Page 41
- .~
BREAKERLESS
IGNITION
,
"*
SYSTEM
This system differs from conventional ignition systems as
follows.
The breaker points in the distributor have been replaced
by a transmission unit comprising an impulse transmitter,
"
-,
S 6245
an induction coil and a rotor disc. The impulse transmitter
is connected to an electronic control unit in which the
signal from the distributor is converted and ampl ified.
The electronic control unit is connected to the ignition
coil which is a high-voltage coil that has been specially
adapted to the system.
~~------------------------------------------------------,
2
15
~1----1-~:~--~~
I
S 6306
BREAKERLESS IGNITION SYSTEM
1. Battery
2. Ignition switch
3. Electronic control unit
4. Compensating resistor
5. Distributor
6. Ignition coil
7. Screened cable
8. To fuel pump relay, tachometer and TSI socket
9. To relay terminal 87a (connected at start)
.;- .
ELECTRONIC CONTROL UNIT
Nov. 1977
COMPENSATING RESISTOR
340-1
Page 42
Operating principle
Block diagram to illustrate operating principle
In the input stage, which is designed in the form of a
A sinusoidal control voltage is present in the induction coil, .
which alternates rapidly between positive and negative polarity. This alternation in polarity is util ized to transmit
pulses. The pulse transmitted is governed by the engine
speed and varies between 0.3 V and 100 V. The signal is
then converted and amplified in the electronic control
unit. When the sinusoidal voltage passesthrough zero,
the ignition voltage is induced in the secondary circuit of
Schmitt trigger, the sinusoidal signal from the distributor
is amp Iified and converted to a rectangular pulse. The
regulation of the dwell angle adapts the time of the current flow through the output transistor and the ignition
coil to the engine speed. In contrast to the constant dwell
angle in a conventional ignition system, the electronic
system increases the dwell angle with increasing/engine
speed, thereby providing a high ignition voltage even at
high engine speed. At the driver, the signal is amplified
once again and proceeds to the Darlington output stage.
Current now flows through the primary circuit of the
ignition coil.
the coil (when the rotor poles are in line with the stator
poles).
This corresponds to the breaking of the points in a conventional ignition system.
At the moment of ignition, which occurs when the sinusoidal signal passesthrough zero, the ignition voltage is induced in the secondary circuit of the coil.
To relay, terminal
Compensating
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resistor
.
I-
Compensating
resistor
-
-
To distributor
87a
--
.
-
Ignition
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coil
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Stabil ization
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I mpulse transmitter
in distributor
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Trigger
Dwell angle
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Driver
Darlington
output
stage.
control
1
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S 5902
BLOCK
DIAGRAM
Nov. 1977
Page 43
IGNITION
COIL AND COMPENSATING
RESISTOR
The ignition coil has been specially designed for this ignition system and provides a voltage about 30 % higher
than the coil in a conventional
system.
The compensating
resistor is designed to limit the primary
current at low engine speeds.
The compensating
resistor is mounted on the right-hand
wheel housing, underneath
the electronic control unit
-,
bracket.
IGNITION
COIL
WARNING
The high tension lead between the ignition coil and
the distributor
should be equipped with a special
safety harness to prevent it rubbing and wearing
against the turbo pipe.
f
1
I
Nov. 1977
341-1
Page 44
DISTRIBUTOR
Electronic control unit
The size and shape of the distributor are the same as
those of a conventional one. The distributor also has centrifugal and vacuum control of the ignition timing.
The electrical transmission unit is similar to a generator.
The rotor reverses the direction of the magnetic field
built up by the permanent magnet. The change in the
magnetic field is governed by the clearance between the
rotor and the stator. Since the rotor has the same number
of poles as the stator, a mean value of the gap between
the poles on the rotor and those on the stator is achieved,
which guarantees correct timing even if there is a certain
amount of play in the moving parts of the distributor.
Thus, the ignition timing is not affected by mechanical
wear since the circuit is broken electronically.
The control unit is the electronic part of the ignition system in which the pulse from the distributor is converted
and amplified. Control and regulation of the dwell angle
are automatic.
The control unit comprises a circuit board on which an
integrated circuit, transistors, condensers, diodes and
resistors are mounted.
