1986 BMW 3 SERIES Rpm

Fuel system
Idle speed
3-Series, E30
316 with M10/B18 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 850 ± 50 rpm
316i with M40/B16 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 800 ± 40 rpm
318i with M10/B18 engine (manual transmission) . . . . . . . . . . . . . 850 ± 50 rpm
318i with M10/B18 engine (automatic transmission) . . . . . . . . . . . 750 ± 50 rpm
318i with M40/B18 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 800 ± 40 rpm
320i with M20/B20 engine (L-Jetronic) . . . . . . . . . . . . . . . . . . . . . . 800 ± 50 rpm
320i with M20/B20 engine (Motronic) . . . . . . . . . . . . . . . . . . . . . . . 760 ± 40 rpm
325i with M20/B25 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 760 ± 40 rpm
5-Series, E28 (“old-shape”)
518 and 518i with M10/B18 engine . . . . . . . . . . . . . . . . . . . . . . . . 800 ± 50 rpm
All other models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 850 ± 50 rpm
5-Series, E34 (“new-shape”)
518i with M40/B18 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 800 ± 40 rpm
520i with M20/B20M engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 760 ± 40 rpm
525i with M20/B25M engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 760 ± 40 rpm
530i with M30/B30M engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 800 ± 50 rpm
535i with M30/B35M engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 850 ± 50 rpm
CO% at 3000 rpm
3-Series, E30
316 with M10/B18 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.5 to 1.0
316i and 318i with M40/B16 engine . . . . . . . . . . . . . . . . . . . . . . . . 0.7 ± 0.5
318i with M10/B18 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.0 maximum
320i with M20/B20 engine (L-Jetronic) . . . . . . . . . . . . . . . . . . . . . . 1.0 ± 0.5
320i with M20/B20 engine (Motronic) . . . . . . . . . . . . . . . . . . . . . . . 0.7 ± 0.5
325i with M20/B25 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.0 ± 0.5
5-Series, E28 (“old-shape”)
518 and 518i with M10/B18 engine . . . . . . . . . . . . . . . . . . . . . . . . 1.0 maximum
525i with M30/B25 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.0 ± 0.5
528i with M30/B28 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5 maximum
535i with M30/B34 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.3 to 1.5
M535i with M30/B34 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.3 to 1.5
5-Series, E34 (“new-shape”)
All models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.7 ± 0.5
Air filter element
M10 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Champion W155 (round) or U504 (square)
M20 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Champion U504 or U527
M30 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Champion U504 or U527
M40 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Champion U527
Fuel filter (all fuel injection engines) . . . . . . . . . . . . . . . . . . . . . . . . . . . . Champion L206
Ignition system
Spark plug type
M10, M20 and M30 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Champion N9YCC
M40 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Champion C9YCC
Spark plug gap* . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.8 mm
Spark plug (HT) leads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Champion type not available
* The spark plug gap quoted is that recommended by Champion for their specified plugs listed above. If spark plugs of any other type are to be
fitted, refer to their manufacturer’s spark plug gap recommendations.
