Page 121
i
240-94 Fuel injection system
E7C Checking and adjusting the CO
content
Tools: CO meter
Tachometer
Exhaust extraction equipment
Multimeter
4 Connect the CO meter, exhaust extraction
equipment and tachometer.
2 Start the engine and run it until it reaches
normal operating temperature. Check the
CO reading against the specifications (Sec-
tion 0).
If the reading is different to the specified
value, turn the adjusting screw:
® clockwise if the value is too low
® anti-clockwise if the value is too high.
3 If the CO reading is higher than 6% and
therefore cannot be adjusted by use of the
adjusting screw, switch off the engine, un-
plug the air mass meter connector and con-
nect the multimeter across pins 3 and 6 of
the air mass meter connector.
Turn the adjusting screw until the reading Is
380 ohm.
If you cannot obtain this reading, fita new air
mass meter. If the correct reading of
380 ohm |s obtained, plug in the air mass
meter connector, Start the engine and run it
until it reaches normal operating tempera-
ture. Recheck the CO reading, and adjust the
CO content until the correct value is ob-
tained. If the correct value still cannot be ob-
tained, check the air mass meter wiring
loom and connectors (see E7A).
4 If the wiring loom is sound and the CO value
still cannot be adjusted, try fitting a new
electronic contro} unit.
E7D Checking the basic setting of the
fuel Injection system (cars with catalytic
converter)
N.B
There are no specified intervals at which the fuel
system basic setting should be checked or ad-
justed.
This setting establishes a reference point for the
LH system and does not affect vehicle perfor-
mance, Recalibration should be carried out only
when engine function has been disturbed by
major work such as replacement of the ECU
temperature sensor or air mass meter. or after
Saab 900
Page 122
Fuel injection system 240-95
extensive work such as an engine overhaul, cy-
linder head work or timing chain replacement.
1 Remove the plug from the potentiometer
screw located on the side of the air mass
meter.
/ 2 Unplug the loom connector from the air
mass meter.
3 Connect the multimeter (2 kilo-ohm scale)
between pins 3 and 6 as shown. The reading
should be 380 ohm; adjust as necessary by
turning the potentiometer screw. This is the
first step in the basic-setting procedure.
4 Reconnect the air mass meter wiring loom.
| 5 Connect pulse ratio meter 83 93597 to the
test point adjacent to the evaporator hous-
ing using adaptor loom 83 94 132.
6 Start the engine and let it run until the fan
| cuts in.
7 If the basic setting is correct the meter will
oscillate between the ends of the scale.
N.B
The needle will not oscillate or hunt rapidly ac-
ross the scale and there may be a pause between
needle movements.
8 If adjustment is necessary, turn the poten-
tiometer screw as follows:
a If the needle locks at the top of the scale
or settles largely on the high side, turn
the screw anticlockwise until the needle
spends an equal amount of time at either
end.
b lf the needle setties largely on the low
side of the scale, turn the screw
clockwise until the needle spends an
equal amount of time at either end.
G Refit the plug for the potentiometer screw,
Saab 900
2
Page 123
240-96 Fuel injection system
E8 Checking the ECU
Tools: Multimeter
Jumper lead with crocodile clips
8393894
Test lamp
Before performing any checks on the ECU, un-
plug the connectors on the ECU and the air mass
meter and unplug the connector between the ig-
nition system and the distributor,
N.B
The measurements must be made-at the back of
the ECU connector, with the cover removed.
E8A Checking the input signals to the
ECU
1 Unplug the connector for the ECU and re-
move the cover. Disconnect the lead to the
Hall generator.
2 Switch on the ignition.
Check that voltage is reaching pin 18 (green/
white; GN/VT} on the ECU connector,
if not, trace and check the lead from the pin
back to the fuse panel, via the 6-pin loom
connector and terminal block. Also check
the fuse.
3 Connect the jumper lead with crocodile clips
between terminal 24 of the ECU and earth,
Check that current is available at terminal 9
of the ECU. If not, check the yellow/white
(GL'NT) lead between terminal 21 of the ECU
and terminal 85 (brown/white; BR/VT) of the
system relay, and the brown/white (BR/VT)
lead between terminal 9 of the ECU and ter-
minal 87 of the system relay.
4 With the ignition on, check that current is
available between terminals 18 and 11 of
the ECU. If not, check the black (SV) lead be-
tween terminal 11 of the ECU and an ear-
thing point on the block.
Page 124
SSS
Fuel injection system 240-97
Key to the terminals on the electronic
control unit
i:
0) CO hen
aii
Terminal For:
No.
