Page 111
240-84 Fuel injection system
Check for pinched or blocked fue! lines.
Check that the fuel filter is not clogged.
N.B.
lf the fuel filter has been fitted the wrong way
round, it cannot be refitted but must be replaced
by
a new one.
Check the relief valve in the pump. If defec-
tive, fita new pump.
B1E Checking the delivery flow from the
fuel pump
d
Stop the pump by setting the switch to OFF.
Disconnect the return line at the fuel pres-
sure regulator.
Connect one end of the return flow test hose
to the fuel pressure regulator and place the
other end in the graduated beaker.
Start the fuel pump by setting the switch to
ON. Allow the pump to run for 30 seconds
and then read off the volume of fuel in the
beaker (this should be at least 0.9] 0.95
liq qt).
If the pressure drops by more than 0.1-0.2
bar (1.5-2.9 psi) and the delivery flow is
adequate, fit a new fuel pressure regulator.
If the delivery pressure from the fuel pump is
incorrect, perform the checks detailed in
section B1iD.
Saab 900
Page 112
Fuel injection system 240-85
Checking the electrical system
Quick check of the system relay E1 and
fuel pump relay E2
1 Unplug the electronic control unit and the air
mass meter connectors.
2 Connect terminals 17 and 21 of the control
unit connector to earth.
3 Check that current is present at:
¢ The test socket
Pin 9 of the ECU connector
® Pin 2 of the air mass meter connector
e Fuse 14
If current is present in these components. the
system relay, fuel pump relay and associated cir-
cuitry are sound.
if not, follow the steps detailed in Sections E1
and E2.
To remove the system relay/fuel pump
relay
The relay is located on the right-hand wheel arch.
1 Unscrew and remove the sill scuff plate.
2 Remove the weatherstrip from the front door
pillar. Unscrew the anchor plate for the car-
pet from the inner wheel arch panel.
3 Unscrew the air duct and fold it down to-
gether with the carpet.
4 Unscrew and withdraw the relay holder.
Saab $00
Page 113
240-86 Fuel injection system
E1 Checking the system relay
Tools: Multimeter
Jumper lead with crocodile clips
8393 894
1 Unplug the ECU and the air mass meter con-
nectors. Peel back the cover from the ECU
connector. All readings should be made at
the back of the connector. Check that pin 11
of the connector is earthed.
2 Switch on the ignition.
3 Use the jumper lead to connect pin 21 (yel-
low/white; GL/VT) on the ECU connector to
earth. Check that the relay is operating by
checking for current between pin 9 (brown/
white; BR/VT) and pin 11 (black; SV) on the
ECU connector.
if no voltage is present, gain access to the
relay by removing the sill scuff plate, the
weatherstrip and the carpet.
Check for voltage across pin 30 (red: RD) on
the relay and earth and across pin 86 (red;
RD) and earth.
If not, check the leads between pin 30 {red;
RD} and the positive terminal and between
pin 86 (red; RD) and pin 30 (red; RD).
If voltage is present, use the jumper lead to
connect pin 85 (yellow/white; GL/VT) to
earth. Check that voltage is present at relay
pin 87 (brown/white; BR/VT) and 87B (brown/
white; BR/VT). If no voltage is present, fit a
new relay,
if voltage is present, using the jumper lead
check the brown/white (BR/VT) lead from
relay pin 87 to ECU connector pin 9, the
black (SV) lead from ECU pin 11 to-earth, and
the yellow/white (GL/VT) lead from ECU pin
21 to relay pin 85.
Check for voltage at pin 2 (brown/white; BR/
VT) on the air mass meter. lf dead, check the
lead from pin 87B of the system relay.
Saab 300
Page 114
I ESIEOSSDS'' eee
Fuel injection system 240-87
E2 Checking the fuel pump relay
Tools: Multimeter
Jumper lead with crocodile clips
8393894
Jumper lead with switch 83 93 886
Remove fuse no. 30. Connect jumper lead
83 93 886 between fuse no. 30 and fuse no. 27,
28 of 29, to Supply power to the fuel pump. Make
sure that the switch is set to OFF.
1 Unplug the connectors from the ECU, air
mass meter and auxiliary air valve.
2 Connect jumper lead 83 93894 between
pins 17 and 25 of the ECU connector,
3 Check whether the telay is operating by
checking for voltage between the grey/red Switched jumper lead (83 93 886) for power feed
(GR/RD) Limp-home pin on the connector (by to fuel pump. Connect between fuses 27 and 30.
the wiring loom on the RH wheel arch) and
earth.
