Page 61
240-22 Fuel injection system
Poor drivability during the warm-up
period
1 Check the control pressure with the engine
cold. Excessive control pressure during the
warm-up period produces a lean fuel-air mix-
ture.
2 a Check the CO-value (engine at normal
temperature).
b Check the pulse ratio (Section 2:4, sub-
section 254, of the Service Manual for
US-spec. cars).
Check the hot-start relay (see "Cold-start
valve - performance and sealing” on page
240-8).
3 Check that there is no air leaking between
the air flow sensor and the engine.
4 Check that the warm-up period for the en-
gine is normal by observing the temperature
gauge. An abnormally long warm-up period
may be caused by a faulty thermostat.
5 Check the fuel-boosting system (see section
under "Cold-start valve - performance and
sealing” on page 240-8).
Saab 900
Page 62
Fuel injection system 240-23
Poor drivability - engine at normal temp-
erature
1 a Check the CO-value (engine at normal
temperature).
b Check the pulse ratio (engine at normal
temperature) as described in Section
2:4, subsection 254, of the Service Man-
ual for US-spec. cars.
e 2 With the valve open, check the control pres-
sure (engine at normal temperature).
3 Check that there is no air leaking between
the air flow sensor and the engine.
a
Saab 900
Page 63
—
240-24 Fuel injection system
Poor performance/low top speed
1 Check that the throttle butterfly opens fully
when the pedal is fully depressed.
§ 5206
2 Check that the fuel flow is sufficient by
measuring the quantity of return fuel flowing
during a 30-second period. See under "Fuel
pump capacity”, page 240-6.
3 Check whether any parts of the air flow sen-
sor are sticking as follows:
e Run the engine to normal temperature
and then connect a CO meter.
e Switch off the engine and then restart it
without touching the accelerator. Read
off the CO value.
e Rev the engine to around 3000 r/min and
then allow it to return to idling speed. If
the CO value is different now to the earlier
reading, then either the control plunger
or the lever is sticking.
© Check that the lever moves freely.
Saab 900
Page 64
Fuel injection system 240-25
If the control plunger is binding, separate the
fuel distributor from the air flow sensor, ensuring
that the control plunger does not fall out. Extract
and inspect the control plunger (avoid handling
the sealing surfaces). Clean the plunger in pet-
rol, install it and refit the fuel distributor. Never
dismantle the fuel distributor any further.
4 a Check the CO value (engine at normal
temperature).
b Check the pulse ratio (see Section 2:4,
subsection 254, of the Service Manual
for US-spec. cars).
H-JETRONIC
TAS TVERHALTNIS £-, —
A RE GHLUNG &
. 5 Check the fuel atomization at each injection
valve. The deposits on the spark plugs can
give an indication of poor atomization.
EB _ Saab 900
Page 65
240-26 Fuel injection system
Excessive fuel consumption
41 a Check the CO value (engine at normal
temperature).
b Check the pulse ratio (engine at normal
temperature) as described in Section
2:4, subsection 254, of the Service Man-
ual for US-spec. cars.
2 Check the control pressure with the engine
hot. Insufficient control pressure results ina
rich fuel-air mixture.
3 Check the fuel atomization at each injection
valve. The deposits on the spark plugs can
give an indication of poor fuel atomization.
4 Check that the cold-start valve is not leak-
ing.
Ce ok
1
het | lias
—
b
.
5 Check that there is no external leakage of
fuel.
Saab 900
Page 66
Fuel injection system 240-27
Erratic CO value and idling speed, diffi-
culty in adjusting
1 Check that no air is leaking between the air
flow sensor and the engine.
2 Check whether any parts of the air flow sen-
sor are sticking, as follows:
¢ Run the engine to normal temperature
and then connect a CO-meter.
© Switch off the engine and then restart it
without touching the accelerator. Read
off the CO value.
e Rev the engine to around 3000 r/min and
then allow it to return to idling speed. If
the CO value is different now to the earlier
reading, then either the control plunger
or the lever is sticking.
* Check that the lever moves freely.
If the control plunger is-binding, separate the
fuel distributor from the air flow sensor, ensuring
that the control plunger does not fall out. Extract
and inspect the control plunger (avoid handling
the sealing surfaces). Clean the plunger in pet-
rol, install it and refit the fuel distributor. Never
dismantle the fuel distributor any further,
3 Check that the disc in the auxiliary air valve
is not sticking.
