Distributor BMW 3 SERIES 1984 E30 Owner's Manual

5GeneralApplication
Models with carburettor or L-Jetronic fuel injection . . . . . . . . . . . . . . Transistorised Coil Ignition (TCI) system
Models with Motronic fuel injection . . . . . . . . . . . . . . . . . . . . . . . . . . Ignition functions controlled by Motronic system
Ignition coil
Primary resistance
TCI system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.82 ohms
Motronic system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.50 ohms
Secondary resistance
TCI system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8250 ohms
Motronic system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5000 to 6000 ohms
Distributor(models with TCI system)
Air gap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.3 mm to 0.7 mm
Pick-up coil/impulse generator resistance . . . . . . . . . . . . . . . . . . . . . . . 900 to 1200 ohms
Ignition timing(models with TCI system)
(Vacuum line disconnected at distributor)
316 with M10/B18 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25º BTDC at 2500 rpm (2900 rpm from 9/83)
318i with M10/B18 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30º BTDC at 3000 rpm
320i with M20/B20 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23º BTDC at 5000 ±50 rpm
518 with M10/B18 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25º BTDC at 2900 ±50 rpm
518i with M10/B18 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30º BTDC at 3000 ±50 rpm
525i with M30/B25 engine (except distributor
237 302 033) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22º BTDC at 1800 ±50 rpm
525i with M30/B25 engine (distributor 237 302 033) . . . . . . . . . . . . . . . 22º BTDC at 2150 ±50 rpm
528i with M30/B28 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22º BTDC at 2150 ±50 rpm
Chapter 5 Engine electrical systems
Air gap (TCI system) – check and adjustment . . . . . . . . . . . . . . . . . . 11
Alternator – removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Alternator brushes – check and renewal . . . . . . . . . . . . . . . . . . . . . . 17
Battery – emergency jump starting . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Battery – removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Battery cables – check and renewal . . . . . . . . . . . . . . . . . . . . . . . . . 4
Battery check and maintenance . . . . . . . . . . . . . . . . See Chapter 1
Charging system – check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Charging system – general information and precautions . . . . . . . . . 13
Distributor – removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Drivebelt check, adjustment and renewal . . . . . . . . . See Chapter 1
General information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Ignition coil – check and renewal . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Ignition sensors (Motronic system) – check and renewal . . . . . . . . . 12
Ignition system – check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Ignition system – general information and precautions . . . . . . . . . . 5
Ignition timing (TCI system) – check and adjustment . . . . . . . . . . . . 7
Impulse generator and ignition control unit – check and
renewal (TCI system) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Spark plug HT lead check and renewal . . . . . . . . . . . See Chapter 1
Spark plug renewal . . . . . . . . . . . . . . . . . . . . . . . . . . See Chapter 1
Starter motor – in-vehicle check . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Starter motor – removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . 20
Starter solenoid – removal and refitting . . . . . . . . . . . . . . . . . . . . . . 21
Starting system – general information and precautions . . . . . . . . . . 18
Voltage regulator – renewal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
5•1
Easy,suitable for
novice with little
experienceFairly easy,suitable
for beginner with
some experienceFairly difficult,
suitable for competent
DIY mechanic
Difficult,suitable for
experienced DIY
mechanicVery difficult,
suitable for expert
DIY or professional
Degrees of difficulty
Specifications Contents

5 Ignition system- general
information and precautions
The ignition system includes the ignition
switch, the battery, the distributor, the primary
(low-voltage/low-tension or LT) and
secondary (high-voltage/high-tension or HT)
wiring circuits, the spark plugs and the spark
plug leads. Models fitted with a carburettor or
L-Jetronic fuel injection are equipped with a
Transistorised Coil Ignition (TCI) system.
Models fitted with the Motronic fuel injection
system have the ignition system incorporated
within the Motronic system (Digital Motor
Electronics or DME).
Transistorised Coil Ignition (TCI)
system
This system is has four major components;
the impulse generator, the ignition control
unit, the coil, and the spark plugs. The
impulse generator provides a timing signal for
the ignition system. Equivalent to cam-
actuated breaker points in a standard
distributor, the impulse generator creates an
A/C voltage signal every time the trigger
wheel tabs pass the impulse generator tabs.
When the ignition control unit (capacitive
discharge unit) receives the voltage signal, it
triggers a spark discharge from the coil by
interrupting the primary coil circuit. The
ignition dwell (coil charging time) is adjusted
by the ignition control unit for the most
intense spark. Note: The air gap (distance
between the impulse generator and trigger
wheel tabs) can be adjusted (see Section 11).
Ignition timing is mechanically adjusted
(see Section 7). A centrifugal advance unit
that consists of spring-loaded rotating
weights advances ignition timing as engine
speed increases. The vacuum advance
adjusts ignition timing to compensate for
changes in engine load.
Motronic ignition system
This system, also known as Digital Motor
Electronics (DME), incorporates all ignition
and fuel injection functions into one central
control unit or ECU (computer). The ignition
timing is based on inputs the ECU receives for
engine load, engine speed, coolant
temperature and intake air temperature. The
only function the distributor performs is the
distribution of the high voltage signal to the
individual spark plugs. The distributor is
attached directly to the cylinder head. There is
no mechanical spark advance system used on
these systems.
