Porsche 928 Workshop Manual page 555

28
Ignition System
928
a
2. Detach vacuum connection on intake
distributor.
This should reduce ignition timing to
20 2 3".
3. If 40 C 3' ignition timing angle is not
reached, supply approx. 500 mbar vacuum
direct on control unit with help of a manual
pump.
If specified ignition timing is still not
reached, replace electronic ignition control
unit.
If ignition timing is correct after supplying
vacuum to the control unit, check
vacuum hose between electronic ignition
control unit and intake air distributor for
leaks.
TEST POINT 5
Temperature Sensor I
(Intake Air Temperature)
1. Check plug connection on temperature
sensor I underneath the air cleaner housing
for tight fit and clean contacts.
2. Connect ohmmeter between terminals 10
and 22 on disconnected plug of electronic
ignition control unit.
Specifications:
0 "Cl 32"F=4.4to6.8kS2
15 to 30 "C/59 to 86 OF = 1.4 to 3.6 kQ
40 "Cl 104 "F = 0.9 to 1.3 kn
28 58
Troubleshooting Electronic Ignition System
Printed in Germany
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a