Saab 900
Page 67
240-28 Fuel injection system
Replacing the air cleaner filter
element
1 Remove the rubber duct from between the
air flow sensor and the throttle housing.
2 Remove the bolts securing the lower section
of the air flow sensor to the air cleaner.
3 Raise the mixture control unit slightly and re-
move the filter element. Take care not to
damage the fuel line.
4 Remove the filter element holder from the
bottom of the air cleaner and clean the air
cleaner casing.
5 Fit the cleaner element holder and the new
element.
6 Bolt the air flow sensor to the air cleaner.
7 Fit the rubber duct between the air flow sen-
sor and the throttle housing.
Mixture control unit
Removal
1 Thoroughly clean the area around the fuel
connections on the fuel distributor.
2 Disconnect the fuel lines from the fuel dis-
tributor. Disconnect the lines to the injec-
tion valves before disconnecting the control
pressure line, to avoid damaging the adja-
cent lines.
3 Remove the rubber duct from between the
air flow sensor and the throttle housing.
4 Undo the retaining bolts, and remove the
mixture control unit from the air cleaner.
Saab 900
Page 68
a Fuel injection system 240-29
Assembly
1 Make sure that the air cleaner element is in
the correct position and then bolt the mix-
ture control unit to the air cleaner.
2 Connect the fuel line to the fuel distributor.
3 Fit the rubber duct between the air flow sen-
sor and the throttle housing.
Fuel distributor
The fuel distributor must not be dismantled but
should be replaced when faulty.
When separating the fuel distributor from the air
flow sensor, ensure that the control plunger does
not fall out.
If the control plunger has been removed, it must
be thoroughly cleaned in petrol and reassem-
bled. Avoid touching the plunger sealing sur-
faces with the fingers.
When assembling the fuel distributor, ensure
that the "O" ring is located in its groove. Tighten
the three retaining bolts to a torque of 3.2-
3.8Nm (2.4-2.8 Ibf ft).
Line pressure regulator
The line pressure regulator is located inside the |
screw plug at the return line and return connec- |
tion from the warm-up regulator/boost control
circuit.
The regulator comprises the following:
1 Piston with "O” ring
2 Spring
3 Shims
4 Screw plug with "O" ring and washer. {The
screw plug contains a shut-off valve which
closes the return line from the warm-up reg- oe
ulator/boost control circuit when the fuel
pump is not operating. The socket head |
screw in the plug should not normally be re-
moved.)
Saab 900
Page 69
240-30 Fuel injection system
Lever adjustment arm and sen-
sor plate
To remove
1 Remove the mixture control unit and un-
screw the plastic lower section and fuel dis-
tributor.
2 Undo the retaining screw and remove the
sensor plate.
3 Remove the circlips from the lever pivot, fol-
lowed by the shims, seals, spring (fitted on
one side only) and the balls.
4 Undo the counterweight retaining screw and
press out the spindle.
5 Remove the lever, counterweight and ad-
justment arm.
6 Tap out the plug over the adjusting screw -
remember to refit it after setting the fuel/air
mixture.
Refer to page 240-15 for setting of the fuel/
air mixture.
To refit
1 Place the counterweight on the lever but
leave the retaining screw slack.
2 Place the adjustment arm in the lever, with
the socket head of the adjusting screw visi-
ble.
Saab 900
Page 70
Fuel injection system 240-31
3 Grease both bearings using Bosch Ft2v2 sili-
con grease or the equivalent.
4 Place the lever assembly in the air flow sen-
sor housing and fit the spindle.
5 Grease the balls with silicon grease and fit
them, followed by the spring (in the longer
bearing seating), the seals, the shims and
the circlips.
N.B.
The circlips are pressed and must be fitted with ya 3
the sharp edge facing outwards. 7
200
1 Circlip
2 Shim
3 Seal
4 Spring
5 Ball
6 Mount the sensor plate in the air venturi.
Centre the lever so that the threaded hole is
aligned with the hole in the sensor plate.
Tighten the counterweight screw.
Tightening torque:
4.7-5.2Nm (3.5 -3.8 Ibf ft)
7 Fit the sensor plate retaining screw and
tighten it. Check that the lever moves freely,
without resistance.
Tightening torque:
5.0-5.5 Nm (3.7 - 4.1 Ibf ft)
8 Adjust the rest position setting of the sensor
plate by bending the spring on the stop brac-
ket underneath the air flow sensor.
Saab 900