Ignition timing is electronically-controlled,
and is not adjustable on Motronic systems.
During starting, a crankshaft position sensor
(reference sensor) relays the crankshaft
position to the ECU, and an initial baseline
ignition point is determined. Once the engineis running, the ignition timing is continually
changing, based on the various input signals
to the ECU. Engine speed is signalled by a
speed sensor. Early Motronic systems have
the position reference sensor and the speed
sensor mounted on the bellhousing over the
flywheel on the left-hand side. Later Motronic
systems have a single sensor (pulse sensor)
mounted over the crankshaft pulley. This
sensor functions as a speed sensor as well as
a position reference sensor. Refer to Sec-
tion 12 for checking and renewing the ignition
sensors. Note: Some models are equipped
with a TDC sensor mounted on the front of the
engine. This sensor is strictly for the BMW
service test unit, and it is not part of the
Motronic ignition system.
Precautions
Certain precautions must be observed
when working on a transistorised ignition
system.
a) Do not disconnect the battery cables
when the engine is running
b) Make sure the ignition control unit (TCI
ignition system) is always well earthed
(see Section 10).
c) Keep water away from the distributor and
HT leads.
d) If a tachometer is to be connected to the
engine, always connect the tachometer
positive (+) lead to the ignition coil
negative terminal (-) and never to the
distributor.
e) Do not allow the coil terminals to be
earthed, as the impulse generator or coil
could be damaged.
f) Do not leave the ignition switch on for
more than ten minutes with the engine
off, or if the engine will not start.
6 Ignition system- check
2
Warning: Because of the high
voltage generated by the ignition
system, extreme care should be
taken whenever an operation is
performed involving ignition components.
This not only includes the impulse
generator (electronic ignition), coil,
distributor and spark plug HT leads, but
related components such as spark plug
connectors, tachometer and other test
equipment.
1If the engine turns over but will not start,
disconnect the spark plug HT lead from any
spark plug, and attach it to a calibrated spark
tester (available at most car accessory
shops).
Note:There are two different types of spark
testers. Be sure to specify electronic
(breakerless) ignition. Connect the clip on thetester to an earth point such as a metal
bracket (see illustration).
2If you are unable to obtain a calibrated
spark tester, remove the spark plug HT lead
from one of the spark plugs. Using an
insulated tool, hold the lead about a quarter-
inch from the engine block - make sure the
gap is not more than a quarter-inch, or
damage may be caused to the electronic
components.
3Crank the engine, and observe the tip of the
tester or spark plug HT lead to see if a spark
occurs. If bright-blue, well-defined sparks
occur, sufficient voltage is reaching the plugs
to fire the engine. However, the plugs
themselves may be fouled, so remove and
check them as described in Chapter 1.
4If there’s no spark, check another HT lead
in the same manner. A few sparks followed by
no spark is the same condition as no spark at
all.
5If no spark occurs, remove the distributor
cap, and check the cap and rotor as
described in Chapter 1. If moisture is present,
use a water-dispersant aerosol (or something
similar) to dry out the cap and rotor, then refit
the cap and repeat the spark test.
6If there’s still no spark, disconnect the coil
HT lead from the distributor cap, and
test this lead as described for the spark plug
leads.
7If no spark occurs, check the primary wire
connections at the coil to make sure they’re
clean and tight. Make any necessary repairs,
then repeat the check.
8If sparks do occur from the coil HT lead, the
distributor cap, rotor, plug HT lead(s) or spark
plug(s) may be defective. If there’s still no
spark, the coil-to-cap HT lead may be
defective. If a substitute lead doesn’t make
any difference, check the ignition coil (see
Section 9). Note:Refer to Sections 10 and 11
for more test procedures on the distributors
fitted with the TCI ignition system.
Engine electrical systems 5•3
6.1 To use a spark tester, simply
disconnect a spark plug HT lead, clip the
tester to a convenient earth (like a valve
cover bolt or nut) and operate the starter –
if there is enough power to fire the plug,
sparks will be visible between the
electrode tip and the tester body
5

7 Ignition timing (TCI system)-
check and adjustment
4
Warning: Keep hands, equipment
and wires well clear of the
viscous cooling fan during
adjustment of the ignition timing.
Note:This Section describes the procedure
for checking and adjusting the ignition timing
on engines fitted with the TCI system. On
engines fitted with the Motronic engine
management system, the ignition timing is
controlled by the electronic control unit, and
no adjustment is possible. The timing can be
checked using the following procedure, but no
ignition timing values were available at the
time of writing. If the timing is thought to be
incorrect, refer to a BMW dealer.
1Some special tools are required for this
procedure (see illustration). The engine must
be at normal operating temperature, and the
air conditioning (where fitted) must be
switched off. Make sure the idle speed is
correct.
2Apply the handbrake, and chock the wheels
to prevent movement of the vehicle. The
transmission must be in neutral (manual) or
Park (automatic).
3The timing marks are located on the engine
flywheel (viewed through the timing checkhole in the bellhousing) and/or on the vibration
damper on the front of the engine.
4Where applicable, disconnect the vacuum
hose from the distributor vacuum advance
unit.
