Porsche 928 Workshop Manual page 578

928 s4
928 GT Fuel System - Electronic Control
24128
Important vehicle information
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Always turn off the ignition or disconnect the battery for resistance tests (if this is not done, the
measuring instrument may be damaged beyond repair).
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Always disconnect both speed sensor plugs for compression tests. (If this is not done,danger-
ously high voltages and insulation damage at the coil, high-tension distributor and Ignition leads
could result.)
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The specified coil (refer to order number) must not be replaced by a different coil.
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Never connect an interference suppression capacitor to coil terminals 1 and 15,
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Never connect coil terminal 1 to ground for the burglar alarm. This could damage the coil and the
control unit beyond repair.
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Never connect battery + or a test lamp to coil terminal 1, or the control unit will be damaged bey-
ond repair.
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Never disconnect the ignition lead from coil terminal 4 to high-tension distributor terminal 4 while
the engine is running.
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There must be no electrical flashover from coil terminal 4 to coil terminals 1 and 15, or the control
unit could be damaged beyond repair.
. To avoid destruction of the control unit, the secondary circuit of the ignition system must be
suppressed with at least 4 kQ; the original distributor rotor with 1 kS2 suppressor resistor must be
installed (do not use a 5 KQ -distributor rotor even if radio and telephone interference suppres-
sion are necessary).
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Disconnect EZWLH control units and ignition output stage plugs only after turning off the ignition.
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Flashovers or insulation breakdowns in the high-tension distributor cap area (poor isulation) could
destroy the control unit.
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Never disconnect the battery when the engine is running.
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Incorrect battery polarity could damage the ignition output stage, coil and LH-EZK control unit
beyond repair.
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External engine starting at more than 16 V or with a rapid battery charger is forbidden.
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Always comply with accident prevention regulations when working on the fuel system.
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DME Dlagnosingnroubleshooting
PrInted In Germany - Xxv, 1990
D 24120 - 3