Brakes
Disc brake pad thickness (minimum) . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.0 mm
Drum brake shoe lining thickness (minimum) . . . . . . . . . . . . . . . . . . . . . 2.0 mm
Wiper blades
Windscreen
3-Series . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Champion X-5103
3-Series passenger side from 1991 . . . . . . . . . . . . . . . . . . . . . . . . . . Champion X-5103 (20 inch) or Champion X-5303 (21 inch)
5-Series, E28 (“old-shape”) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Champion X-4503
5-Series, E34 (“new-shape”) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Champion type not available
Tailgate
3-Series . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Champion X-4503
5-Series . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Champion type not available
1•2Servicing Specifications

2A
General
Displacement
3-series, E30 body style
316i (1988 to 1991) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1596 cc (M40/4-cylinder engine)
316 (1983 to 1988) and 318i (1983 to 1987) . . . . . . . . . . . . . . . . 1766 cc (M10/4-cylinder engine)
318i (1987 1991) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1796 cc (M40/4-cylinder engine)
320i (1987 to 1991) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1990 cc (M20/6-cylinder engine)
325i (1987 to 1991) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2494 cc (M20/6-cylinder engine)
5-series, E28 body style (“old-shape”)
518 (1981 to 1985) and 518i (1985 to 1988) . . . . . . . . . . . . . . . . 1766 cc (M10/4-cylinder engine)
525i (1981 to 1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2494 cc (M30/6-cylinder engine)
528i (1981 to 1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2788 cc (M30/6-cylinder engine)
535i (1985 to 1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3430 cc (M30/6-cylinder engine)
M535i (1985 to 1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3430 cc (M30/6-cylinder engine)
5-series, E34 body style (“new-shape”)
518i (1990 to 1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1796 cc (M40/4-cylinder engine)
520i (1988 to 1991) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1990 cc (M20/6-cylinder engine)
525i (1988 to 1991) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2494 cc (M20/6-cylinder engine)
530i (1988 to 1991) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2986 cc (M30/6-cylinder engine)
535i (1988 to 1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3430 cc (M30/6-cylinder engine)
Firing order
Four-cylinder engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3-4-2
Six-cylinder engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5-3-6-2-4
Lubrication system
Oil pressure (all engines)
At idle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.5 to 2.0 bars
Running (for example, at 4000 rpm) . . . . . . . . . . . . . . . . . . . . . . . . . . 4 bars or above (typically)
Oil pump rotor clearance - M40 engine
(body-to-outer rotor/outer rotor-to-inner rotor) . . . . . . . . . . . . . . . . . . . 0.12 mm to 0.20 mm
Oil pump pressure relief valve spring length - M40 engine . . . . . . . . . . 84.1 mm
Chapter 2 Part A:
In-car engine repair procedures
Camshaft - removal, inspection and refitting . . . . . . See Chapter 2B
Compression check . . . . . . . . . . . . . . . . . . . . . . . . . See Chapter 2B
Crankshaft rear oil seal - renewal . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Cylinder head - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . 12
Cylinder head - dismantling and inspection . . . . . . . See Chapter 2B
Drivebelt check, adjustment and renewal . . . . . . . . See Chapter 1
Engine - removal and refitting . . . . . . . . . . . . . . . . . See Chapter 2B
Engine mountings - check and renewal . . . . . . . . . . . . . . . . . . . . . . 17
Engine oil and filter change . . . . . . . . . . . . . . . . . . . See Chapter 1
Engine overhaul - general information . . . . . . . . . . . See Chapter 2B
Exhaust manifold - removal and refitting . . . . . . . . . . . . . . . . . . . . . 6
Flywheel/driveplate - removal and refitting . . . . . . . . . . . . . . . . . . . 15
Front oil seals - renewal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
General information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Intake manifold - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . 5Oil pump - removal, inspection and refitting . . . . . . . . . . . . . . . . . . 14
Repair operations possible with the engine in the vehicle . . . . . . . . 2
Rocker arm and shaft assembly - dismantling, inspection
and reassembly . . . . . . . . . . . . . . . . . . . . . . . . . . . See Chapter 2B
Spark plug renewal . . . . . . . . . . . . . . . . . . . . . . . . . . See Chapter 1
Sump - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Timing belt and sprockets - removal, inspection and refitting . . . . . 10
Timing belt covers - removal and refitting . . . . . . . . . . . . . . . . . . . . . 9
Timing chain and sprockets - removal, inspection and refitting . . . . 8
Timing chain covers - removal and refitting . . . . . . . . . . . . . . . . . . . 7
Top Dead Centre (TDC) for No 1 piston - locating . . . . . . . . . . . . . . 3
Valve clearance check and adjustment . . . . . . . . . . . See Chapter 1
Valve cover - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Valves - servicing . . . . . . . . . . . . . . . . . . . . . . . . . . . See Chapter 2B
2A•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

2B
General
Cylinder compression pressure (all engines) . . . . . . . . . . . . . . . . . . . . . 10 to 11 bars
Oil pressure (all engines)
At idle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.5 to 2.0 bars
Running (for example, at 4000 rpm) . . . . . . . . . . . . . . . . . . . . . . . . . . 4 bars or above (typically)
Cylinder head warpage limit
Except M40 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.10 mm
M40 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.03 mm