5Connect a tachometer and timing light
according to the equipment manufacturer’s
instructions (an inductive pick-up timing light
is preferred). Generally, the power leads for
the timing light are attached to the battery
terminals, and the pick-up lead is attached to
the No 1 spark plug HT lead. The No 1 spark
plug is the one at the front of the engine.
Caution: If an inductive pick-up
timing light isn’t available, don’t
puncture the spark plug HT lead
to attach the timing light pick-up
lead. Instead, use an adapter between the
spark plug and HT lead. If the insulation on
the HT lead is damaged, the secondary
voltage will jump to earth at the damaged
point, and the engine will misfire.
Note:On some models, a TDC transmitter is
fitted for checking the ignition system.
However, a special BMW tester must be
connected to the diagnostic socket to use it,
so unless the special tester is available, a
conventional timing light should be used. The
ignition timing mark may be on the vibration
damper, but if not, normally the TDC mark will
be. If the timing light is of the adjustable delay
type, then the ignition timing may be
determined by zeroing the adjustment, then
turning the adjustment until the TDC marks are
aligned, and then reading off the amount of
advance from the timing light. If a standard
timing light is being used, make a mark on the
vibration damper in accordance with the
specified advance, using the following formula
to calculate the distance from the TDC mark
to the timing mark:
Distance = 2Pr x advance
360
where P = 3.142
r = radius of vibration damper
advance = specified advance
BTDC in degrees
6With the ignition off, loosen the distributor
clamp nut just enough to allow the distributor
to pivot without any slipping.7Make sure the timing light wires are routed
away from the drivebelts and fan, then start
the engine.
8Raise the engine rpm to the specified
speed, and then point the flashing timing light
at the timing marks - be very careful of moving
engine components.
9The mark on the flywheel or vibration
damper will appear stationary. If it’s aligned
with the specified point on the bellhousing or
engine front cover, the ignition timing is
correct (see illustrations).
10If the marks aren’t aligned, adjustment is
required. Turn the distributor very slowly until
the marks are aligned, taking care not to
touch the HT leads.
11Tighten the nut on the distributor clamp,
and recheck the timing.
12Switch off the engine, and remove the
timing light and tachometer. Reconnect the
vacuum hose where applicable.
8 Distributor-
removal and refitting
4
TCI system
Removal
1After carefully marking them for position,
remove the coil HT lead and spark plug HT
leads from the distributor cap (see Chapter 1).
2Remove No 1 spark plug (the one nearest
you when you are standing in front of the
engine).
3Manually rotate the engine to Top Dead
Centre (TDC) on the compression stroke for
No 1 piston (see Chapter 2A)
4Carefully mark the vacuum hoses, if more
than one is present on your distributor.
5Disconnect the vacuum hose(s).
6Disconnect the primary circuit wires from
the distributor.
7Mark the relationship of the rotor tip to the
distributor housing (see illustration). Also
mark the relationship of the distributor
housing to the engine.
5•4 Engine electrical systems
7.1 Tools for checking and adjusting the
ignition timing
1Vacuum plugs- Vacuum hoses will, in
most cases, have to be disconnected and
plugged. Moulded plugs in various shapes
and sizes can be used for this, if wished
2Inductive pick-up timing light- Flashes a
bright, concentrated beam of light when
No 1 spark plug fires. Connect the leads
according to the instructions supplied with
the light
3Distributor spanner - On some models,
the hold-down bolt for the distributor is
difficult to reach and turn with conventional
spanners or sockets. A special spanner like
this must be used
7.9a Flywheel “OT” timing mark 7.9b Flywheel “OZ” timing mark

8Remove the hold-down nut or bolt and
clamp.
9Remove the distributor. Note:Do not rotate
the engine with the distributor out.
Refitting
10Before refitting the distributor, make
certain No 1 piston is still at TDC on the
compression stroke.
11Insert the distributor into the engine, with
the adjusting clamp centred over the hold-
down hole. Make allowance for the gear to
turn as the distributor is inserted.
12Refit the hold-down nut or bolt. The marks
previously made on the distributor housing,
and on the rotor and engine, should line up
before the nut or bolt is tightened.
13Refit the distributor cap.
14Connect the wiring for the distributor.
15Reconnect the spark plug HT leads.
16Reconnect the vacuum hoses as
previously marked.
17Check the ignition timing (see Section 7).
Motronic system
Removal
18Remove the cover from the distributor
(see illustration)and remove the distributor
cap (see Chapter 1).
19Using a small Allen key, remove the three
screws from the rotor (see illustration).
20Remove the rotor.
Refitting
21Refitting is the reverse of removal.
9 Ignition coil -
check and renewal
2
Caution: Do not earth the coil, as
the coil and/or impulse generator
could be damaged.
Note:On models equipped with the Motronic
system, a faulty ECU can cause the ignition
coil to become damaged. Be sure to test the
ignition coil if the engine will not start and an
ECU fault is suspected.
1Mark the wires and terminals for position,
then remove the primary circuit wires and the
HT lead from the coil.2Remove the coil assembly from its
mounting, then clean the outer casing and
check it for cracks and other damage.
