follows:
1. Run the engine until hot, connect the CO meter
and check that the CO content in the exhaust gases
is as specified ( 1.5 ± 0.5 %)
S 5202
CHECKING THE CO CONTENT
2. Press in the actuating arm on the throttle valve
switch and keep it depressed. The CO value should
now increase to about 4-6% CO.
3. Release the actuating arm and check that the CO
value is 1.5 ± 0.5 %.
13.Checking of the speed transmitter should be carried
out in conjunction with checking of the CO setting as
follows. 1979 model.
THE THROTTLE VALVE SCHWITCH ARM IS ACTUATED
1. Run the engine until it is warm, connect a CO meter
and check that the CO value in the exhau_stgases is
within the prescribed limits (1.5 ± 0.5% CO).
2. Disconnect the cable from the front of the speed
transmitter and connect drive cable 83 93 126 to
the speed transmitter.
3. Connect a variable-speed portable drill to the other
end of the drive cable. By means of the drill, set
the cable rotating and observe the reading on the
speedometer. At speeds in excess of 80 ± 3 mph
;130 ± 5 km/h), the CO value should increase to
approximately 4-6% CO.
N.8.
Drive cahle 83 93 126, is equipped with an angle
drive unit which causes rotation in the reverse direction in order to produce a reading on the
speedometer.
SAAB
240-9
Page 212
FUEL BOOSTING SYSTEM, TURBO MODELS 1980-
§ RI=====::::
General
Ello
The fuel boosting device serves a double function: it
assists in the internal cooling of the engine when it is subjected to sustained periods of high load and it also provides the extra fuel required for rapid acceleration.
Fuel enrichment is achieved using a special warm-up
regulator/boost control which is regulated by the compressor pressure through a control system.
0
7
---------------,
I
4
S 7294
The control system consists of:
1. Pressure outlet in the throttle housing
(before the butterfly)
2. Delay valve (6 sec.)
3. Non-return valve
4. Pressure tank
5. Electrical control valve
6. Throttle valve switch (62° throttle opening)
7. Warm-up regulator/boost control
FUEL BOOSTING SYSTEM
1. Pressure tank
2. Electric control valve
3. Delay valve (6 s)
4. Non return valve
The control system has the following two functions:
L High load (partially-opened throttle)
Pressurized air from the compress~r passes via the delay valve through the electrical control valve which is
its normal position passes the pressurized air on to the
warm-up regulator/boost control.
The delay valve ensures that the fuel boosting system
is not activated for temporary increases in load which
would otherwise result in an unnecessarily high petrol
consumption and unwarranted hydrocarbon emission.
240-10
S 7295
SAAB
Page 213
11.Wide-open throttle
The pressure tank is connected to the compressor via
a non-return valve which enables it to retain pressurized air for a long period.
When the throttle is wide open the throttle valve switch
activates the electrical control valve, the residual pressurized air providing an immediate boost.
S 7296
In addition to the ordinary steel diaphragm valve the warmup regulator/boost control has a rubber diaphragm which
is activated by the boost from the compressor. The spring
pressure of the steel diaphragm is reduced at approx. 0.4
bar charging pressure, thereby reducing the boost.
!Checking the operation of the fuel boosting device
'Turbo MB0- (to be included in the 15,000 km (10,000 m)
iiervice
A. High load (partially-opened throttle)
1. Run the engine at idling speed with the CO meter
attached (engine warmed up)
2. Remove the pressure hose from the butterfly housing
and connect meter 8392813 (pressure gauge for
checking charging pressure) and a cooling system
tester to the hose. Seal off the connection on the
butterfly housing.
CO%
S 7156
3. Increase the pressure to 0.80 bar (due to the presence of the delay valve the pressure should only be
recorded once the level has stabilized).
4. Check that the CO reading has increased to 4-6 %
approx.
UMt
240-11
Page 214
B. Wide-open throttle
5. Remove the pump and note that the CO reading re•
turns to the original figure recorded.
6. Depress the lever on the thrott.le valve switch.
,
7. Check that the CO reading increases to 4-6 % approx.
2
CO%
Residual pressure
S 7156
It is essential that the pressure tank and connections are
completely air-tight in order that the fuel boost required
in the initial stages of acceleration can be provided. Fai·
lure here means that fuel enrichment can first be achieved
only once the charging pressure has reached a sufficiently
high level.
