Page 11
PRESSURE IMPULSE CONTACT AS FROM MODEL
1976
The pressure impulse contact gives acceleration fuel en-
richment when the engine is cold. The contact is mounted
beside the ignition coil and is connected to the inlet sys-
tem via a vacuum hose and is electrically connected to
the ignition coil and the cold start valve.
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PRESSURE IMPULSE CONTACT
The contact is actuated by the change of pressure in the
inlet pipe at accelerations when the cold start valve has
current for a short moment. Provided that the thermo-
time switch at this point is closed (cold engine) is the en-
gine momentarily supplied with an additional amound of
fuel via the cold start valve.
240-8
PRESSURE IMPULSE CONTACT
1, Diaphragm
2. Spring
3. Restriction
4. Spring contact arm
5. Vacuum connection
6. Electrical connections
Valve function: At constant vacuum the pressure is equal
on both sides of the diaphragm depending on the restric-
tion in the center of the diaphragm. When the vacuum is
quickly decreased, the change in pressure is delayed on
the underside of the diaphragm due to the restriction.
This gives the result that the absolute pressure for a mo-
ment is increasing on the upper side of the diaphragm,
causing the diaphragm going down, actuating the contact.
~~
Page 12
AIR SYSTEM
——
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AIR SYSTEM
1. Air cleaner 4. Throttle valve housing
\ 2. Air flow sensor 5. Inlet manifold
3. Rubber bellows 6. Auxiliary air valve
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
Fr) r to the air flow sensor which is bolted to the top of the air
cleaner.
AIR FLOW SENSOR
ie a) 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 flow sensor consists of an air venturi tube in which The air/fuel mixture varies with the load. The inclination
an air flow sensor plate moves. The air flowing into the of the venturi walls therefore varies in stages in order to
venturi from the air cleaner lifts the air flow sensor plate, provide a correct fuel/air mixture at all loads. Thus, the
’ allowing the air to flow through. The greater the amount mixture is enriched at full load.
of air, the higher the sensor plate will be raised.
The air flow sensor plate is fitted to a lever which is com-
pensated by a counterweight. The lever acts on the con-
trol plunger in the fuel distributor which is pressed down
by the control pressure, thus counteracting the lifting
force of the air flow sensor plate.
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THE AIR VENTURI OF THE AIR FLOW SENSOR
SAAB 240-9
Page 13
Checking
GENERAL
Before testing and fault tracing of the Cl system is started,
it must first be established that there are no mechanical
faults in the engine and that the ignition system is func-
tioning properly.
Scrupulous cleanliness must be observed during work on
the fuel system. The surrounding area should be thor-
oughly cleaned before any lines are disconnected.
FUEL LEAKAGES
Check that there are not leakages at the connections and
in the fuel lines. Check around the fuel tank, in the pas-
senger compartment and in the engine compartment.
New seals should be fitted to any leaking connections.
Damaged fuel lines should be replaced.
Check that fuel pipes do not chafe against other objects
(particularly of plastic). CONTINUOUS CHAFING against
e.g. the dip stick sleeve, other fuel pipes or the throttle
cable can result in damage to the fuel nine
AIR LEAKAGES
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 perfomance, owing to the fact
that it by-passes the air flow sensor, causing a lean mix-
ture.
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.
LEVER MOUNTING
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.
9AN—17
'
CAUTION |
Due to the atomization of the fuel, there is a serious |
fire risk when the injection valves and cold start
valve are being tested.
—— eat —
Page 14
AIR FLOW SENSOR PLATE CLEARANCE
Check that there is uniform clearance between the edge
of the air flow sensor plate and the air venturi. The cor-
rect clearance will be obtained automatically when tool
8392474 is used to mount the plate on the lever.
REST POSITION OF AIR FLOW SENSOR PLATE
To check the rest position of the air flow sensor plate,
switch off the ignition (to switch off the fuel pump),
This prevents fuel being injected into the cylinders if the
sensor plate is lifted from its rests position. The top of
the sensor plate should be level with the bottom edge of
the air venturi, This is the highest permissible position
for the sensor plate. A position Slightly beneath the low-
er edge of the venturi (0.02''/0.5 mm max.) is permissib-
le. The position should be checked in line with the lever.
Rest position adjustment is carried out by bending the
loop {A) on the wire underneath the sensor plate. The
air flow sensor must first be dismantled,
PERFORMANCE OF AUXILIARY AIR VALVE
(Checking can only be carried out when the engine is cold.)
