8

INSTALLATION INSTRUCTIONS

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 6 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 6).

Ford: Install the Diode in-line to the wire going to the “1” terminal.

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

7). It is usually a Brown wire.

SMALLER OF THE 2-WIRES

DIODE

WIRE LOOM

GM 2-WIRE ALTERNATORS

Figure 7 Installing the Diode to a

1973-1983 GM Vehicle.

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. Most probable causes include faulty wiring, 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.

WARNING: Do not touch the coil terminals during cranking or while the engine is running.

• 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 9 volts during a

race, the MSD output voltage will drop and the current draw will increase.

• Is the engine running lean? Inspect the spark plugs and complete fuel system.

• Inspect all wiring connections for corrosion or damage. Remember to always use proper connections

followed by soldering and seal the connections completely.

Most other applications: On

other applications where engine

Run-On is experienced, a

Resistor can be put in-line

to the MSD's small Red wire

(Figure 8). This resistor will keep

voltage from leaking through to

the MSD unit.

Figure 8 Wiring the Dual Ballast Resistor for Run-On.

MSD