If not, fold back the carpeting and remove
the relay.
Check for voltage between relay terminal 30
(red; RD) and earth and between rélay termi-
nal 86 (brown/white: BR/VT) and earth,
lf dead, check the red (RD) lead between ter-
minal 30 and the positive terminal, and the
brown/white (BR/VT) lead between terminal
86 and system relay terminal 87 (Turbo
pressure switch).
If voltage is present, connect terminal 85
(violet; VL) to earth using jumper lead
8393894.
Check for voltage at relay terminal 87 (biue/
red; BL/RD) and terminal 87B (grey/red: GR/
RD).
If dead, fit a new relay,
If voltage is present, check the grey/red (GR/
RD) lead between the Limp-home connector
and relay terminal 87B,
Saab 900
Page 115
240-88 Fuel injection system
E3 Checking the pressure switch
(Turbo cars only)
Tools: Multimeter
Pressure pauge 8393514
Cooling-system tester
| 1 Connect pressure gauge 8393514 to the
outlet on the inlet manifold for the hose to
the pressure switch, and connect the cool-
ing-system tester to the branch connection
on the pressure gauge.
] 2 Start the engine. Raise the pressure to the
1 value at which the pressure switch breaks
the circuit, whereupon the engine should
stall.
If the engine fails to stall, check the break-
ing pressure of the pressure switch as fol-
| lows:
Connect the multimeter between terminal
87 on the system relay and terminal 86 on
the fuel pump relay.
| 3 Raise the pressure, The power supply circuit
should be broken when the opening pres-
i sure for the switch is reached (see Section
| 2:4, Technical data). If not, replace the
i | pressure switch.
| E4 Checking the temperature sensor
il (NTC resistor)
Tools: Multimeter
1 Unplug the connector for the ECU and re-
move the cover.
2 Measure the resistance of the NTC resistor: bu. te 4
connect the multimeter across ECU connec- oie aa
tor pins no. 2 (yellow; GL) and no. 11 (black; - igh es
SV); or, alternatively, Unplug the tempera- Me aa
j ture sensor connector and measure the re- Calbia pa
sistance across the pins direct. :
: . ] ®
4. Pee a’ wo .
The resistance varies with the coolant tempera-
ture as follows:
Wl O° (32°F) = 5800 ohm
i 20° (68°F = 26000hm
| 3 If incorrect readings are obtained, discon- 100°C (212°F) = 180 0hm
nect the leads to the NTC resistor. Connect
' the multimeter across the terminals of the
|
. ” Saab 900
Page 116
Fuel injection system 240-89
NTC resistor, and check the values again. if
the readings are still incorrect, fita new sen-
sor. If the NTC resistor is found to be sound,
check the lead between terminal 11 on the
electronic control unit and earth (black: SV)
and between the NTC resistor and earth.
ES Checking and adjusting the throttle-
position sensor
Tools: Multimeter
1 Unplug the connector from the electronic
control unitand remove the cover,
2 Connect the multimeter between pins 3
(grey; GR) and 11 (black; SV) on the ECU con-
nector. Check that the circuit is closed.
If there is a break jn the circuit, check the
grey (GR) lead from pin 3 on the connector to
f the throttle-position sensor, the black (SV)
lead from pin 11 an the connector to earth,
and the black/white (SV//T) lead from the
sensor to earth.
3 Move the throttle butterfly and check the
r reading on the multimeter, If the sensor is
operating properly, the circuit should be bro-
ken the moment the butterfly leaves its
bs home position (position for idling). If not,
| adjust the position of the throttle butterfly
(M1, Basic setting of throttle butterfly).
Saab 900
~—-
Page 117
240-90 Fuel injection system
Slacken the nut and setscrew and then
screw in the setscrew until it touches the
butterfly stop.
Turn the setscrew 1/3-turn more, and lock it
with the nut.
To adjust the throttle-position sensor, undo
the screws securing it to the throttle housing
and turn the sensor until it butts against the
integral stop for idling position. Retighten
the securing screws.
Check that the circuit between ECU connec-
tor pin 3 (grey; GR) and 11 (black; SY) is bro-
ken the moment the throttle butterfly leaves
the stop for idling speed.
Connect the multimeter across pins 11
(black; SV) and 12 (green/red; GN/RD)., If the
sensor is functioning properly, the circuit
should be closed when the butterfly angle is
72° (just before full throttle).