Isolate the safety circuit by disconnecting the terminal
on the air flow sensor.
If the “COLD ENGINE CONTROL PRESSURE” (see
below) is also to be checked, the terminals on the warm-
up regulator should be disconnected to prevent the bi-
metal strip from warming up,
Check by means of a torch and a mirror that there is a
elliptical opening in the auxiliary air valve,
Switch on the ignition. The opening should close com-
pletely after about 5 minutes.
If the auxiliary air valve does not close, check the power
supply. If no fault is found, the auxiliary air valve should
be replaced.
A
SENSOR PLATE CLEARA NCE
A. Correct
B. Faulty
S 4489
240-13
Page 15
VOLTAGE ACROSS THE FUEL PUMP
Remove the round cover plate from the top of the fuel
pump (located in the trunk compartment) and measure
the voltage between the positive and negative terminals
when the pump is operating. The lowest permissible volt-
age is 11.5 V. Disconnect the terminals connecting the
pump to the air flow sensor and the warm-up regulator if
these are to be checked later.
FUEL PUMP CAPACITY
Provided that the fuel filter is not clogged and that the
battery is properly charged, the pump capacity can be
checked by measuring the return fuel in the following
way.
Connect a hose to the connection for the fuel return line
at the air flow meter. Place the other end of the hose in
a container. Disconnect the relay for the injection system
and connect a jump lead between terminals 30 and 87,
Switch on the ignition and allow the pump to run for
about 30 seconds. Measure the quantity of fuel (refer
to the specifications in Group section 022).
WARM-UP REGULATOR
Check the warm-up regulator line as follows:
Disconnect the terminal from the warm-up regulator and
connect a voltmeter across the contacts in the connector.
Ensure that the ignition is switched on and that the safe-
ty circuit connection at the air flow sensor has been with-
drawn. The lowest permissible voltage is 11.5 V.
Check that there are no brakes in the coil of the regulator
by connecting a buzzer or test lamp in series with the coil.
|f the coil is found to be damaged, the warm-up regulator
should be replaced.
240-14 SAAB
Page 16
PERFORMANCE AND TIGHTNESS OF INJECTION
VALVES
The injection valves can be checked as follows:
1. Remove the rubber bellows from the air flow sensor,
2. Unscrew the injection valves from the inlet manifold
and place them in a suitable container. The fuel lines
should be left connected.
3. Switch on the ignition and withdraw the safety circuit
plug from the air flow sensor. This enables the fuel
Pump to operate.
4. Fuel atomization: Lift the lever in the air flow sensor
and check the spray form emitted at the injection valv-
es. If the atomization is poor, see under “Cleaning of
injection valves” for further details.
5. Valve tightness: Switch off the ignition to obtain the
rest pressure. Wipe dry the area around the injection
valve nozzles. Lift the lever and check for leakage. It
should not take less than 15 seconds for a drop to
form. In the case of excessive leakage, see under
“Cleaning of injection valves’.
PERFORMANCE AND TIGHTNESS OF COLD START
VALVE
Withdraw the plug of the cold start valve and unscrew the
latter from the throttle valve housing, allowing the fuel
line to remain connected,
Connect a wired plug to the cold start valve and connect
the wires to the main beam terminal and body of one of
the headlights.
Switch on the ignition and disconnect the electrical con-
nection to the air flow sensor. The fuel pump is now run-
ning. Place the cold start valve in a container and have an
assistant switch the headlights to main beam for a short
period (30 seconds max.). Fuel should spray out of the
valve during this period.
Dry the valve nozzle and let the fuel pump run for a fur-
ther minute. No fuel should pass through the valve during
this time.
THERMO-TIME SWITCH
When the engine temperature is below approximately
113°F (+45°C), current is allowed to flow for a certain
period (depending on the temperature) while the starter
motor is running.
r
CAUTION
Due to the atomization of the fuel, there is an acute |
fire risk in conjunction with testing of the injection |
valves or the cold start valve.
240-15
een,
Page 17
Check that the switch closes when the engine is started
by means of connecting a test lamp in series across the
contacts of the cold start valve plug.
It is not possible to make a more accurate check of the
cut-in time or temperature. If the condition of the switch
is at all in doubt, it should be replaced.
