Porsche 928 Workshop Manual page 554

928
Ignition System
28
Sine oscillations of at least 2.5 V (speed
signal) and oscillation with definitely higher
amplitude (reference mark signal) must be
displayed on the screen.
If the amplitude of the speed signal is less
than 2.5 V or no signal is displayed, check
connections and test the sensor.
Measure internal resistance of terminal 7
against terminal 19 on the electronic
ignition plug or on the speed/reference mark
sensor plug connection.
TEST POINT 4
Pressure Sensor
(Integrated in Electronic
Ignition Control Unit)
Connect adjustable ignition timing light or
engine tester with TDC sensor system on
engine.
7 19 26
Note:
Tester must be set to "4 cylinders".
Specification: 0.6 to 1.6 k-ohms.
If necessary,
replace speed/reference mark sensor.
1. Accelerate engine in stopped car to
4,000 rpm.
Ignition timing angle should be
40 f 3".
Printed inGermany - VIII, 1984
Troubleshooting Electronic Ignition System 28 - 57