Minimum cylinder head thickness (do not resurface the head to a thickness less than listed)
M10 and M30 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128.6 mm
M20 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124.7 mm
M40 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140.55 mm
Valves
Valve stem diameter (standard)
M10 and M30 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.0 mm
M20 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.0 mm
M40 engine
Intake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.975 mm
Exhaust . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.960 mm
Minimum valve margin width
Intake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.191 mm
Exhaust . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.98 mm
Valve stem maximum lateral movement (see text) . . . . . . . . . . . . . . . . . 0.787 mm
Valve face angle
Intake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45°
Exhaust . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45°
Chapter 2 Part B:
General engine overhaul procedures
Compression check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Crankshaft - inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Crankshaft - refitting and main bearing oil clearance check . . . . . . . 24
Crankshaft - removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Crankshaft rear oil seal - refitting . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Cylinder head and components - cleaning and inspection . . . . . . . 9
Cylinder head - dismantling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Cylinder head - reassembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Cylinder honing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Engine - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Engine block - cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Engine block - inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Engine overhaul - alternatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Engine overhaul - dismantling sequence . . . . . . . . . . . . . . . . . . . . . 7Engine overhaul - general information . . . . . . . . . . . . . . . . . . . . . . . 2
Engine overhaul - reassembly sequence . . . . . . . . . . . . . . . . . . . . . 21
Engine removal - methods and precautions . . . . . . . . . . . . . . . . . . . 4
General information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Initial start-up and break-in after overhaul . . . . . . . . . . . . . . . . . . . . 27
Intermediate shaft - refitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Intermediate shaft - removal and inspection . . . . . . . . . . . . . . . . . . . 14
Main and connecting big-end bearings - inspection . . . . . . . . . . . . 20
Piston rings - refitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Pistons/connecting rods - inspection . . . . . . . . . . . . . . . . . . . . . . . . 18
Pistons/connecting rods - refitting and big-end bearing oil
clearance check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Pistons/connecting rods - removal . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Valves - servicing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2B•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

Throttle positioner (2BE)
24Special tools are required to carry out a
comprehensive adjustment on the 2BE
carburettor. This work should therefore be left
to a BMW dealer.
13 Fuel injection -
general information
The fuel injection system is composed of
three basic sub-systems: fuel system, air
intake system and electronic control system.
Fuel system
An electric fuel pump, located inside the
fuel tank or beside the fuel tank, supplies fuel
under constant pressure to the fuel rail, which
distributes fuel evenly to all injectors. From
the fuel rail, fuel is injected into the intake
ports, just above the intake valves, by the fuel
injectors. The amount of fuel supplied by the
injectors is precisely controlled by an
Electronic Control Unit (ECU). An additional
injector, known as the cold start injector (L-
Jetronic and early Motronic systems only),
supplies extra fuel into the intake manifold for
starting. A pressure regulator controls system
pressure in relation to intake manifold
vacuum. A fuel filter between the fuel pump
and the fuel rail filters the fuel, to protect the
components of the system.
Air intake system
The air intake system consists of an air filter
housing, an airflow meter, a throttle body, the
intake manifold, and the associated ducting.
The airflow meter is an information-gathering
device for the ECU. These models are
equipped with the vane-type airflow meter. A
potentiometer measures intake airflow, and a
temperature sensor measures intake air
temperature. This information helps the ECU
determine the amount of fuel to be injected by
the injectors (injection duration). The throttle
plate inside the throttle body is controlled by
the driver. As the throttle plate opens, the
amount of air that can pass through the
system increases, so the potentiometer opens
further and the ECU signals the injectors to
increase the amount of fuel delivered to the
intake ports.
Electronic control system
The computer control system controls the
fuel system and other systems by means of
an Electronic Control Unit (ECU). The ECU
receives signals from a number of information
sensors which monitor such variables as
intake air volume, intake air temperature,
coolant temperature, engine rpm,
acceleration/deceleration, and exhaust
oxygen content. These signals help the ECU
determine the injection duration necessary for
the optimum air/fuel ratio. These sensors and
their corresponding ECU-controlled outputactuators are located throughout the engine
compartment. For further information
regarding the ECU and its relationship to the
engine electrical systems and ignition system,
refer to Chapters 5 and 6.
Either an L-Jetronic system or a Motronic
system is fitted. Later models have an
updated version of the original Motronic
system.