3Inspect the coil primary terminals and the
coil tower terminal for corrosion. Clean them
with a wire brush if any corrosion is found.
4Check the coil primary resistance by
attaching an ohmmeter to the primary
terminals (see illustrations). Compare the
measured resistance to the Specifications
listed in this Chapter.
5Check the coil secondary resistance by
connecting one of the ohmmeter leads to one
of the primary terminals, and the other
ohmmeter lead to the coil high-tension
terminal (see illustrations). On TCI systems,
Engine electrical systems 5•5
8.19 Remove the rotor screws (arrowed)
with an Allen key, and pull the rotor off the
shaft8.18 Remove the three bolts (arrowed)
from the distributor cap8.7 Mark the relationship of the rotor to
the distributor housing (arrowed)
9.5b Using an ohmmeter, measure the
secondary resistance of the coil (later
Motronic system)9.5a Using an ohmmeter, measure the
secondary resistance of the coil (TCI
system)
9.4b Some Motronic systems use a
different type of coil. First, remove the coil
cover and . . .9.4a Using an ohmmeter, measure the
resistance between the primary terminals
of the ignition coil (TCI system shown)
9.4c . . . using an ohmmeter, measure the
resistance between the primary terminals
of the coil
5

connect the ohmmeter to coil terminal 1 (-)
and the centre tower. On Motronic systems,
connect the ohmmeter to coil terminal 15 (+)
and the centre tower. Compare the measured
resistance with the values given in the Specifi-
cations in this Chapter.
6If the measured resistances are not close to
those specified, the coil is defective and
should be renewed. Note that the measured
resistance will vary according to the
temperature of the coil, so don’t rush to
condemn the coil if the resistance is only a
little way out.
7It is essential for proper ignition system
operation that all coil terminals and wire leads
be kept clean and dry.
8Refit the coil in its mounting, and reconnect
the wiring. Refitting is the reverse of removal.
10 Impulse generator and
ignition control unit- check
and renewal (TCI system)
3
1The impulse generator (located in the
distributor) and ignition control unit need to be
tested in the event there is no spark at the
spark plugs. Make sure the plug leads,
ignition coil and spark plugs are working
properly (see Sections 6 and 9). There are two
types of control units; Bosch or
Siemens/Telefunken. The two types (see
illustration)can be distinguished by their
electrical connectors. The Bosch type uses a
single, large rectangular connector at the
bottom of the unit, while the
Siemens/Telefunken control unit uses two
round electrical connectors at the front of the
unit.
Check
Voltage supply and earth to ignition
control unit
2With the ignition off, remove the harness
connectors from the ignition control unit (see
illustrations). Connect a voltmeter between
connector terminals 2 and 4 on Bosch
systems, or between terminals 6 and 3 on
Siemens/Telefunken systems.
3Turn the ignition on. There should be
battery voltage on the designated terminals. If
there is no voltage, check the wiring harness
for an open-circuit (see Chapter 12).
4Using an ohmmeter, check for continuity
between connector terminal 2 (Bosch) or 6
(Siemens/Telefunken) and the earth to the
vehicle body. Continuity should exist.
5Using an ohmmeter, check for continuity
between connector terminal 4 (Bosch) or 3
(Siemens/Telefunken) and terminal 15 of the
ignition coil. Continuity should exist.
6If the readings are incorrect, repair the
wiring harness.
Impulse generator signal
7If the ignition control unit is receiving
battery voltage, check the A/C signal voltage
coming from the impulse generator to the
control unit.
5•6 Engine electrical systems
10.2b Check for voltage at terminals 6 and
3 on the control unit electrical connector
(Siemens/Telefunken system shown)10.2a Check for voltage at terminals 2 and
4 on the control unit electrical connector
(Bosch system shown)
1 Coil HT lead
2 Ignition coil
3 Spark plug HT lead
4 Spark plug
5 Ignition control unit (Bosch)
6 Ignition control unit
(Siemens/Telefunken)
7 Wiring harness8 Distributor housing with
centrifugal advance
counterweights
9 Vacuum diaphragm
10 Circlip
11 Impulse generator
12 Trigger wheel
13 Circlip
14 Dust shield15 Ignition rotor
16 Distributor
17 Roll pin
18 Trigger wheel and impulse
generator tabs
19 Cap retaining clip
20 Impulse generator
connector
10.1 Schematic of the ignition components used on engines with the TCI system

8Use a digital voltmeter for the following
tests:
a) On Bosch systems, connect the positive
probe to connector terminal 5, and the
negative probe to terminal 6 (see
illustration).
b) On Siemens/Telefunken systems, connect
the positive probe to terminal (+) of the
smaller connector, and the negative
probe to terminal (-).
9Have an assistant crank the engine over,
and check that there is 1 to 2 volts A/C
present. If there is no voltage, check the
wiring harness between the impulse generator
(in the distributor) and the control unit. If the
harness is OK, check the impulse generator
resistance.
Warning: Do not crank the
engine over for an excessive
length of time. If necessary,
disconnect the cold start injector
electrical connector (see Chapter 4) to
stop the flow of fuel into the engine.
