MSD 7222 7AL-2 Ignition Control Installation - Manual (Page 6)

6 INSTALLATION INSTRUCTIONS
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TACH/FUEL ADAPTERS
If your tachometer does not operate correctly or if you experience a no-run situation with your foreign
vehicle you probably need an MSD Tach Adapter. The chart below lists common tachometers and if
an Adapter is necessary.
INOPERATIVE TACHOMETERS
If your tachometer fails to operate with the MSD installed you may need an MSD Tach Adapter. Before
getting an Adapter, try connecting your tachometer trigger wire to the tach output terminal on the
side of the MSD. This output produces a 12 volt, square wave (see page 2). If the tach still does not
operate, you will need a Tach Adapter. There are two Tach Adapters:
PN 8920: If you are using the Magnetic Pickup connector (Green and Violet wires) to trigger the
MSD, you will need the PN 8920.
PN 8910: If your tachometer was triggered from the coil negative terminal (voltage trigger) and you
are using the White wire to trigger the MSD you will need the PN 8910.
ENGINE RUN-ON
If your engine continues to run even when the ignition is turned Off you are experiencing engine Run-
On. This usually only occurs on older vehicles with an external voltage regulator. Because the MSD
receives power directly from the battery, it does not require much current to keep the unit energized.
If you are experiencing run-on, it is due to a small amount of voltage going through the charging
lamp indicator and feeding the small Red wire even if the key is turned off.
Early Ford and GM: To solve the Run-On problem, a Diode is supplied with the MSD in the parts
bag. By installing this Diode in-line of the wire that goes to the Charging indicator, the voltage is kept
from entering the MSD. Figure 5 shows the proper installation for early Ford and GM vehicles.
Note: Diodes are used to allow voltage to flow only one way. Make sure the Diode is installed
facing the proper direction (as shown in Figure 5).
Ford: Install the Diode inline to the wire going to the “1” terminal.
Tachometer Compatibility List
AFTERMARKET TACHOMETER WHITE WIRE TRIGGER MAGNETIC TRIGGER CONNECTOR
AUTOGAGE 8910 8920
AUTOMETER NONE NONE
FORD MOTORSPORTS NONE NONE
MALLORY NONE NONE
MOROSO NONE NONE
STEWART 8910 8920
S.W. & BI TORX NONE NONE
SUN 8910 8920
VDO 8910 8920
AMC (JEEP) 8910 8920
CHRYSLER 8910 8920
FORD (Before 1976) 8910 8920
FORD (After 1976) 8910 8920
GENERAL MOTORS Bypass In-Line Filter Bypass In-line filter
IMPORTS 8910 8920
Note: On the list above, the trigger wire on tachometers that are marked NONE may be connected to the
Tach Output Terminal on the MSD 7 Series Ignition Unit using the supplied Female Faston Receptacle.