Page 31
200-30 Technical description
Terminal pins on relay P11
The relay has eight terminal pins as follows:
87
31
11
50
TKK
TIP
Feed to relay
Relay earthing point
Terminal for control of Lambda control
unit. Each time terminal 11 is earthed,
the modulating valve opens wide and
provides full-load enrichment.
Signal from starter motor. This signal
initiates the time function of 140 + 20
seconds, during which time full-load
enrichment takes place.
Thermostatic switch.
Through this terminal the relay senses if
the switch is closed or open.
Pressure switch.
Through this terminal the relay receives
a Signal from the starter motor (terminal
16). This initiates fuel boosting each
time the starter is operated, which
continues for three seconds after the
engine has started.
Through this terminal the relay also
receives a signal when the pressure
switch closes (acceleration boost).
The relay also has the following terminals in cars
with manual gearboxes:
TRK
X2
ll
Throttle switch.
Senses whether the throttle butterfly is
open orclosed.
Signal to fuel shut-off relay, which
prevents fuel shut-off when the engine
iscold.
These two functions together render the
enrichment function of the P11 relay in-
operative during deceleration (overrun).
TKK
87
TIP
TRK
31
S 2/4423
Page 32
EC <_<$ es
S 2/423
66
Technical description 200-31
Fuel boosting system
Turbo models without APC
M82 and earlier
The fuel boosting system performs two func-
tions: it assists in the internal cooling of the en-
gine when it is subjected to sustained periods of
load and it also provides the extra fuel required
for rapid acceleration.
Fuel boosting is achieved using a special warm-
up regulator/boost control which is regulated by
the compressor pressure through a control sys-
tem.
Fuel boosting system
1 Pressure vessel
2 Electric contro! valve
3 Delay valve (6 s) (manual gearbox cars only)
4 Non-return valve
The control system consists of:
1 Pressure outlet in the throttle housing (upstream of
the butterfly)
Delay valve (6 s) (manual gearbox cars only}
Non-return valve
Pressure vessel
Electric control valve
Throttle position sensor (62° throttle opening)
Warm-up regulator/boost control
Restriction 2 mm dia. (automatic transmission
only}
ONOURWN
Saab 900
Page 33
200-32 Technical description
The control system has the following two func-
tions:
| Heavy load (not full throttle)
Pressurized air from the compressor flows via the
delay valve through the electric control valve
which, in its normal position, allows the pres-
surized air to pass to the warm-up regulator/
boost control, thus providing fuel boosting.
The delay valve ensures that the fuel boosting
system is not activated for temporary increases
in load which would otherwise result in unneces-
sarily high petrol consumption and unwarranted
hydrocarbon emissions.
Deviations, cars with automatic transmission
(Double connections to the throttle housing)
Under load automatic transmission cars produce
a more powerful signal in front of the throttle. A
restriction immediately adjacent to the throttle
reduces this signal to the desired level.
Cars with automatic transmission do not have a
delay valve because temporary load increases
(pressure increases) do not occur to the same
extent as in manual cars.
ll Full throttle
The pressure vessel is connected to the pressure
generated by the compressor via the non-return
valve, thereby increasing the residual pressure
enough to maintain the same level over a long
period. When the throttle is fully open the elec-
tric control valve is activated via the throttle pos-
ition sensor which immediately regulates the
liné pressure and boosts the fuel accordingly.
This is possible due to the residual pressure in
the pressure vessel.
Saab 900
Page 34
seo
o
he
we
Technical description 200-33
Turbo cars with APC M82 onwards
As from 1982 models, the warm-up regulator/
boost control in Turbo cars equipped with APC is
connected direct to the inlet manifold.
The special warm-up regulator on turbocharged
engines incorporates a steel diaphragm valve.
The pressure of the spring in the valve is influ-
enced by a bi-metal regulator and a rubber dia-
phragm which responds to the pressure gener-
ated by the compressor. At a charging pressure
of approx. 0.4 bar (5.8 psi) the spring pressure
on the steel diaphragm is reduced and there is a
consequent drop in the control pressure.
Overrev limiter for Turbo en-
gines
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 ac-
tuated 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.
The relay incorporates an overrev limiter which
breaks the power to the fuel pump at approx.
6000 r/min.
