8

INSTALLATION INSTRUCTIONS

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

is6turned 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.

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 6 Installing the diode to a GM or Ford Vehicle.

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.

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.