14 Fuel injection systems
L-Jetronic fuel injection system
The Bosch L-Jetronic fuel injection system
is used on most 3-Series models up to 1987,
and on most E28 (“old-shape”) 5-Series
models. It is an electronically-controlled fuel
injection system that utilises one solenoid-
operated fuel injector per cylinder. The system
is governed by an Electronic Control Unit
(ECU) which processes information sent by
various sensors, and in turn precisely
meters the fuel to the cylinders by
adjusting the amount of time that the injectors
are open.
An electric fuel pump delivers fuel under
high pressure to the injectors, through the fuel
feed line and an in-line filter. A pressure
regulator keeps fuel available at an optimum
pressure, allowing pressure to rise or fall
depending on engine speed and load. Any
excess fuel is returned to the fuel tank by a
separate line.
A sensor in the air intake duct constantly
measures the mass of the incoming air, and
the ECU adjusts the fuel mixture to provide an
optimum air/fuel ratio.
Other components incorporated in the
system are the throttle valve (which controls
airflow to the engine), the coolant temperature
sensor, the throttle position switch, idle
stabiliser valve (which bypasses air around
the throttle plate to control idle speed) and
associated relays and fuses.
Motronic fuel injection system
The Motronic system combines the fuel
control of the L-Jetronic fuel injection system
with the control of ignition timing, idle speed
and emissions into one control unit.
The fuel injection and idle speed control
functions are similar to those used on the L-
Jetronic system described above. For more
information on the Motronic system, see
Chapter 6.
An oxygen sensor is mounted in the
exhaust system on later models with a
catalytic converter. This sensor continually
reads the oxygen content of the exhaust gas.
The information is used by the ECU to adjust
the duration of injection, making it possible to
adjust the fuel mixture for optimum converter
efficiency and minimum emissions.
15 Fuel injection system-
check
2
Warning: Fuel is extremely
flammable, so take extra
precautions when you work on
any part of the fuel system. Don’t
smoke, or allow open flames or bare light
bulbs, near the work area. Don’t work in a
garage where a natural gas-type appliance
(such as a water heater or clothes dryer)
with a pilot light is present. If you spill any
fuel on your skin, rinse it off immediately
with soap and water. When you perform
any kind of work on the fuel system, wear
safety glasses, and have a fire
extinguisher on hand.
1Check the earth wire connections. Check
all wiring harness connectors that are related
to the system. Loose connectors and poor
earths can cause many problems that
resemble more serious malfunctions.
2Make sure the battery is fully charged, as
the control unit and sensors depend on an
accurate supply voltage in order to properly
meter the fuel.
3Check the air filter element - a dirty or
partially-blocked filter will severely impede
performance and economy (see Chapter 1).
4If a blown fuse is found, renew it and see if
it blows again. If it does, search for an earthed
wire in the harness related to the system.
5Check the air intake duct from the airflow
meter to the intake manifold for leaks. Intake
air leaks can cause a variety of problems. Also
check the condition of the vacuum hoses
connected to the intake manifold.
6Remove the air intake duct from the throttle
body, and check for dirt, carbon and other
residue build-up. If it’s dirty, clean it with
carburettor cleaner and a toothbrush.
7With the engine running, place a
screwdriver or a stethoscope against each
injector, one at a time, and listen for a clicking
sound, indicating operation (see illustration).
4•14 Fuel and exhaust systems
15.7 Use a stethoscope or screwdriver to
determine if the injectors are working
properly - they should make a steady
clicking sound that rises and falls with
engine speed changes

6If the voltage is correct, unplug the
electrical connector and, using an ohmmeter,
check for continuity between the terminals of
the thermotime switch (see illustration).
Continuity should exist.
7Reconnect the coil lead, start the engine
and warm it up above 41ºC. When the engine
is warm, there should be no continuity
between the terminals. If there is, the switch is
faulty and must be renewed. Note: On 5-
Series models, there are several types of
thermotime switch. Each one is stamped with
an opening temperature and maximum
duration.
Renewal
Cold start injector
8Depressurise the fuel system (see Sec-
tion 2).
9Disconnect the electrical connector from
the cold start injector.
10Where applicable, using a ring spanner or
deep socket, remove the fuel line fitting
connected to the cold start injector. On other
models, simply loosen the hose clamp and
detach the hose from the injector.
11Remove the cold start injector securing
bolts, and remove the injector.
12Refitting is the reverse of removal. Clean
the mating surfaces, and use a new gasket.
