INSTALLATION INSTRUCTIONS 7
MSD • WWW.MSDPERFORMANCE.COM • (915) 857-5200 • FAX (915) 857-3344
GM: Install the Diode in-line to the wire going
to terminal “4”.
GM 1973 - 1983 with Delcotron Alternators
GM Delcotron Alternators use an internal
voltage regulator. Install the Diode in-line
on the smallest wire exiting the alternator
(Figure 6). It is usually a Brown wire.
MISSES AND INTERMITTENT PROBLEMS
Experience at the races has shown that if your engine is experiencing a miss or hesitation at higher
rpm, it is usually not directly ignition related. Most probable causes include a coil or plug wire failure,
arcing from the cap or boot plug to ground or spark ionization inside the cap. Several items to
inspect are:
• Always inspect the plug wires at the cap and at the plug for a tight connection and visually
inspect for cuts, abrasions or burns.
• Inspect the Primary Coil Wire connections. Because the MSD is a Capacitive Discharge
ignition and it receives a direct 12 volt source from the battery, there will not be any
voltage at the Coil Positive (+) terminal even with the key turned On. During cranking or
while the engine is running, very high voltage will be present and no test equipment should
be connected.
• Make sure that the battery is fully charged and the connections are clean and tight. If you
are not running an alternator this is an imperative check. If the battery voltage falls below
10 volts during a race, the MSD output voltage will drop.
WARNING: Do not touch the coil terminals during cranking or while the engine is running.
• Is the engine running lean or excessively rich? Inspect the spark plugs and fuel system.
• Inspect all wiring connections for corrosion or damage. Remember to always use proper
connections followed by soldering and seal the connections completely.
LED: The LED on the ignition will assist in troubleshooting. If the LED does not ash, there is no
current through the primary coil wires. This could be due to poor connections at the coil, the
coil itself or the ignition. Once you conrm that the trigger signal is working, try a different
coil. See page 8 to test for spark.
If everything checks positive, use the following procedure to test for spark. MSD also offers an
Ignition Tester, PN 8998. This tool allows you to check your complete ignition system while it is in the
car as well as the operation of rpm limits, activated switches and shift lights.
Figure 5 Installing the Diode to a GM or Ford Vehicle.
Figure 6 Installing the Diode to a 1973-1983 GM Vehicle.
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