The electronic control unit is mounted on the right-hand
wheel housing.
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ELECTRONIC CONTROL UNIT
1. Plastic cover
2. Power transistor
3. Pri nted circu it board
4. Baseplate
S 5885
DISTRIBUTOR
1. Rotor
2. Stator
3. Induction coil
4. Stator plate
5. Rotor sleeve
6. Stator sleeve
7. Outer gap
8. Magnet
9. Inner gap
10. Retaining plate and sleeve
342-1
Nov. 1977
Page 45
Changing the induction coil
7. Remove the circlip on the impulse transmitter and lift
the latter.
1. Remove the distributor.
2. Remove the distributor cap, rotor arm and condensate
trap.
3. Remove the cable contact retainer and withdraw the
contact.
4. Remove the vacuum control unit, the clip retainers
and the three screws in the impulse transmitter plate.
5. Remove the rotor circlip.
S 5889
REMOVE THE IMPULSE TRANSMITTER
REMOVING THE ROTOR CIRCLlP
8. Remove the three screws securing the induc~ion coil
to the plate .
.'
6. Lift the rotor and save the pin and the shim.
LOOSENING THE SCREWS TO THE INDUCTION COIL
Reassemble in the reverse order.
REMOVING THE ROTOR
Nov. 1977
342-2
Page 46
"
(
Distributor
degrees
. 15 ~~~~~~~~~~~~~~~~-T-T-r-r-r-r-r-r'-'-'-'-'-'-'-'-~~~~r-r-r-~~
10
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100
200
300
IGNITION ADVANCE GRAPHS, VACUUM ADVANCE
400
mmHg
5900
Distributor
degrees
0
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2000
1000
o
3000
4000
Distributor re!?301
IGNITION ADVANCE GRAPHS, CENTRIFUGAL
342-3
ADVANCE
Nov. 1977
Page 47
Some considerations of vital importance to work on the
Fault-tracing in the electronic ignition system
electronic ignition system
1. When the engine is running, dangerously high voltage
which may prove fatal may be present in the primary
circuit of the coil and in all cables connected to terminal 1. This is because the spark energy in the system
is considerably higher than in conventional ignition
systems.
2. When the ignition is switched on, full primary current
will flow through the primary circuit of the coil. Consequently, always disconnect terminal 15 on the ignition coil before commencing work with the ignition
on.
3. In conjunction with work on the screened impulse
cable between the impulse transmitter in the distributor and the control unit, strict attention must be
given to polarity. Should the polarity be reversed, a
stable basic ignition setting will not be possible and
timing and dwell will also be affected.
The recommended steps must be performed one at a
time and in the stated order. If on inspection components are found to be defective, these must be renewed
before any further fault-tracing is carried out. If a fault
is known to occur, for example, under certain temperature conditions, always attempt as far as possible to
trace faults under similar conditions. Thus, if trouble
with starting the car is experienced during cold weather,
fault-tracing should be carried out on a thoroughly cold
car. Such procedure is necessary because defective electronic components may operate perfectly under normal
temperature conditions before breaking down completely.
Bad connections can also be affected by temperature.
Fault-tracing equipment
Ignition setting instrument (preferably with a 900 dwell
angle scale); volt-ohmmeter with ~calesfor 15 V d.c.
and 5 V a.c., minimum sensitivity of 10000 ohm/V, 0-5
ohm midscale, 0-5 kohm midscale.
1. Engine completely dead, fires without starting or is
difficult
to start
CHECK
READING
CONDITION OF THE SYSTEM;
PROBABLE FAULT
CHECK AND REMEDY AS
NECESSARY
1. Turn the engine over
on the starter and
check the length of
the spark between
the high tension lead
from the coil and
More than 12 mm
Starter circuit and starter relay
probably working
Check 0.4
compensating
resistor by means of ohmmeter.
Check the ignition setting.
Check for flashover in coil isolator, distributor cap, rotor, ignition leads and plugs.
c
ground
Less than 12 mm
or no spark
Check the fuel system.
Check that current flows from
the starter relay circuit to the
connection on the compensating resistor. When the starter
is running, the voltage between
the common connection and
the + on the battery shou Id be
O. If not, check relay and wiring.
Proceed to step 2.