Checking residual pressure
1. Connect pressure gauge 8392813 (for checking the
charging pressure) between the non-return valve and
the pressure tank.
2. Connect a cooling system tester in front of the non•
return valve and increase the pressure to 0.8 bar.
3. Check that the pressure has not dropped below
0.6 bar after 5 min.
S 7299
Q
S 7378
240-12
SM.B
Page 215
AIR SYSTEM
S 5626
AIR SYSTEM
1. Air cleaner
2. Air flow sensor
3. Rubber bellows
4. Throttle valve housing
5. Inlet manifold
6. Auxiliary air valve
240-13
Page 216
AIR CLEANER
The air cleaner is fitted to a bracket mounted on the
front part of the left-hand wheel housing. The air cleaner
contains a paper cartridge. The air flows through the inlet
pipe into the air cleaner, through the air filter and upwards
to the air flow sensor which is bolted to the top of the air
cleaner.
The lever acts on the control plunger in the fuel distributor by means of an adjustable link with a needle bearing
at the contact point. The basic fuel setting, and thus the
CO setting, is adjusted by means of the adjustment screw
on the link. This adjustment is made by means of a special tool and access to the screw can be gained through a
hole in the air flow sensor between the air venturi and the
fuel distributor.
RUBBER BELLOWS
Al R FLOW SENSOR
The air flow sensor consists of an air venturi tube in which
an air flow sensor plate moves. The air flowing into the
venturi from the air cleaner lifts the air flow sensor plate,
allowing the air to flow through. The greater the amount
of air, the higher the sensor plate will be raised.
The air flow sensor plate is fitted to a lever which is compensated by a counterweight. The lever acts on the control plunger in the fuel distributor which is pressed down
by the control pressure, thus counteracting the lifting
force of the air flow sensor plate.
The rubber bellows connect the air flow sensor to the
throttle valve housing.
THROTTLE VALVE HOUSING
The throttle valve housing is connected to the inlet manifold and, in addition to the throttle valve, it contains the
idling air passage and the idling adjustment screw, connections for the hoses to the auxiliary air valve, and the cold
start valve and the vacuum outlet for ignition setting.
As from model 1976, an deceleration valve is fitted in
the throttle valve (see section 254).
INLET MANIFOLD
The injection valves are mounted in the inlet manifold.
The valves inject the fuel into the inlet passages at the
joint between the inlet manifold and the cylinder head.
A thermo-time is mounted inside the inlet manifold and
this senses the temperature of the coolant in the cylinder.
The manifold also contains outlets for pipes to the brake
servo unit and outlets for crankcase ventilation.
S4483
AIR FLOW SENSOR
The height to which the air flow sensor plate is raised is
governed by the magnitude of the air flow.
The air/fuel mixture varies with the load. The inclination
of the venturi walls therefore varies in stages in order to
provide a correct fuel/air mixture at all loads. Thus, the
mixture is enriched at full load.
S4484
THE AIR VENTURI OF THE AIR FLOW SENSOR
240-14
SA.Ml
Page 217
AUXILIARY
ELECTRICAL SYSTEM
AIR VALVE
The function of the auxiliary air valve, together with the
warm-up regulator, is to compensate for losses due to friction and condensation in the inlet manifold and combustion chamber on cold starting, so that the required idling
speed will be obtained. The valve is located in a passage
which by-passes the throttle valve. The air flowing through
the auxiliary air valve has also flowed through the air flow
seinsor, so a fuel quantity is obtained which corresponds
to the air flow.
The valve is actuated by a bi-metal strip which opens the
valve completely when the engine is cold. When the engine is started, current flows through a coil and heats up
the bi-metal strip, gradually closing the valve. When a hot
engine is to be started, the engine temperature acts on
the bi-metal strip and the valve remains closed.
1
Up to and including early 1977 model (with safety switch
on the air flow censor).
When the ignition is switched on, current flows through
the safety relay control circuit from terminal 15 on the
ignition coil. The circuit is earthed by means of the contact in the air flow sensor which is now closed. The safety
relay is then actuated.
As the starter is engaged, current flows from terminal 50
to the cold start valve (as from model 1976 via terminal
16 on the starter) and the thermo-time switch, and
through the safety relay contacts via the pump relay control circuit to earth. The pump relay circuit is thereby
closed and current flows to the fuel pump and coils in
the control pressure regulator, and the auxiliary air valve
is energised.
