Porsche 944 - Manual (Page 162)

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Fuel System - Electronic Control 944 S/944 S2
Test Point 23: Fuel Injectors -
Injection Timing (V/ )
Element activation menu:
If a pulse is not heard, check:
a) Power supply
Pull off injector plug. Connect voltmeter on
injector plug terminal 2 and ground with help
of test leads. Turn on ignition.
Display: battery voltage
If there is no dispiay:
Disconnect 5-pin plug of fuel injector ballast
resistors. Connect voltmeter between
terminal 3 (terminal sleeve end) and ground.
Turn on ignition.
If battery voltage is displayed, Turn off
ignition and pull off all plugs on fuel injectors.
Check power flow and resistance between
the S-pin plug of ballast resistors and
terminal 2 of each fuel injector plug with an
ohmmeter.
Resistance of each ballast resistor = 6
Check current path according to the wiring
diagram if battery voltage is not displayed.
b) Coil resistanee test of fuel injectors
Pull off injector plugs. Check coil resistance
on the contacts of the fuel injectors with an
ohmmeter.
Test value: 2 - 3
c) Injection final stage
Adjust oscilloscope according to the
supplied operating instructions. Connect
Bosch test lead (1 684 463 093) between
fuel injector and plug. Connect tester leads
on Bosch lead according to the supplied
operating instructions.
Caution:
Tester leads must not have any contact
with ground.
Start the engine. These displays must
appear in the oscilloscope if the injection
final stage is working perfectly and test
connections are correct.
Starter speed
Remarks:
If the engine cannot be started or the idle
speed drops, change tester connections on
the Bosch lead and check tester
adjustment.
D 24/28 - 28 DME - Diagnosing/Troubleshooting
Printed In Germany - XXI, 1989