Porsche 1989 944 S2, Workshop Manual

Page: 159 / 167

944 S/944 S2 Fuel System - Electronic Control
24/28
No display:
Disconnect plug of speed sender on plug
plate in the engine compartment. Connect
tester leads on middle and outside pins of
the plug on the sender end of the plug with
help of test leads (terminals 1 and 2, pin
end). Start the engine. Sinusoidal oscillation
must be displayed on the screen.
Speed sender plug
Remarks:
The display must remain unchanged after
supplying ground to connection 3.
If not, check power flow, spacing and
condition of the sender.
Test Point 22: Ignition
a) Secondary ignition display
Adjust secondary ignition display an the
oscilloscope. Connect tester leads according
to the supplied operating instructions.
Note:
If a fault is displayed for all cylinders, it is in
the primary or secondary circuit from the
ignition coil to the distributor rotor. If a fault is
displayed for one cylinder, this fault is
located after the distributor rotor.
Primary resistor:
Secondary
resistor:
Term.1 + 15 = 0.4-0.6
Term.1 + 4 = 5-7.2 k
b) Spark plug connectors ( )
Suppression resistor: 3 k
Visual inspection for damage or traces of
burning.
c) Distributor
Distributor rotor, distributor cap: suppression
resistor = each 1 k .
Visual inspection for damage, dirt or wrong
location.
DME - Diagnosing/Troubleshooting
Printed In Germany - XXI, 1989
D 24/28 - 25