\f the circuit is not closed, check the green/
red (GN/RD) lead between pin 12 on the con-
nector and pin 3 on the throttle-position sen-
sor; the black lead between ECU connector
pin 11. and earth, and the black lead be-
tween pin 2 on the throttle-position sensor
and earth.
If the wiring is found to be good but the sen-
sor is not functioning properly, fit a new
throttle-position sensor,
Throttle-position sensor connector pins
No
3
2
1
Should be connected to:
ECU connector pin 12 (green/red; GN/RD)
Earthing point on the engine (black/
white; SV/VT)
ECU connector pin 3 (grey; GR)
Saab 900
Page 118
Fuel injection system 240-91
E6 Checking the injection valves
Tools: Multimeter
Before starting any checks on the injection val-
ves, unplug the connectors for the electronic
control unit and the air mass meter.
N.B.
The measurements must be made at the back of
the connector for the electronic control unit, with
the cover removed.
1 Unplug the connectors on the electronic
control unit and the alr mass meter and re-
move the cover from the ECU connector.
2 Measure the resistance across terminal 13
(green/red; GN/RD) on the ECU connector
and terminal 87 on the fuel pump relay. The
reading should be 4 ohm. If not, proceed. as
follows:
3 Unplug the connector on the injection valve.
Connect the multimeter across the connec-
tor on the injection valve and read-off the re-
sistance.
The reading for a sound injection valve
should be 16 ohm at 20°C (68°F). If this
reading is not obtained, fit a new valve.
4 If the correct reading is abtained, check the
wiring loom from pin 13 (green/red; GN/RD)
on the ECU connector to the connectors on
the injection valves (via the connection
block). Slide back the rubber gaiters and
connect the meter between the injection val-
ves (via the connection block) and the back
of the ECU connector and also between the
injection valves and the blue/red (BL/RD)
lead from terminal 87 on the fuel pump relay
Saab 900
Page 119
240-92 Fuel injection system
E7A Checking the air mass meter
Tools: Multimeter
Start the engine and let it run at idling speed, *® Check that wiring and connectors are sound,
Check the CO value. If the reading is higher than ® If the wiring is good, plug on the ECU connec-
6%, it cannot be adjusted using the CO adjusting tor.
screw. Switch off the engine.
1 Disconnect the air mass meter from the air 2 Check the burn-off function for the filament
filter. ETB.
Check that the filament is not broken.
If broken:
Change the air mass meter.
If not broken:
Check the alr mass meter connector and wir-
ing loom as follows:
Unplug the air mass meter and ECU connec-
va :
ee)
“Te . «7, ad
Pee dae
ee
: ~* = 4
ee ae nts <n be “a
| OS Bie Beet Oy Sa 2 ei a Pe
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Airmass meter connector
Pin Tocomponentno.
1 ECU connector pin 8 (red/white; RD/VT)
System relay terminal 87B (brown/white;
Bi
RVT)
ECU connector pin 6 (blue/white; BL/VT)
Engine earthing point 552 (black; SV)
ECU connector pin 7 (orange: OR}
ECU connector pin 14 (white: VT)
oOahtw
Page 120
Fuel injection system 240-93
E7B Checking the filament burn-off
function
und. 1 Detach the air mass meter from the air
cleaner and check the filament.
‘inec-
2 Start the engine and run it until it reaches a
temperature of at least 65°C (149°F) and
then let it idle. Revthe engine to 2500 r/min,
release the throttle and allow the engine to
return to idling speed.
ment
3 Switch off the ignition; after about four sec-
onds, the filament should glow brightly for
about one second. If nothing happens,
check the wiring ETA.
4 Start the engine and rev it up to 2500 r/min.
Connect the probes to pins 1 and 4 of the air
mass meter connector. Switch off the en-
gine. After four seconds, the voltage should
= rise to 4V for a duration of approx. one sec-
4 6, ond.
5 If not, check the redAwhite (RD/VT) lead be-
tween pin 1 on the air mass meter connector
and pin 8 on the ECU connector, and the
black (SV) lead between pin 4on the air mass
meter connector and one of the earthing
Pe points on the block,
; @ wy If the leads are found to be sound, test the
j system using a new ECU,
Start the engine and repeat the test proce-
dure. If a correct voltage reading is obtained
| 6
ite but the burn-off function fails to operate, fit
a new air mass meter.
|
N.B
Bs The limp-home function takes over automatically
; if the filament is broken.
—