PRESSURE READING qo =]
General
Connect pressure gauge 83 92 516 as follows:
Disconnect the contro! pressure line from the fuel distri-
butor and connect the pressure gauge between the fuel
distributor and the line to the control pressure regulator.
CAUTION
The safety function is governed by a pulse sensor
in the pump relay which is actuated by the igni-
tion pulses.
Disconnect the fuel pump relay and connect a jump
lead across terminals 30 and 87 in the relay holder.
Thus, the fuel pump will cut in as soon as the ignition
is switched on.
Page 18
Bleed the pressure gauge by repeated opening and closing
of the valve with the pressure gauge directed downwards
and the fuel pump connected.
Cold engine control pressure
Carry out this test if poor engine performance has been
experienced during cold starting and the warming up pe-
riod.
The test can only be carried out when the engine is cold.
The engine should not be run for a longer period of time
(e.g. overnight) before the test can be carried out, to en-
sure that the engine is at ambient temperature. The en-
gine must not be run before this test.
Open the valve, disconnect the plug at the warm-up regu-
lator and switch on the ignition.
Compare the pressure gauge reading with the recommended
pressure given in the temperature/pressure graph. Refer to
the test values in section 022.
If the values should differ, replace the warm-up regulator.
Warm engine control pressure
Carry out this test when poor performance has been ex-
Perienced when the engine is warm.
Open the valve.
Connect the warm-up regulator plug.
Leave the ignition switched on until rest pressure is pre-
sent.
Refer to the test values in section 022.
If the value should differ, replace the warm-up regulator.
240-17
Page 19
Line pressure
Close the valve.
- Switch on the ignition.
Refer to the test values in section 022.
If the line pressure should differ from the recommended
values, this may be due to: ;
In the case of insufficient line pressure:
Insufficient pressure from the fuel pump
Blockage of the strainer in the tank
Leakage in the fuel line
Line pressuré regulator being faulty
In the case of ec
In the case of excessive line pressure:
Blockage of the return line
Line pressure regulator being faulty.
For adjustment of the line pressure see under “Mixture
control unit, line pressure regulator’.
Leakage tests on the whole system
The test should be carried out after unsatisfactory perfor-
mance arising from warm-engine starting.
If the engine is cold, the bi-metal strip in the warm-up re-
gulator must be heated and kept warm during the test.
Unplug the connector on the warm-up regulator and re-
place it with a plug connected directly to the battery.
Open the valve. Switch on the ignition until "’warm en- ”
gine control pressure” is reached, and then switch off the
ignition.
Observe the pressure drop on the pressure gauge. Leakage
can generally be established after 3 or 4 minutes. In cases
of uncertainty, carry out the test for 20 minutes. Refer
to the test values in section 022.
If the pressure drops too rapidly, the fault can be located
by conducting the test with the valve closed.
If the values obtained from this test are correct, then the
warm-up regulator is faulty.
If the pressure drop is still excessive, the following com-
ponents could be faulty:
The fuel pump
The fuel distributor
The injection valves
The cold start valve
\f the O-ring of the line pressure regulator is damaged,
leakage may occur. For replacement of the O-ring, see
under ‘’Mixture control unit, line pressure regulator”’.
240-18
Page 20
CO-METER CONNECTED
3. Catalyst cars model 1979:
— Remove the large bore hose at the charcoal canis-
ter.
~ Connect the CO-meter sond to the exhaust pipe.
— Make loose the oxygen sensor wire (the wire may
not come in touch with earth).
THE OXYGEN SOND |S DISCONNECTED
3. Catalyst cars model 1980:
— Remove the plug in the front exhaust pipe and
connect the CO-meter to the pipe with the aid of
connecting piece.
240—20
CO-METER CONNECTED
Make loose the oxygen sensor wire (the wire may
not come in touch with earth).
THE OXYGEN SOND IS DISCONNECTED
4, Read off and adjust the idling speed and CO-value.
Before each reading, rev up the engine and then allow
it to return to steday idling speed. Wait troughly 30
seconds before reading of the CO-value.
| Non catalyst cars model 1978
Non catalyst cars model 1979
Catalyst cars model 1979
|
| Catalyst cars model 1980
Canada cars (excl. Turbo)
1.25 + 0.75 %
0.75 +0.25 %
0.75 + 0.25%, (sensor disconn.
after catalyst)
1.0 + 0.25 % (sensor disconn,
before catalyst)
1.5405%