10To check the resistance in the impulse
generator, proceed as described for your
system below:
a) On Bosch units, measure the resistance
between connector terminals 5 and 6
(see illustration 10.8). The reading
should be 1000 to 1200 ohms.
b) On Siemens/Telefunken units, measure
the resistance between the terminals of
the smaller connector. The reading should
be 1000 to 1200 ohms.
11If the resistance readings are incorrect,
renew the impulse generator. If the resistance
readings for the impulse generator are correct
and the control unit voltages (supply voltage
[paragraphs 1 to 6] and signal voltage
[paragraphs 7 to 9]) are incorrect, renew the
control unit.
Renewal
Ignition control unit
12Make sure the ignition is switched off.
13Disconnect the electrical connector(s)
from the control unit.
14Remove the mounting screws from the
control unit, and lift it from the engine
compartment.15Refitting is the reverse of removal. Note:
On Bosch control units, a special dielectric
grease is used between the heat sink and the
back of the control unit. In the event the two
are separated (renewal or testing) the old
grease must be removed, and the heat sink
cleaned off using 180-grit sandpaper. Apply
Curil K2 (Bosch part number 81 22 9 243). A
silicon dielectric compound can be used as a
substitute. This treatment is very important for
the long life of these expensive ignition parts.
Impulse generator
Caution: If the radio in your
vehicle is equipped with an anti-
theft system, make sure you
have the correct activation code
before disconnecting the battery. Refer to
the information on page 0-7 at the front of
this manual before detaching the cable.
Note: If, after connecting the battery, the
wrong language appears on the instrument
panel display, refer to page 0-7 for the
language resetting procedure.
16Disconnect the battery negative cable.
17Remove the distributor from the engine
(see Section 8).
18Using a pair of circlip pliers, remove the
circlip retaining the trigger wheel (see
illustration).
19Use two flat-bladed screwdrivers
positioned at opposite sides of the trigger
wheel, and carefully prise it up (see
illustration). Note: Push the screwdrivers in
as far as possible without bending the trigger
wheel. Prise only on the strongest, centre
portion of the trigger wheel. In the event the
trigger wheel is bent, it must be replaced with
a new one. Note:Be sure not to lose the roll
pin when lifting out the trigger wheel.
20Remove the mounting screws from the
impulse generator electrical connector, the
vacuum diaphragm and the baseplate.
21Remove the two screws from the vacuum
advance unit, and separate it from the
distributor by moving the assembly down
while unhooking it from the baseplate pin.
22Use circlip pliers to remove the circlip that
retains the impulse generator and the
baseplate assembly.
23Carefully remove the impulse generator
and the baseplate assembly as a single unit.24Remove the three screws, and separate
the baseplate assembly from the impulse
generator.
25Refitting is the reverse of removal. Note:
Be sure to position the insulating ring between
the generator coil and the baseplate. It must
be centred before tightening the mounting
screws. Also, it will be necessary to
check/adjust the air gap if the trigger wheel
has been removed, or tampered with to the
point that the clearance is incorrect (see
Section 11).
11 Air gap (TCI system)-
check and adjustment
2
Caution: If the radio in your
vehicle is equipped with an anti-
theft system, make sure you
have the correct activation code
before disconnecting the battery. Refer to
the information on page 0-7 at the front of
this manual before detaching the cable.
Note: If, after connecting the battery, the
wrong language appears on the instrument
panel display, refer to page 0-7 for the
language resetting procedure.
1Disconnect the battery negative cable.
2Insert a brass feeler gauge between the
trigger wheel tab and the impulse generator
(see illustration). Slide the feeler gauge up
Engine electrical systems 5•7
10.19 Carefully prise the trigger wheel off
the distributor shaft10.18 Use circlip pliers and remove the
circlip from the distributor shaft10.8 Back-probe the ignition control unit
connector, and check for signal voltage on
terminals 5 and 6 (Bosch system shown). It
is very helpful to use angled probes
11.2 Use a brass feeler gauge to check
the air gap (be sure the gauge rubs lightly
against the trigger wheel as well as the
locating pin for the correct adjustment)
5

and down - you should feel a slight drag on
the feeler gauge as it is moved if the gap is
correct. The gap must be as given in this
Chapter’s Specifications.
3To adjust the gap, it is necessary to remove
the impulse generator and the baseplate
assembly from the distributor (see illus-
tration 10.1).
4Follow paragraphs 17 to 24 in Section 10
and loosen the screws that retain the impulse
generator to the baseplate assembly.
5Carefully insert the feeler gauge and tighten
the screws.
6Refit the assembly back into the distributor
and recheck the adjustment.12 Ignition sensors (Motronic
system)- check and renewal
2
Note:Some models are equipped with a TDC
sensor mounted on the front of the engine.
This sensor is strictly for the BMW service test
unit, and is not part of the Motronic ignition
system.
Speed and position sensors
Check
1Locate the two electrical connectors for the
sensors (see illustrations). The grey
connector is for the position sensor, and the
white connector is for the speed sensor.
2Using an ohmmeter, check the resistance
between terminal 1 (yellow wire) and terminal
2 (black wire) on the sensor side of each
connector. The resistance should be 860 to
1,060 ohms.
3Also check the resistance between terminal
3 and either terminal 1 or terminal 2. The
resistance should be approximately 100 000
ohms.