Thermotime switch
Warning: Wait until the engine is
completely cool before beginning
this procedure. Also, remove the
cap from the expansion tank or
radiator to relieve any residual pressure in
the cooling system.
13Prepare the new thermotime switch for
fitting by applying a light coat of thread
sealant to the threads.
14Disconnect the electrical connector from
the old thermotime switch.
15Using a deep socket, or a ring spanner,
unscrew the switch. Once the switch is
removed coolant will start to leak out, so
insert the new switch as quickly as possible.
Tighten the switch securely, and plug in the
electrical connector.
20 Fuel injectors-
check and renewal
2
Warning: Fuel is extremely
flammable, so take extra
precautions when you work on
any part of the fuel system. Don’t
smoke, or allow open flames or bare light
bulbs, near the work area. Don’t work in a
garage where a natural gas-type appliance
(such as a water heater or clothes dryer)
with a pilot light is present. If you spill any
fuel on your skin, rinse it off immediately
with soap and water. When you perform
any kind of work on the fuel system, wear
safety glasses, and have a fire
extinguisher on hand.
Check
In-vehicle check
1Using a mechanic’s stethoscope (available
at most car accessory shops), check for a
clicking sound at each of the injectors while
the engine is idling (see illustration 15.7).
2The injectors should make a steady clicking
sound if they are operating properly.
3Increase the engine speed above 3500 rpm.
The frequency of the clicking sound should
rise with engine speed.
4If an injector isn’t functioning (not clicking),
purchase a special injector test light (a car
accessory shop or fuel injection specialist
may be able to help) and connect it to the
injector electrical connector. Start the engine
and make sure the light flashes. If it does, the
injector is receiving the proper voltage, so the
injector itself must be faulty.
5Unplug each injector connector, and checkthe resistance of the injector (see
illustration). Check your readings with the
values listed in this Chapter’s Specifications.
Renew any that do not give the correct
resistance reading.
Volume test
6Because a special injection checker is
required to test injector volume, this
procedure is beyond the scope of the home
mechanic. Have the injector volume test
performed by a BMW dealer or other
specialist.
Renewal
7Unplug the main electrical connector for the
fuel injector wiring harness. Remove the
intake manifold (see Chapter 2A).
8Detach the fuel hoses from the fuel rail, and
remove the fuel rail mounting bolts (see
illustration).
9Lift the fuel rail/injector assembly from the
intake manifold.
10Unplug the electrical connectors from the
fuel injectors. Detach the injectors from the
fuel rail.
11Refitting is the reverse of removal. Be sure
to renew all O-rings. Coat the O-rings with a
light film of engine oil to prevent damage
during refitting. Pressurise the fuel system
(refit the fuel pump fuse and switch on the
ignition) and check for leaks before starting
the engine.
21 Idle air stabiliser valve-
check, adjustment and
renewal
4
1The idle air stabiliser system works to
maintain engine idle speed within a 200 rpm
range, regardless of varying engine loads at
idle. An electrically-operated valve allows a
small amount of air to bypass the throttle
plate, to raise the idle speed whenever the idle
speed drops below approximately 750 rpm. If
the idle speed rises above approximately
950 rpm, the idle air stabiliser valve closes
and stops extra air from bypassing the throttle
plate, reducing the idle speed.
4•18 Fuel and exhaust systems
20.8 Remove the bolts (arrowed) and
separate the fuel rail and injectors from
the intake manifold20.5 Check the resistance of each of the
fuel injectors19.6 Check the resistance of the
thermotime switch with the engine coolant
temperature below 30º C. There should be
continuity
If you don’t have a
mechanic’s stethoscope, a
screwdriver can be used to
check for a clicking sound at
the injectors. Place the tip of the
screwdriver against the injector, and
press your ear against the handle.

2L-Jetronic systems are equipped with a
separate idle speed control unit (computer)
located under the facia. The idle air stabiliser
valve has an adjusting screw. Early models
are equipped with plastic valves, but they still
can be adjusted by removing the hose and
inserting a very thin screwdriver inside.
3Early Motronic systems are also equipped
with a separate idle speed control unit
(computer) located under the facia. The idle
air stabiliser valve has an adjusting screw.
4On later Motronic systems, the idle air
stabiliser valve is ECU-controlled, and no
provision is made for adjustment.