2. Switch on the igni-
Less than 11 V
Charge the battery; readings
taken with insufficient battery
voltage will give faulty values.
More than 11 V
Proceed to step 3.
tion. Before proceeding, check that
the battery charge
is at least 11 V.
Nov. 1977
342-4
Page 48
,
CHECK
READING
CONDITION OF THE SYSTEM;
PROBABLE FAULT
CHECK AND REMEDY As
NECESSARY
3. Measure the voltage
between terminal 15
OV
Break in compensating resistor
or leakage from terminal 15 on
ignition switch
Check compensating resistor by
means of ohmmeter. Check that
on the coil and
ground
on coil and ground
.
I
check ignition switch and wiring.
Check resistance of primary
winding (0,95-1,4 ohm)
Lessthan 6 V
Short-circuit
ing of coil
6-8 V
Primary coil winding and compensating resistor sound
Proceed to step 4.
8-12 V
Bad ground connection
Check using ohmmeter that contact pin 31 on the control unit
connector has good ground connection
12 V
Break in primary coil winding
Check using ohmmeter
(0,95-1,4 ohm)
Control unit not conducting
Check for battery voltage at contact pin 15, using voltmeter
in primary wind-
i
4. Measure the voltage
between terminal 1
voltage from the ignition switch
is present at the single terminal
on the 0.4 ohm resistor. If not,
OV
Short-circuit
0.5-2 V
Power transistor in control
unit sound
Proceed to step 5
12 V
Control unit not conducting
Change control unit. Check for
faulty insulation on cables to
terminal 16 on the control unit.
in control unit
Exchange control unit
¥
342-5
SA~
--
Nov. 1977
Page 49
CHECK
5. Measure resistance
in the secondary
coil winding
6. Connect a dwell
meter
Check dwell angle
READING
CONDITION OF THE SYSTEM;
PROBABLE FAULT
CHECK AND REMEDY AS
Defective secondary winding in
Chanqe the coil
NECESSARY
Should be
5,5-8 k ohm
coil
Appreciable deviation
Defective secondary winding in
coil
Change the coil
65-900
Control unit and impulse transmitter probably sound
Proceed to step 6
Maximum reading
on scale
Dwell meter range insufficient
(many dwell meters have maximum reading of 700) and consequently no information is
obtained
Connect a voltmeter across pins
7 and 31d of control unit cable
connector. At starting speed
(100 rev/min), a minimum reading of 1 V a.c. should be obtained. This indicates thatimpulses of sufficient strength are
being generated. If there is no
voltage or the voltage is too low,
check the screened impulse
cable. Thereafter, check the irnpulse transmitter in the distributor using on ohmmeter (8951285 ohm).Check the air gap between the rotor and the stator
and, if necessary, adjust to 0.25
mm using a non-magnetic feeler
gauge. If the fault persists,
change the impulse transmitter:.
The control unit does not
react to impulses from the
impulse transmitter
Change the control unit
_,t
2. Poor running
Poor running of the engine is unlikely to be caused by
faulty electronics.
Check the following items first:
1. Good connections throughout ignition system.
2. Ignition setting and centrifugal and vacuum advance.
3. General condition of spark plugs.
4. Rotor: check operation, insulation (burns, dirt) and
contacts.
5. Distributor cap: insulation (cracks, flashover burns,
dirt) and contacts.
6. Ignition leads.
7. Ignition coil: spark length at starting revs 12 mm
minimum; insulation (burns, dirt).
Nov. 1977
8. Connect a dwell meter and check that the dwell angle
varies with the speed as shown on the chart. At less
than 2000 rev/m in, the dwell angle is largely regulated by the control unit. At speedsgreater than 2 000
rev/min. the dwell angle is largely regulated by the
shape of the impulses from the impulse transmitter.
Thus wide deviations in the dwell angle can be traced
either to the control unit or the impulse transmitter.
Deviation of ± 100 is to be regarded as normal.
9. The fuel system.
In the case of faults occurring under extremes of temperature, the control unit may be suspected. Poor soldering
and defective components probably become most evident.
at extremes of temperature. The conventional ignition
condensor is incorporated in the control unit and may
be faulty just as frequently as in conventional ignition
systems - in other words, very rarely.
SAAB
342-6
Page 50
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