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

6 INSTALLATION INSTRUCTIONS
M S D
• 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
2-Step Limit: This rpm limit is activated
when 12 volts are applied to the Blue
wire. When activated, this limit overrides
the Max Limit. This limit is adjustable
from 1,000 to 9,900 and will default to
1,000 rpm if the dials are set to an rpm
below this range. An example of wiring
the 2-Step Limit so it is activated with the
line-lock is shown in Figure 3.
TO TRANS-BRAKE
OR LINE-LOCK SOLENOID
BLUE
TO 12V
Figure 3 Wiring the 2-Step Rev Limit.
PRESTART CHECK LIST
• The only wires connected to the coil terminals are the MSD Orange to coil positive and Black to coil negative.
• The small Red wire of the MSD is connected to a switched 12 volt source.
• Confirm the cylinder select is in the proper position for your application.
• The MSD power leads are connected directly to the battery positive and negative terminals.
• The battery is connected and fully charged if not using an alternator.
• The engine is equipped with at least one ground strap to the chassis.
TROUBLESHOOTING
LED
The LED on the side of the MSD monitors several operating conditions of the MSD. If the LED indicates
that there is a problem with the ignition system, follow the steps through the Troubleshooting section.
The LED will appear to be on steady above idle speeds when everything is functioning properly.
• Flashes once per second if the battery supply voltage is low when under 3,000 rpm (while
multiple sparking). This indicates a charging problem or poor connection.
• It will flash approximately once per second if the battery input voltage is above 28 volts for
a sustained amount of time.
• The LED will flash for every trigger signal from the distributor or crank trigger. You can take
advantage of this when statically setting the timing when using the White or White/Blue wire to trigger.
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 in Figure 4 lists common tachometers
and if an Adapter is necessary.