MSD 6421 6AL-2 Ignition Control Installation - Manual (Page 7)

INSTALLATION INSTRUCTIONS 7
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• W W W . M S D P E R F O R M A N C E . C O M • ( 9 1 5 ) 8 5 5 - 7 1 2 3 • F A X ( 9 1 5 ) 8 5 7 - 3 3 4 4
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 (voltage triggered) 8910 8920
S.W. & BI TORX NONE NONE
SUN 8910 8920
VDO NONE NONE
AMC (JEEP) 8910 8920
CHRYSLER 8910 8920
FORD (voltage triggered) 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 Gray
Tach Output Wire on the MSD 6AL-2 Ignition.
Figure 4 Common Tachometers and Adapters.
NO-RUN ON FOREIGN VEHICLES
Some foreign vehicles with fuel injection systems may require an MSD Tach/Fuel Injection Adapter
to run with an MSD 6 Series Ignition. This is because many of these systems use the same trigger
source to operate the MSD, the tachometer and the fuel injection. This results in a voltage signal
that is too low to accurately trigger the fuel injection. To fix this, an MSD Tach Adapter, PN 8910, will
remedy the problem on the majority of vehicles. If the PN 8910 does not fix the problem, the PN
8910-EIS will be required.
Note: Toyotas and Ford Probes will require the PN 8910-EIS Adapter.
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 Gray tach wire 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.
BALLAST RESISTOR
If you have a current trigger tach (originally coil positive)
and use the White wire of the MSD, you can purchase a
Chrysler Dual Ballast Resistor (used from 1973 - 1976)
and wire it as shown in Figure 5.
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
1A-100V DIODE
FORD VEHICLES
ATTACH DIODE TO TERMINAL "1"
EARLY GM VEHICLES
ATTACH DIODE TO TERMINAL "4"
TO
CHARGING
LIGHT
SPLICE HERE
1
2
3
4
Figure 5 Wiring the Dual Ballast Resistor.
Figure 6 Installing the diode to a GM or Ford Vehicle.