$2034
1 Pressure outlet in throttle housing, downstream of
butterfly
2 Hose
3 Warm-up regulator/boost control
Saab 900
EEE
Page 35
a
Technical description 200-45
Temperature sensor (NTC resistor)
The temperature sensor is screwed into the inlet
manifold flange. Its function is to provide infor-
mation to the electronic contro! unit about the
temperature of the engine. The control unit then
regulates the quantity of fuel injected according
to the temperature.
S 2/343
When starting from cold and during the first part
of the warm-up period, the engine requires a
much richer fuel/air mixture, owing to the losses
due to condensation in the combustion chamber
and inlet manifold.
As the temperature of the engine rises, the quan- Temperature sensor (NTC resistor)
tity of fuel injected is decreased proportionately. 1 Resistor
2 Body
The temperature sensor consists of a brass body 3 Terminals
which holds an NTC resistor. NTC resistors have:
a low resistance value at high temperatures and
a high resistance value at low temperatures. The
temperature sensor sends a continuous signal to
the electronic control unit.
If the signal from the temperature sensor is inter-
rupted, the signal will be simulated by the elec-
a tronic contro! unit, and the system will function
assuming an engine temperature of 20°C
(68°F).
LH-system ECU
The ECU for the LH-system is located inside the
car, on the RH side underneath the dash panel.
Inside the ECU is a microprocessor containing all
the necessary preprogrammed data, for, @.g.,
maximum rpm, full-load enrichment, filament
burn-off function, etc.
The electronic control unit processes the signals
from the air mass meter and from the other sen-
sors, and using the information contained in its
memory calculates and controls the opening du-
ration of the injection valves. It also contains a
number of auxiliary functions for emitting fixed
signals in the event of a break in the signals from
the air mass meter or temperature sensor:
¢ Air mass meter: the limp-home function.
* Temperature sensor: a simulated signal for an
engine temperature of 20°C (68°F).
Saab 900
Page 36
Fuel system 233-3
N.B.
Always switch off the power to the pump (switch
in OFF position) before connecting any instru-
ments.
Refit in the reverse order.
N.B.
Make sure that the area around the aperture for
the fuel tank is perfectly dry before securing the
clip on the fuel pump collar.
Changing the fuel pump (with
feed pump)
To remove
1 Disconnect the battery leads.
2 Remove the luggage compartment floor and
floor panel and the circular cover over the
fuel pump.
3 Disconnect the electrical leads from the fuel
pump,
4 Disconnect the fuel lines from the pump:
when undoing the banjo fittings, use a span-
ner to stop the pump from turning.
NOOR WNE
Rubber collar
Main pump
Filter
‘O' ring
Receiver
Feed pump
Filter
Saab 900
Page 37
233-4 Fuel system
5 Using a flexible socket driver, slacken the
clip on the collar.
6 Lift the pump complete with pressurized re-
ceiver.
7 Disconnect the electrical leads from the
tank.
8 Disconnect the return fuel line from the re-
ceiver.
9 Lift out the main pump and remove the feed
pump securing screws. Disconnect the elec-
trical leads.
N.B.
If the pump is an early variant, the existing filter
must be replaced with the latest variant. Accord-
ingly, plug (1), washer (2), filter (3), clip (4) and
’O’ ring (5) will become redundant.
Feed pump variant fitted to cars with chassis
nos. as from AE1021336 and AE2009858.
‘ Feed pump, early variant
1 Plug
2 Washer
3 Filter
4 Clip
5 'O' ring
Saab 300
Page 38
To fit
i Connect the electrical leads to the feed
pump: white lead to the positive (+) terminal
and the black lead to the negative (-) termi-
nal.
2 Fit the feed pump and press it up against the
stop.
3 Scribe a mark on the main pump, A mm in
from the end,
Pa: Cars with Cl injection:
“22 Dimension A = 46 + 2mm (1.81 + 0.08 in)
3 Cars with LH injection:
4
Dimension A = 42 + 2mm (1.65 + 0.08 in)
Dimension B = 222 mm (8.75 in)
4 Slide the rubber collar up to the scribed mark
and tighten the clip.
5 Fit the pump in the receiver and position it
according to measurement B. Turn the pump
such that the positive (+) terminal is to-
wards the front of the car.
