MSD 7805 8-Plus Ignition Control Installation - Manual (Page 4)

4 INSTALLATION INSTRUCTIONS
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ROUTING WIRES
The MSD wires should be routed away from direct heat sources such as exhaust manifolds and
headers and any sharp edges. The trigger wires should be routed separate from the other wires
and spark plug wires. It is best if they are routed along a ground plane such as the block or firewall
which creates an electrical shield. The magnetic pickup wires should always be routed separately
and should be twisted together to help reduce extraneous interference (the harness supplied is
already twisted).
The chart shows the polarity of other common magnetic pickups. If using a different magnetic pickup,
use the MSD 2-Pin connector, available as PN 8824, for a direct plug-in installation.
WARNING: The MSD-8-Series Ignitions are capacitive
discharge ignitions. High voltage is present
at the coil primary terminals. Do not touch
the coil or connect test equipment to the
terminals.
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.
• 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
Every MSD Ignition undergoes numerous quality control checks including a four hour burn-in test.
If you experience a problem with your MSD, our research has shown that the majority of problems
are due to improper installation or poor connections.
The Troubleshooting section has several checks and tests you can perform to ensure proper
installation and operation of the MSD. If you have any questions concerning your MSD, call our
Customer Support Department at (915) 855-7123, 7 - 6 mountain time.
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.
Common Mag Pickup Wires
Distributor Colors
Mag+ Mag-
MSD Org/Blk Vio/Blk
MSD Crank Trigger Org/Blk Vio/Blk
Ford Orange Purple
Accel 46/48000 Series Org/Blk Vio/Blk
Accel 51/61000 Series Red Black
Chrysler Org/Wht Black
Mallory Org/Blk Vio/Blk
Figure 4 Common Mag Pickup Wires.