1 Ignition pulse to terminal 1 (blue; BL) ofthe 11 Earthing pointon engine (black; SV)
coll 12 Throttle-position sensor, terminal 3 (green/
2 Temperature sensor (NTC resistor), terminal red; )
2 (yellow; GL) 13 ntral signal to injection valves (green/
3 Throttle-position sensor, terminal 4 (grey; red; GN/RD)
GR] 14 Air mass meter, terminal 6 (white; VT)
4 Idling increase switch, automatic transmis- 15 Earthing point, engine (black; SV)
sion (orange; OR) 16 AC, (red/white; RE
5 Earthing point, engine (black; SV) Ht i Pump relay, terminal 85 (violet; VL)
6 Airmass meter, terminal 3 (blue/white: 18. Ignition switch, termina! +15 (greensvhite:
BLT) GNAVT)
7 Airmass meter, terminal 5 (orange; OR) 19, Limp-home function (violet/white; VLVT)
8 Air mass meter, terminal 1 (red/white; 20 Lambda
RDAT) 21 System relay, terminal 85
9 System relay, terminal 87 (brown/white; 22 Lambda test, (green; GN)
23 AlC valve, (yellow/red; GL/RD)
10 AlC valve. 24 E2K (blue/red; BL/RD)
25 Earthing point on engine (black/white:
SV/VT)
Saab 900
Page 125
240-98 Fuel injection system
5 Connect the jumper lead with crocodile clips
between terminal 17 of the ECU and earth.
With the ignition on, check that current is
reaching terminals 87 and 87B of the fuel
pump relay (or listen to hear if the pump is
running). If not, check the violet (VL) lead be-
tween terminal 17 of the ECU and terminal
85 of the fuel pump relay.
6 With the ignition on, check that current is av-
ailable between terminals 18 and 25 of the
| ECU. If not, check the black/white (SV/VT)
' lead between terminal 25 of the ECU and its
earthing point on the block,
7 Plug in the distributor connector. Check for
an ignition pulse from terminal 1 of the ECU
by connecting the test lamp between the ter-
minal and earth.
Switch on the ignition:
1985 and earlier models: the test lamp
should glow weakly for about a second and
then become brighter. If not, check the blue
(BL) lead between ECU connector pin 1 and
terminal 1 on the ignition coil,
1986 models onwards: the test lamp should
how come on. If not, check the blue (BL) lead
between ECU connector pin 1 and terminal
TD-O of the ignition pulse amplifier,
| 8 Use the multimeter to check the other leads
in the loom from the ECU (check for broken
wires or corroded terminals).
Page 126
EE EEE EE EOE EEE Es
Fuel injection system 240-99
E8B Checking the signals from the
electronic control unit to the Injection
valves
Tools: Screwdriver or stethoscope
Multimeter
Tachometer
1 lf unplugged, reconnect the connectors for
the ECU, air mass meter and the lead be-
tween the Hall generator and the distributor.
Connect the tachometer.
2 Lift up the gaiter on the connector on one of
the injection valves.
N.B
Do not use a test lamp to check the signals from
the ECU to the injection valves,
3 Connect the multimeter probes to the injec-
tion yalve terminals.
N.B
Polarity: Red (+) probe to the blue red (BL/RD)
lead and the black (-) probe to the green/red (GN/
RD) lead,
4 Start the engine and check the voltage read-
ing against the following tables:
Engine temp Voltage
0°C (32°F) iV
20°C (68 °F) 0.6V
80°C (176°F) 0.3V
N.B
The above values are only approximate
5 If the engine is running errati-cally, check
during the warm-up period that all injection
Valves are operating properly. This can be
done by placing a screwdriver or stetho-
scope against the black metal part of the
valve, A clicking sound should be heard if the
valve is aperating.
Saab 900
Page 127
240-100 Fuel injection system
a If one or more of the valves cannot be
heard operating, refer to section E6 on
checking of the injection valves.
b If the injection valves can be heard
operating but the engine still runs errati-
cally at idling speed:
Using a small screwdriver to release the
tension in the spring clips, unplug the
valve connectors, one at a time. This
should produce a marked fall in engine
speed.
c If there is no marked fall in the engine
speed, make a thorough inspection of the
following systems:
© The fuel system
® The injection system
© The electrical system
6 When the engine has reached normal run-
ning temperature, increase the speed
gradually to 3000 r/min. Measure the vol-
tage across the injection valve, which
should rise to 0.8- 0.9V. Let the engine
speed fall to idling speed and then raise [t
rapidly again to 3000r/min; the voltage
should now rise above 0.8 - 0.9 Vmomentar-
ily before falling back to 0.8- 0.9 V again.