1 Black
2 White
Fuel system 233-5
Saab 900
Page 39
233-6 Fuel system
6 Connect the return hose and plug on the con-
nector. Lower the receiver into the tank with
the feed pump towards the rear.
7 Connect the electrical leads.
8 Connect the fuel line, using a spanner to
prevent the pump turning when tightening
the banjo fitting.
9 Fit the cover over the fuel pump and replace
the floor panel and luggage compartment
floor,
10 Reconnect the battery leads.
Changing the non-return valve for the
fuel pump
1 Disconnect the negative (-) battery lead.
2 Remove the luggage compartment floor and
floor panel and the circular cover over the
fuel pump.
3 Disconnect the electrical leads from the fue!
pump.
4 Use a spanner to stop the fuel pump turning
and remove the cap nut. Lift off the banjo fit-
ting.
S Remove the banjo fitting with the integral
non-return valve.
Refit in the reverse order.
Saab 300
Page 40
Fuel injection system 240-1
Cl Fuel injection system
Cl Fuel injection system ._ . 240-1 LH Injectionsystem ......... 240-58
Fuel injection system
Checking and adjustments Excessive fuel consumption . . 240-26
Gornitemeeiiie oo iki se. 1. 240- 2 Erratic CO value and idling speed
Fuelleakages........... 240- 2 - difficulty in adjusting ...... 240-27
AiIGAKABEGe Fee 240- 3
Air flow sensor lever mounting . . . 240- 3 Air cleaner element - to change . 240-28
Air flow sensor plate clearance . 240- 4
Air flow sensor plate - rest position . 240- 4 Mixture control unit
Auxiliary airvalve ......... 240- 5 Removal cc: 0meees Sis Ae 240-28
Warm-upregulator ........ 240- 5 Assemblyc3s: 2h 240-29
Thermostatic time switch ..... 240- 6 Fuel: distributon:.<corem sartein Beas cas 240-29
Fuelpump capacity ....... .240- 6 Line pressure regulator ...... 240-29
Voltage across the fuel pum 240- 7
Injection valves - Lever adjustment arm and sensor plate
performance andsealing ..... 240- 7 To remove . Pie Sons aie oar 240-30
Cold-start valve - TOPONE 0 Sates eee 240-30
performance and sealing ..... 240- 8
Checking of pressures Injection valves - replacing . . . 240-32
wa lg | |e OR ee 240-9
Control pressure: engine cold 240-10 Injection valves-toclean ... . 240-33
Control pressure: engine hot 240-10
tees ye ens 240-11 Auxiliary air valve - replacing . . 240-34
Idling settings
ignde apped yes 0 he Am der 240-13 Warm-up regulator - replacing . 240-34
COvalahs Sess; Lee ees 240-13
Connection of exhaust Fuel accumulator
extraction equipment fy oct aa 240-14 Removal/refitting ee axe) tena 240-35
Setting the air-fuel mixture, Fuel filter-tochange ...._. . 240-35
cars with catalytic converters
oe acute nt Cl fuel injection system, Lambda
etting a new air flow sensor - (EU & US specs)
Checking the fuel-boosting Fuel shut-off during engine overrun . 240-36
function, M82 & earlier Turbos Throttle-position sensor,
(N/AcarswithAPC) ....... 240-16 NORTUNIO! oc ene ts eae 240-38
Throttle-position sensor, Turbo . . 240-38
Residual pressure ......... 240-17 Thermostatic switch (45/38 °C) &
Checking the fuel-boosting function isis coe wiht ase sata
ermostatic switch ......., -
Turbo APC cars, M82 onwards . 240-17 Lani Gr cae ee 240-40
Throttle stop - adjusting . 240-19 Fuel booster pressure switch 240-41
PIT time relay’. eee 240-42
Fault diagnosis,Cl system : Deceleration relay, non-Turbo 240-43
Starting difficulties -coldengine . 240-19 Speedtelity i. Gn ee eee 240-44
Starting difficulties - hot engine . 240-20 Electrical system - principle of
Poor running during warm-up operation “Sos he ee ee ee 240-45
period J5r vc a ae a as erate Sa 9 240-22 Component locations ....... 240-47
Zaps sii ~ hot engine . 240-23 Checking: y:. vet. eee 240-48
oily ormance and low top Fault diagnosis chart, Cl Lambda
nv) Se a 240-24 (EU-spec) > See 240-49
Saab 900