4If the reading(s) are incorrect, renew the
sensor(s).
Renewal
5Remove the sensor mounting screw(s),using an Allen key where necessary, and pull
the sensor(s) from the sockets. Disconnect
the wiring from one sensor at a time - be sure
the connectors are not interchanged when
fitting new sensors. The bellhousing is marked
with a B for the position sensor (grey
connector) and D for the speed sensor (black
connector) (see illustration). Note: It is a
good idea to check the condition of the raised
pin on the flywheel while the sensors are out
of the sockets. Turn the engine by hand as
necessary to bring the pin into view.
6Tighten the sensor mounting screw(s)
securely, but be careful not to overtighten.
Pulse sensor (later models)
Check
7Locate the two electrical connectors for the
sensor (see illustrations). Disconnect the
electrical connector from the front.
8Using an ohmmeter, check resistance
between terminal 1 (yellow wire) and terminal
2 (black wire) on the sensor side of each
connector (see illustration). The resistance
should be 500 to 600 ohms.
9If the reading is incorrect, renew the sensor.
Renewal
10Remove the pulse sensor mounting bolt
using a 5 mm hex spanner (see illustration).
5•8 Engine electrical systems
12.10 The pulse sensor itself (arrowed) is
located on the timing belt cover, to one
side of the pulley (later models)12.8 The resistance of the pulse sensor
should be 500 to 600 ohms (later models)12.7b On later 5-Series models, the pulse
sensor connector (arrowed) is located next
to the valve cover
12.7a On later 3-Series models, the pulse
sensor connector (arrowed) is located next
to the 20-pin diagnostic connector
12.5 Location of the position sensor (B) and
speed sensor (D) on the bellhousing on all
Motronic systems – do not interchange the
sensors, or the engine will not start12.1b Location of the position sensor
(grey connector) (A) and the speed sensor
(black connector) (B) on Motronic systems
(later models)12.1a Location of the position sensor (grey
connector) (A) and the speed sensor (black
connector) (B) on Motronic systems (early
models)

when the transmission selector lever is in Park
or Neutral.
Always detach the battery negative cable
before working on the starting system.
19 Starter motor-
in-vehicle check
2
Note:Before diagnosing starter problems,
make sure the battery is fully charged.
1If the starter motor does not turn at all when
the switch is operated, make sure that the
gear lever is in Neutral or Park (automatic
transmission) or, where applicable, that the
clutch pedal is depressed (manual
transmission).
2Make sure that the battery is charged, and
that all cables, both at the battery and starter
solenoid terminals, are clean and secure.
3If the starter motor spins but the engine is
not cranking, the overrun clutch in the starter
motor is slipping, and the starter motor must
be renewed.
4If, when the switch is actuated, the starter
motor does not operate at all but the solenoid
clicks, then the problem lies either in the
battery, the main solenoid contacts, or the
starter motor itself (or the engine is seized).
5If the solenoid plunger cannot be heard
when the switch is actuated, the battery is
faulty, the switch is defective, the fusible link
is burned-out (the circuit is open), or the
solenoid itself is defective.
6To check the solenoid, connect a jumper
lead between the battery (+) and the ignition
switch wire terminal (the small terminal) on the
solenoid. If the starter motor now operates,
the solenoid is OK and the problem is in the
ignition switch, starter inhibitor switch
(automatic transmission models), clutch
switch (some manual transmission models), or
the wiring.
7If the starter motor still does not operate,
remove the starter/solenoid assembly for
dismantling, testing and repair.
8If the starter motor cranks the engine at an
abnormally-slow speed, first make sure that
the battery is charged, and that all terminal
connections are tight. If the engine is partially-
seized, or has the wrong viscosity oil in it, it
will crank slowly.
9Run the engine until normal operating
temperature is reached, then disconnect the
coil HT lead from the distributor cap and earth
it on the engine.
10Connect a voltmeter positive lead to the
battery positive post, and connect the
negative lead to the negative post.11Crank the engine, and take the voltmeter
readings as soon as a steady figure is
indicated. Do not allow the starter motor to
turn for more than 10 seconds at a time. A
reading of 9 volts or more, with the starter
motor turning at normal cranking speed, is
normal. If the reading is 9 volts or more but
the cranking speed is slow, the solenoid
contacts are burned, there is a bad
connection, or the starter motor itself is faulty.
If the reading is less than 9 volts and the
cranking speed is slow, the starter motor is
faulty or the battery is responsible (defective
or discharged).
20 Starter motor-
removal and refitting
1
Note:If the starter motor is defective, it should
be renewed, or taken to an auto electrical
specialist for repair. Overhaul of the starter
motor is unlikely to be a practical proposition
for the home mechanic, even if spare parts are
available. However, the solenoid can be
renewed separately (see Section 21).
Removal
Caution: If the radio in your
vehicle is equipped with an anti-
theft system, make sure you
have the correct activation code
before disconnecting the battery. Refer to
the information on page 0-7 at the front of
this manual before detaching the cable.
Note: If, after connecting the battery, the
wrong language appears on the instrument
panel display, refer to page 0-7 for the
language resetting procedure.
1Detach the battery negative cable.
2Raise the vehicle and support it securely on
axle stands.