E8C Checking the fuel shut-off function
on starting
Tools; Multimeter
When the engine js being turned over on
the starter motor, the fuel supply will be
shut off if the accelerator pedal is fully
depressed to the full-throttle position
(butterfly turned through 72°).
1 Lift up the gaiter on the connector on one of
the injection valves. Connect the multimeter
probes to the injection valve terminals.
Polarity: Red (+) probe to the blue/red (BL/
RD) lead and the black (-) probe to the green/
red (GN/RD) lead.
2 Run the starter motor and check that voltage
Saab 900
Page 128
Fuel injection system 240-101
iS present across the injection valve,
3 Fully depress the accelerator pedal.
4 The injection valve should now remain de-
energized throughout the time the starter
motor is running. If not, check the operation
of the throttle-position sensor (E5) and re-
place it if faulty. Check the green/red (GN/
RD) lead between terminal 3 on the throttle-
position sensor and terminal 12 on the ECU.
Check the lead between terminal 2 on the
throttle-position sensor and its earthing
point on the block.
E8D Checking the full-load enrichment
function (N/A cars with catalytic conver-
ye 0 ter)
Tools: CO meter
Multimeter
Jumper lead
1 Connect the CO meter and exhaust extrac-
tion equipment.
2 Start the engine and run itto Normal temper-
ature,
3 Slide back the gaiter on the connector on
one Of the injection valves. Unplug the con-
nector from the throttie-position sensor,
peel back the connector rubber and connect
w a a jumper lead between pins 3 and 18.
y 4 Check that the CO value increases by about
1%. If not, connect the multimeter across
| the terminals of the injection valve.
N.B
Polarity: Red (+) probe to the blue/red (BL/RD)
lead and black (-} probe to the Breen/red (GN/RD)
lead.
Check that the voltage rises by approx. 0.1 V.
5 If the voltage does not rise, check the leads
to the ECU (see E5). If the wiring is sound, try
fitting a known good ECU,
| 6 Check and adjust the CO content as de-
scribed in section E7C.
Saab 900
Page 129
240-102 Fuel injection system
ESE Checking the warm-up period
Tools: Multimeter
CO meter
Tachometer
4 Connect the tachometer, CO meter and
| exhaust extraction equipment.
2 Start the engine.
| 3 Slide back the gaiter on the connector on
| one of the injection valves.
4 Connect the multimeter probes to the can-
nector pins.
N.B
Polarity: Red (+) probe to the black/red (BL’
. RD)lead and the black (-) probe to the green/red
| (GN/RD) lead.
5 Check the engine speed during the warm-up
period. The engine speed should decrease
as the engine temperature rises.
6 Measure the voltage across the injection
valve and compare the reading with the
values given in the following table:
Engine temp Voltage
0°C (32°F) 1V
| 20°C (68°F) 0.6V
80°C (176 °F) O.3V
N.B The above values are only approximate
|
If the readings obtained differ from the above
values, check the CO setting E7C, the tempera-
ture sensor E4 and the filament burn-off function
| E7B.
If no fault is found try fitting a known good ECU.
) 7 Check the CO value and adjust as necessary
E7C.
| Saab 900
Page 130
I
Fuel injection system 240-103
ESA Checking for idling-speed Increase
on cut-in of AC compressor
(Cars with auxiliary air valve)
Tools: Multimeter
Tachometer
1 Connect the tachometer and exhaust extrac-
tion. Start the engine and wait until it
reaches norma] temperature.
2 Press in the AC switch, whereupon a marked
drop in the engine speed should occur be-
fore it returns to normal idling speed.
3 If not:
* Check that current is available at the AC
compressor single-pin connector at the
compressor (red; RD).
e
Ms
wy f * Check the electrical system for the AC
» unit (supply to the electro-magnetic
clutch).
* Check that current is reaching the AIC
valve and that the valve is opening (see
Section 8:3, subsection 854, of the Ser-
vice Manual).
* Check that current is reaching the AC
thermostat (115 °C; 239°F).
{See Section 8:3, subsection 854, of the
Service Manual.)
* Check the yellow (GL) lead between the
AIC valve and the AC thermostat (115°C:
239 °F), and the black (SV) lead to the al-
ternator earth.
ESB Checking for idling-speed Increase
on cut-in of AC compressor
(Cars with AIC valve)
Tools: Multimeter
Tachometer
1 Connect the tachometer and exhaust extrac-
tion. Start the engine and wait until it
reaches normal temperature.
2 Depress the AC button. There should not by
any noticeable change in the engine speed.
7 1 oe
Saab 900