Preliminary check
5Before performing any checks on the idle
air stabiliser valve, make sure these criteria
are met:
a) The engine must be at operating
temperature (60ºC)
b) Turn off all electrical accessories (air
conditioning, heater controls, headlights,
auxiliary cooling fan, etc)
c) The throttle position sensor must be
operating correctly (see Chapter 6)
d) There must not be any exhaust leaks
e) There must not be any vacuum leaks
f) Where fitted, the oxygen sensor must be
operating properly (see Chapter 6)
6Connect a tachometer in accordance with
the manufacturer’s instructions.
Caution: The ignition must be
switched off before making any
electrical connections.
7The idle air stabiliser valve operates
continuously when the ignition is on. Start the
engine and make sure the valve is vibrating
and humming slightly.
L-Jetronic system
Check
8With the engine running, disconnect the
electrical connector from the valve. The idle
speed should increase to about 2,000 rpm.
9If the idle speed does not increase, turn the
engine off. Using an ohmmeter, check the
resistance across the terminals of the valve(see illustration). It should be 9 to 10 ohms
with the ambient air temperature at about
20º C.
10Using a pair of jumper wires, apply battery
voltage to the valve, and confirm that the
valve closes tightly. When the voltage is
removed, the valve should re-open.
11If the idle air stabiliser valve fails any of
the tests, renew it.
12If the idle air stabiliser valve passes the
tests, check the control current.
13Unplug the electrical connector from the
valve. Using a jumper wire, connect one
terminal of the electrical connector to one of
the terminals on the valve, Connect an
ammeter (0 to 1000 mA range) between the
other terminal on the electrical connector and
the remaining terminal on the valve. Start the
engine and allow it to idle. With the engine
running, the current reading should be
between 400 and 500 mA. Adjust the valve if
the current reading is not as specified (see
paragraph 15). Note: The idle air stabiliser
current will fluctuate between 400 and
1100 mA if the engine is too cold, if the
coolant temperature sensor is faulty, if the idle
speed needs to be adjusted, if there is an
engine vacuum leak or if electrical accessories
are on.
14If there is no current reading, have the idle
speed control unit diagnosed by a BMW
dealer or other specialist. Note: The idle air
stabiliser control unit (located under the facia)
can develop an electrical connector problem
that intermittently turns the valve on and off.
Check the connector very carefully before
fitting any new parts. Sometimes, a new
control unit will only fix the problem
temporarily.
Adjustment
15With the ignition switched off, connect a
tachometer in accordance with the equipment
manufacturer’s instructions.
16Make sure the ignition timing is correct
(see Chapter 5).
17Connect an ammeter to the valve (see
paragraph 13).
18With the engine running, the current
reading should be 450 to 470 mA at 850 to900 rpm (manual transmission), or 460 to
480 mA at 850 to 900 rpm (automatic
transmission).
19If the control current is not correct, turn
the adjusting screw until it is within the correct
range (see illustration). Note: On metal-type
valves, the adjusting screw is mounted
externally. On plastic-type valves, the
adjustment screw is inside, and can be
reached by removing the hose at the end of
the valve.
Motronic systems
Check
Note:There are two types of idle air stabiliser
valve on these systems; early models usually
have a two-wire valve, while later models are
equipped with a three-wire valve.
20With the engine running, disconnect the
electrical connector from the valve. The idle
speed should increase to about 2000 rpm.
21If the idle speed does not increase:
a) Two-wire valve - Using a pair of jumper
wires, apply battery voltage to the valve,
and confirm that the valve closes tightly.
When the voltage is removed, the valve
should re-open. Also, check the
resistance of the valve (see illus-
tration 21.9). The resistance should be
about 9 or 10 ohms.
b) Three-wire valve - Turn the engine off and
unplug the electrical connector from the
valve. Using an ohmmeter, check the
resistance on the two outer terminals of
the valve. (see illustration). It should be
about 40 ohms. Check the resistance on
the centre and outside terminals of the
valve. They should both be about
20 ohms.
22If the idle air stabiliser valve fails any of
the tests, renew it.
23If the idle air stabiliser valve tests are all
correct, check the control current (two-wire
valve) or the voltage (three-wire valve) as
follows.
