BMW 1989-1995 525i Service Manual page 158

120-6
IGNITION SYSTEM-DME
6502.lGN 5·6
Fig . 8. Crankshaft position/rpm sensor connector (arro w).
Crankshaft positionlrpm sensor specifications
• Coil resistance (approx.) terminals 1 and 2
M20/M30 engines 540
±
10% ohms
M50/M60 engines . . . . . . . . . . . . . 1280
±
10% ohms
• Air gap (sensor distance from
toothed wheel ) 1.0
±
0.3 mm (0.04
:l:
0.01 in.)
3. If the resistance is not correct. the sensor is faulty and
should be replaced.
NO TE -
To rep /ace a faulty sensor. remove tti e sensor mount-
ing boll us ing a
5
mm hex wrench. Cu r wire ties as nee-
essary
to tne
rem ove wiring . When msralling
tne
ne w
sensor. be sure rhe wiring is rerou ted in tne same ori-
entstion . Secure rhe sensor us ing new wire ties.
Tighten ing Torque
• Crankshaft position/rpm sensor to
mounting bracket 7 ± 1 Nm (62
±
9 in-lb)
Ignition Firing Order
On M20 and M30 engines. spark plug wires must be in-
stalled so that the spark plugs fire in a specified order . The ro-
tor turns in a clockwise direct ion when viewed from the front
with the cap removed . Fig. 9 shows the correct routing of the
spark plugs wires in the distributor cap.
NOTE -
• On
e-cyunaer
engines. cyfinde r no. 1 is
ar
the fronr of
tne
engme.
• On 8·cylin der engines. cylinder no.
1
is
ar
the
trent
of
the engine on tne righ r-han d cytmder head.
fGNlTlO N
SYSTEM SERVICE
Ignition
coil wire
Fig. 9. Spark plugs wires correctly Installed in cistnbutor cap
(M201M30 engines).
Ig ni ti on Firing Order
• M20. M30. M50 engines 1-5-3-6-2-4
• M60 engines . . . . . . . . . . . . . . . . . . . . 1·5 ·4·8·6 -3·7·2
Knock Sensors
Knock sensors are used on DME 3.3 and later engine man-
agemen t systems. M50 engines use two knock sensors and
the M60 engines use four sensors. The knock sensors are
bolted to the cylinder block and monitor the com bustion cham-
ber for engine·damaging knock. If knock is detected, the igni-
tion point is retarded accordingly via the DME contro l module.
On M50 engines , the knock sensors are acce ssible after re-
moving the top engine covers . On M60 engines. access to the
knock sensor requires remova l of the intake manifold.
CAUT/ON -
On OME
3.3
and
3.3. 1
eng ines. do nor inter-
c/la ng e rile kn ock se nsor harness
connectors.
Serious engine da mag e may
resun
if
tne
sensors
are
monitorinq
rile wro ng cylinders. If rile
connec-
rors need
ro
be remove d. be sure
ro
fabef them be -
fore disco nnecting .
NOTE -
• Knock sensor
tunction
is monitored by tile On -board
d iag nostic system. If
a
knock sensor is detected to be
faulty. an appropriate diagnostic troubfe code (OTC)
may be stored tn memory. See
100
Eng ine-General
for informa tion on re trieving OTCs.
• On M60 engmes. inrake man ifold rem ova l procedures
are
oescrioea
as
parr of cylinder
neeo removet
in 113
Cylinder Head Removal and Installation.