3Clearly label the wires from the terminals onthe starter motor and solenoid, then
disconnect them. Note: On some models, it
may be necessary to remove the air cleaner
(see Chapter 4), coolant expansion tank (see
Chapter 3) and the heater hoses to gain
access to the top of the starter. Carefully label
any hoses or components that need to be
removed from the engine compartment, to
avoid confusion when reassembling.
4Unscrew the mounting bolts and detach the
starter (see illustrations).
Refitting
5Refitting is the reverse of removal.
21 Starter solenoid-
removal and refitting
1
Removal
Caution: If the radio in your
vehicle is equipped with an anti-
theft system, make sure you
have the correct activation code
before disconnecting the battery. Refer to
the information on page 0-7 at the front of
this manual before detaching the cable.
Note: If, after connecting the battery, the
wrong language appears on the instrument
panel display, refer to page 0-7 for the
language resetting procedure.
1Disconnect the battery negative cable.
2Remove the starter motor (see Section 20).
3Disconnect the cable from the solenoid to
the starter motor terminal.
4Remove the screws which secure the
solenoid to the starter motor.
5Detach the solenoid from the starter body.
6Remove the plunger and plunger spring.
Refitting
7Refitting is the reverse of removal.
5•12 Engine electrical systems
20.4b Withdrawing the starter motor from
the M40 engine20.4a Working under the vehicle, remove
the starter lower mounting bolt and nut
(arrowed)

12
Chapter 12 Body electrical systems
Bulb renewal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Central locking system - description and check . . . . . . . . . . . . . . . . 20
Cruise control system - description and check . . . . . . . . . . . . . . . . 19
Direction indicator/hazard warning flasher - check and renewal . . . 5
Electric windows - description and check . . . . . . . . . . . . . . . . . . . . 21
Electrical system fault finding - general information . . . . . . . . . . . . . 2
Fuses - general information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
General information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Headlight housing - removal and refitting . . . . . . . . . . . . . . . . . . . . . 14
Headlights - adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Headlights - bulb renewal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Heated rear window - check and repair . . . . . . . . . . . . . . . . . . . . . . 17
Ignition switch - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . 7
Instrument cluster - removal and refitting . . . . . . . . . . . . . . . . . . . . . 10
Radio - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Radio aerial - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Relays - general information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Service Indicator (SI) board - general information . . . . . . . . . . . . . . 11
Steering column switches - removal and refitting . . . . . . . . . . . . . . . 6
Supplemental Restraint System (SRS) - general information . . . . . . 18
Windscreen/tailgate wiper motor - removal and refitting . . . . . . . . . 16
Wiring diagrams - general information . . . . . . . . . . . . . . . . . . . . . . . 22
12•1
Easy,suitable for
novice with little
experienceFairly easy,suitable
for beginner with
some experienceFairly difficult,
suitable for competent
DIY mechanic
Difficult,suitable for
experienced DIY
mechanicVery difficult,
suitable for expert
DIY or professional
Degrees of difficulty Contents
1 General information
The chassis electrical system of this vehicle
is of 12-volt, negative earth type. Power for
the lights and all electrical accessories is
supplied by a lead/acid-type battery, which is
charged by the alternator.
This Chapter covers repair and service
procedures for various chassis (non-engine
related) electrical components. For
information regarding the engine electrical
system components (battery, alternator,
distributor and starter motor), see Chapter 5.
Warning: To prevent electrical
short-circuits, fires and injury,
always disconnect the battery
negative terminal before
checking, repairing or renewing electrical
components.
Caution: If the radio in your
vehicle is equipped with an anti-
theft system, make sure you have
the correct activation code
before disconnecting the battery, Refer to
the information on page 0-7 at the front of
this manual before detaching the cable.
Note: If, after connecting the battery, the
wrong language appears on the instrument
panel display, refer to page 0-7 for the
language resetting procedure.
2 Electrical system fault
finding- general information
2
A typical electrical circuit consists of an
electrical component, any switches, relays,
motors, fuses, fusible links or circuit breakers,
etc related to that component, and the wiring
and connectors that link the components to
both the battery and the chassis. To help you
pinpoint an electrical circuit problem, wiring
diagrams are included at the end of this book.
Before tackling any troublesome electrical
circuit, first study the appropriate wiring
diagrams to get a complete understanding of
what makes up that individual circuit.
Troublespots, for instance, can often be
isolated by noting if other components related
to that circuit are routed through the same
fuse and earth connections.
Electrical problems usually stem from
simple causes such as loose or corroded
connectors, a blown fuse, a melted fusible
link, or a bad relay. Inspect all fuses, wires
and connectors in a problem circuit first.
The basic tools needed include a circuit
tester, a high-impedance digital voltmeter, a
continuity tester and a jumper wire with an in-
line circuit breaker for bypassing electrical
components. Before attempting to locate or
define a problem with electrical testinstruments, use the wiring diagrams to
decide where to make the necessary
connections.
Voltage checks
Perform a voltage check first when a circuit
is not functioning properly. Connect one lead
of a circuit tester to either the negative battery
terminal or a known good earth.
