BMW 1989-1995 525i Service Manual page 157

To remove the rotor mounting screws use a 3mm allen
wrench.
On M20 engines, remove the dust shield and inspect the
large O-ring on the rear of the shield. See Fig. 6. If the O-ring
is crushed or damaged, it should be replaced . Installation of
the rotor and cap is the reverse of removal. Do not over tighten
the rotor mounting screws.
IGNITION SYSTEM-DME
n
I
Cm ~ ITIDJ
120-5
Rotor
Dust
shield
O-ring
65 10.1 GN4-1
6510
Fig . 6. Ignition rotor, distributor cap dust shield and O-ring on M20
engine.
Tightening Torque
• Ignition rotor to
rotor adaptor 2.8±O.2 Nm (25±1.8 in-Ib)
NOTE-
The inductive pickup (cylinder identification sensor) on
the spark plug wire is used to sequence the fuel injec-
tors. See 130
FuellnJectlon-DME.
To test ignition coil (M50/M60 engines)
1. Remove the plastic engine cover(s) from the top of the
engine by prying off the nut covers and removing the
cover mounting nuts.
2. Disconnect the harness connector from the coil. Con-
nect a voltmeter between terminal 15 (+) in the harness
connector and ground. See Fig. 7. Turn the ignition on
and check for battery voltage.
• If battery
voltage is not present, check the wire be-
tween terminal 15 and the ignition switch. See Elec-
trical Wiring Diagrams.
3. Turn the ignition off.
11502
Fig. 7. Ignition coil harness connector terminal identification for M50
and MOO engines.
CAUTION-
The wiring to terminal 15 of the coil (via the igni-
tion switch) is not fuse protected. Use care when
testing this circuit.
4. Use an ohmmeter to test the coil primary. Resistance
values are listed in Table
b.
Table b. Ign ition Coil Resistance
(M50/M60 engines)
I
Terminals Resistance
Coil primary 1 (-) and t5 (+l 0.4·0 .8
n
Coil secondary
N.A. N.A.
5. Remove the coil and inspect the coil housing for hair-
line cracks or leaking casting material. If any faults are
found, the coil should be replaced.
NOTE-
On "May and Cntiste" manufactured coils. check care-
fully for thermal stress cracks or signs 01leaking cast -
ing material. If any of these faults are found, the coil
should be replaced before it causes damage to the
DMEECM.
Testing crankshaft position/rpm sensor
The crankshaft position/rpm sensor is mounted to the front
of the engine and reads a toothed wheel on the front of the
crankshaft . Engine speed is determined by the rate at which
the wheel's teeth pass the sensor. Crankshaft position is de-
termined by the missing-teeth gap on the
pulse wheel. If the
DME control module does not receive a crankshaft position
signal during cranking the engine will not start.
1. Disconnect the sensor harness connector.
2. Using an ohmmeter, check the resistance between the
terminals 1 and 2 in the sensor end of the connec tor.
See Fig. 8.
IGNITION SYSTEM SERVICE