24On two-wire valves, connect an ammeter
(0 to 1000 mA range) as described in
paragraph 13. Start the engine, and allow it to
idle. With the engine running, the current
Fuel and exhaust systems 4•19
21.21 Check the idle air stabiliser valve
resistance on the two outer terminals on
later Motronic systems - it should be about
40 ohms21.19 Location of the adjustment screw on
the metal-type idle air stabiliser valve
(L-Jetronic system)21.9 Check the resistance of the idle air
stabiliser valve - it should typically be 9 to
10 ohms (L-Jetronic system)
4

reading should be between 400 and 500 mA.
Adjust the valve if the current reading is not as
specified. Note: The idle air stabiliser current
will fluctuate between 400 and 1100 mA if the
engine is too cold, if the coolant temperature
sensor is faulty, if there is an engine vacuum
leak, or if electrical accessories are on.
25If there is no current reading, have the idle
speed control unit (under the facia) checked
by a BMW dealer or other specialist.
26On three-wire valves, check for voltage at
the electrical connector. With the ignition on,
there should be battery voltage present at the
centre terminal (see illustration). There
should be about 10 volts between the centre
terminal and each of the outer terminals.
27If there is no voltage reading, have the idle
speed control unit (early models) or the ECU
(later models) checked by a dealer service
department or other specialist.
Adjustment (early models only)
28With the ignition switched off, connect a
tachometer in accordance with the equipment
manufacturer’s instructions.
29Make sure the ignition timing is correct
(see Chapter 5).
30Connect an ammeter to the valve as
described in paragraph 13.
31With the engine running, the current draw
should be 450 to 470 mA at 700 to 750 rpm.
32If the control current is not correct, turn
the adjusting screw until it is within the
specified range. Note: Turn the idle air bypass
screw clockwise to increase the current, or
anti-clockwise to decrease the current.
Renewal
33Remove the electrical connector and the
bracket from the idle air stabiliser valve.
Remove the valve, disconnecting the hoses.
34Refitting is the reverse of removal.
22 Exhaust system servicing-
general information
Warning: Inspect or repair
exhaust system components only
when the system is completely
cool. When working under the
vehicle, make sure it is securely
supported.
Silencer and pipes
1The exhaust system consists of the exhaust
manifold, catalytic converter, silencers, and all
connecting pipes, brackets, mountings (see
illustration)and clamps. The exhaust system
is attached to the body with brackets and
rubber mountings. If any of the parts are
improperly fitted, excessive noise and
vibration may be transmitted to the body.
2Inspect the exhaust system regularly. Look
for any damaged or bent parts, open seams,
holes, loose connections, excessive
corrosion, or other defects which could allow
exhaust fumes to enter the vehicle. Generally,
deteriorated exhaust system components
cannot be satisfactorily repaired; they should
be renewed.3If the exhaust system components are
extremely corroded or rusted together, it may
be necessary to cut off the old components
with a hacksaw. Be sure to wear safety
goggles to protect your eyes from metal
chips, and wear work gloves to protect your
hands.
4Here are some simple guidelines to follow
when repairing the exhaust system:
a) Work from the back to the front of the
vehicle when removing exhaust system
components.
b) Apply penetrating oil to the exhaust
system nuts and bolts to make them
easier to remove.
c) Use new gaskets, mountings and clamps
when fitting exhaust system components.
d) Apply anti-seize compound to the threads
of all exhaust system nuts and bolts
during reassembly.
e) Be sure to allow sufficient clearance
between newly-fitted parts and all points
on the underbody, to avoid overheating
the floorpan, and possibly damaging the
interior carpet and insulation. Pay
particularly close attention to the catalytic
converters and heat shields. Also, make
sure that the exhaust will not come into
contact with suspension parts, etc.
Catalytic converter
5Although the catalytic converter is an
emissions-related component, it is discussed
here because, physically, it’s an integral part
of the exhaust system. Always check the
converter whenever you raise the vehicle to
inspect or service the exhaust system.
6Raise and support the vehicle.
7Inspect the catalytic converter for cracks or
damage.
8Check the converter connections for
tightness.
9Check the insulation covers welded onto the
catalytic converter for damage or a loose fit.
Caution: If an insulation cover is
dented so that it touches the
converter housing inside,
excessive heat may be
transferred to the floor.
10Start the engine and run it at idle speed.
Check all converter connections for exhaust
gas leakage.
4•20 Fuel and exhaust systems
22.1 A typical exhaust system rubber
mounting21.26 Check for battery voltage on the
centre terminal

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