Connect the other lead to a connector in
the circuit being tested, preferably nearest to
the battery or fuse. If the bulb of the tester
lights up, voltage is present, which means that
the part of the circuit between the connector
and the battery is problem-free. Continue
checking the rest of the circuit in the same
fashion.
When you reach a point at which no voltage
is present, the problem lies between that point
and the last test point with voltage. Most of
the time, problems can be traced to a loose
connection.Note:Keep in mind that some
circuits receive voltage only when the ignition
key is turned to a certain position.
Electrical fault diagnosis is simple if you
keep in mind that all electrical circuits are
basically electricity running from the battery,
through the wires, switches, relays, fuses and
fusible links to each electrical component
(light bulb, motor, etc) and then to earth, from
where it is passed back to the battery. Any
electrical problem is an interruption in the flow
of electricity to and from the battery.

REF•10Fault Finding
Engine will not rotate when attempting to start
m mBattery terminal connections loose or corroded (Chapter 1).
m mBattery discharged or faulty (Chapter 1).
m mAutomatic transmission not completely engaged in Park (Chap-
ter 7B) or (on models with a clutch switch) clutch not completely
depressed (Chapter 8).
m mBroken, loose or disconnected wiring in the starting circuit
(Chapters 5 and 12).
m mStarter motor pinion jammed in flywheel ring gear (Chapter 5).
m mStarter solenoid faulty (Chapter 5).
m mStarter motor faulty (Chapter 5).
m mIgnition switch faulty (Chapter 12).
m mStarter pinion or flywheel teeth worn or broken (Chapter 5).
m mEngine internal problem (Chapter 2B).
Engine rotates, but will not start
m
mFuel tank empty.
m mBattery discharged (engine rotates slowly) (Chapter 5).
m mBattery terminal connections loose or corroded (Chapter 1).
m mLeaking fuel injector(s), faulty fuel pump, pressure regulator, etc
(Chapter 4).
m mFuel not reaching fuel injection system or carburettor (Chapter 4).
m mIgnition components damp or damaged (Chapter 5).
m mFuel injector stuck open (Chapter 4).
m mWorn, faulty or incorrectly-gapped spark plugs (Chapter 1).
m mBroken, loose or disconnected wiring in the starting circuit
(Chapter 5).
m mLoose distributor mounting bolts causing ignition timing to wander
(Chapters 1 and 5).
m mBroken, loose or disconnected wires at the ignition coil, or faulty
coil (Chapter 5).
Engine hard to start when cold
m mBattery discharged (Chapter 1).
m mFuel system malfunctioning (Chapter 4).
m mInjector(s) leaking or carburettor automatic choke faulty (Chap-
ter 4).
m mDistributor rotor carbon-tracked (Chapter 5).
Engine hard to start when hot
m
mAir filter element clogged (Chapter 1).
m mFuel not reaching the fuel injection system or carburettor (Chap-
ter 4).
m mCorroded battery connections, especially earth (negative)
connection (Chapter 1).
Starter motor noisy or excessively-rough in
engagement
m mPinion or flywheel gear teeth worn or broken (Chapter 5).
m mStarter motor mounting bolts loose or missing (Chapter 5).
Engine starts, but stops immediately
m
mLoose or faulty electrical connections at distributor, coil or
alternator (Chapter 5).
m mInsufficient fuel reaching the fuel injector(s) or carburettor
(Chapters 1 and 4).
m mDamaged fuel injection system speed sensors (Chapter 5).
m mFaulty fuel injection relays (Chapter 5).
Oil puddle under engine
m
mOil sump gasket and/or sump drain plug seal leaking (Chapter 2).
m mOil pressure sender unit leaking (Chapter 2).
m mValve cover gaskets leaking (Chapter 2).
m mEngine oil seals leaking (Chapter 2).
Engine idles erratically
m
mVacuum leakage (Chapter 4).
m mAir filter element clogged (Chapter 1).
m mFuel pump not delivering sufficient fuel to the fuel injection system
or carburettor (Chapter 4).
m mLeaking head gasket (Chapter 2).
m mTiming belt/chain and/or sprockets worn (Chapter 2).
m mCamshaft lobes worn (Chapter 2).
m mFaulty charcoal canister, where fitted (Chapter 6). This Section provides an easy-reference guide to the more
common problems which may occur during the operation of your
vehicle. These problems and their possible causes are grouped under
headings denoting various components or systems, such as Engine,
Cooling system, etc. They also refer you to the Chapter and/or
Section which deals with the problem.
Remember that successful fault diagnosis is not a mysterious
black art practised only by professional mechanics. It is simply the
result of the right knowledge combined with an intelligent, systematic
approach to the problem. Always work by a process of elimination,
starting with the simplest solution and working through to the mostcomplex - and never overlook the obvious. Anyone can run the fuel
tank dry or leave the lights on overnight, so don’t assume that you are
exempt from such oversights.
Finally, always establish a clear idea of why a problem has
occurred, and take steps to ensure that it doesn’t happen again. If the
electrical system fails because of a poor connection, check all other
connections in the system to make sure that they don’t fail as well. If a
particular fuse continues to blow, find out why - don’t just renew one
fuse after another. Remember, failure of a small component can often
be indicative of potential failure or incorrect functioning of a more
important component or system.
Engine