As the air flow sensor plate is lifted, the safety relay control circuit in the air flow sensor will be de-energised. Current to the pump relay will flow via terminal 87a in the
safety relay.
When the starter motor is switched off, current to the
cold start valve and the thermo-time switch will be
switched off.
Should the engine stop for any reason, the contact in the
air flow sensor closes and the pump relay circuit is actuated. Since terminal 87 in the safety relay is dead, no current flows to the pump relay, and the pump switches off
as a safety measure.
S4485
AUXILIARY
AIR VALVE,
COLD ENGINE
1. Bi-metal strip with heating coil
2. Valve
3. Auxiliary air opening
CONNECTOR, THERMO-TIME
SWITCH
1. Green
2. Yellow
S4486
.ll,UXILIARY
AIR VALVE, WARM ENGINE
When the ignition is switched off and the engine stops,
current will cease to flow through terminal 15 of the ignition coil and thus through the whole system.
SA.1'11
240-15
Page 218
\
1
..
9
2
ELECTRICAL
S 5628
SYSTEM, MODEL 1975
2
ELECTRICAL
SYSTEM, MODEL 1976 UP TO EARLY MODEL 1977
1. Fuel pump
2. Contact, air flow sensor
3. Coil, warm-up regulator
4. Coil, auxiliary air valve
5. Thermo-time switch
240-16
SAAEI
6. Cold start valve
7. Fuel pump relay
8. Safety relay
9. Fuse
S 5629
Page 219
As from later 1977 model (with fuel pump relay with
pulse sensor).
The safety function designed to break the circuit to the
fuel pump when the engine stops consists of a pulse
sensor in the pump relay which is actuated by the ignition pulses. If the ignition pulses fail to occur for a period
of one second or more, the relay will break the circuit and
current will cease to flow to the fuel pump and other components in the fuel system.
8
7
4
10
2
8A
10
S 6143
ELECTRICAL
SYSTEM, AS FROM LATER 1977 MODEL
1. Fuel pump
2. Fuel pump relay with pulse sensor
3. Ignition coil
4. Heating coil, line pressure regulator
5. Heating coil, auxiliary air valve
6. Thercno:time switch
7. Cold-start valve
8. Starter motor
9. Service outlet, ignition setting (TSI)
10. Fuse
SM&
240-17
Page 220
r
FUEL LEAKS
LEVER MOUNTING
Check that there are no leaks at the connections and in
the fuel pipes. Check around the fuel tank, in the passenger compartment and in the engine compartment.
New seals should be fitted to any leaking connections.
Damaged fuel pipes should be replaced.
Check that fuel pipes do not chafe against other objects
(particularly plastic).
CONTINUOUS CHAFING against e.g. the dip stick sleeve,
other fuel pipes or the throttle cable can result in damage
to the fuel pipe.
Remove the rubber bellows and check the movement of
the lever in the air flow sensor. As the arm is lifted, a
steady resistance should be felt as a result of the damping
action of the control plunger. No resistance should be
felt when the arm is suddenly pushed down and is not
acting on the plunger. If the air flow sensor has not been
dismantled, a pair of pliers or a magnet should be used to
lift the lever. If any binding is felt, the air flow sensor
must be repaired.
1
,......._
CHECKING THE LEVER MOUNTING
AIR LEAKAGES
AIR FLOW SENSOR PLATE CLEARANCE
Check for leakage in the inlet system between the air
flow sensor and the engine. Air leaking into the system
may result in poor engine performance, owing to the fact
that it by-passes the air flow sensor, causing a lean mixture.
Leakage can occur in the following places:
At the rubber bellows between the air flow sensor and
the throttle valve housing.
At the gasket on the flange of the cold start valve.
At the gasket between the throttle valve housing and the
inlet manifold.
At the gasket between the inlet manifold and the cylinder
head.
At the hose connections on the throttle valve housing,
auxiliary air valve or inlet manifold.
Via the crankcase ventilation hose from the oil filler cap,
dip stick or valve cover gasket.
Check that there is uniform clearance between the edge
of the air flow sensor plate and the air venturi. The correct clearance will be obtained automatically when tool
8392474 is used to mount the plate on the lever.
A
SENSOR PLATE CLEARANCE
A. Correct
B. Faulty
240-18
SAAB
B
S4489