Porsche 928 Workshop Manual page 559

28
Ignition System
928
1. Adjust secondary display on ignition
oscilloscope.
Connect terminals 1 and 15 on left or right
ignition coil, inductive clip on left or right
ignition coil terminal 4 and trigger clip
on cylinder 1 for left ignition circuit and
cylinder 2 for right ignition circuit.
3-k ~Lr!-l,i
Note:
If an error is displayed for all cylinders,
it will be in the primary or secondary
circuit between the ignition coil and
distributor rotor.
If the error is on only one cylinder, it will
be after the distributor rotor.
2. Check distributor caps for damage, dirt
and traces of burning.
Resistance value: 1 k-ohm.
Holding hooks must engage firmly when
installing.
3. Check distributor rotor.
Shielded resistance: 1 k-ohm.
Check visually for damage and tight fit.
4. Check spark plug connectors and lines for
damage and traces of burning.
Shielded resistance: 3 k-ohms.
5. Check ignition coils.
Primary resistance of term. 1 versus
term.
15: 0.4 to 0.7 ohm.
Secondary resistance of term. 1 versus
term. 4: 5 to 8.7 k-ohms.
Check that plugs are not missing.
If plugs are missing or casting compound
has run out, replace ignition coil and
ignition control unit.
Note:
Avoid an ignition test via the spark gap by
pulling off the spark plug connectors.
There would be danger of destroying the
ignition coil and control unit.
28-62
Troubleshooting Electronic Ignition System
Printed
in Germany