Checking The MSD Ignition For Spark
The following test will determine if your MSD is producing a spark.

White Wire Trigger:
If you are using the White wire (points or electronic amplifier) of the MSD to trigger the ignition, follow these steps.

1. Make sure the ignition switch is in the Off position.

 

2. Remove the coil wire from the distributor cap and position the terminal so it is approximately 1/2" from a good ground.

 

3. Disconnect the MSD White wire from the distributor points or the ignition amplifier.

 

4. Turn the ignition to the On position. DO NOT CRANK THE ENGINE.

 

5. Tap the White wire to ground several times. Each time the wire is pulled away from ground a spark should jump from the coil wire to ground. If spark is present, the ignition is working properly.

If there is no spark:

A. Inspect all of the wiring.

 

B. Substitute another coil and test again. If there is now spark, the coil is at fault.

 

C. If there is still no spark, check to make sure there is 12 volts on the small Red wire from the MSD when the key is in the On position. If 12 volts are not present, find another 12 volt source and repeat the test.

 

D. After inspecting the test procedures and inspecting all of the wiring, there is still no spark, the Ignition is at fault. See the Warranty and Service Page for Information.

Magnetic Pickup Trigger:
If you are using the 2-Pin Magnetic Pickup of the MSD to trigger the ignition, follow these steps.

1. Make sure the ignition switch is in the Off position.

 

2. Remove the coil wire from the distributor cap and position the terminal so it is approximately 1/2" from a good ground.

 

3. Disconnect the MSD Magnetic Pickup connector from the distributor.

 

4. Turn the ignition to the On position. DO NOT CRANK THE ENGINE.

 

5. With a small jumper wire, short the Green and Violet magnetic pickup wires together then pull the jumper off. Each time the short is removed a spark should jump If spark is present, the ignition is working properly.

If there is no spark:

A. Inspect all of the wiring.

 

B. Substitute another coil and test again. If there is now spark, the coil is at fault.

 

C. If there is still no spark, check to make sure there is 12 volts on the small Red wire from the MSD when the key is in the On position. If 12 volts are not present, find another 12 volt source and repeat the test.

 

D. After inspecting the test procedures and inspecting all of the wiring, there is still no spark, the Ignition is at fault. See the Warranty and Service Page for Information.

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 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. The diagram below 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.

Ford: Install the Diode inline 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. It is usually a Brown wire.
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 (See diagram below). This resistor will keep voltage from leaking through to the MSD unit.

Spark Plug Wires
If you suspect a spark plug wire to be open causing poor performance, check the resistance of each wire. By checking the resistance of each wire you will determine two things: That there is continuity (not open) and if there is too much resistance in the wire. Use an Ohm Meter and connect the terminals to the spark plug wire terminals. Use care to make sure there is good contact or the readings will be inaccurate. On MSD wires the resistance should be:

If you do not know the specification for your wires, measure the resistance of each wire. Remember to divide the length of the wire by 12 to get a "per foot" measurement. If one wire is out of that average spec, it is at fault

Solid Core Wires: You cannot run Solid Core Spark Plug Wires with an MSD Ignition Control. Solid Core wires do not suppress any Electro Magnetic Interference (EMI) which will interfere with electronics or rev limiters on your vehicle. A suppression style or spiral wound spark plug wire MUST be used.

Magnetic Pickup
in the Distributor
The magnetic pickup in MSD Distributors can also be checked with an Ohm meter to make sure it is within operating specifications. Once again, connect the Ohm meter's leads to the two terminals of the pickup. The resistance should be within 400 - 1,300 ohms. If the resistance is out of this specification, inspect the condition of the wires leading to the pickup for abrasion, shorting or opens. If the wiring is okay, the pickup is at fault.

NOTE: The Ignition will check good if the pickup is at fault. Follow the Checking for Spark procedure.

Timing Fluctuations
If your timing seems to be jumping all over the place, check the following items:

• What kind of timing light are you using? Many lights have trouble reading the MSD's capacitive discharge multiple sparks. Dial back timing lights are not recommended. Try another non-adjustable light and check the timing again. MSD offers a Timing Light, PN 8990.
• Make sure you are not using Solid Core wires.
• Inspect the routing of the Magnetic Pickup Harness. It should be routed clear of the coil primary wires and plug wires. It is best to route it along a ground plain such as the firewall, frame or engine block to form a shield around it.
• Check the polarity of the magnetic pickup wires of the distributor. Reverse the connectors and check the timing again. The correct polarity is whichever connection gives the most retarded timing.
• On Chevrolet engines, if the timing is retarding 10 - 20 degrees inspect for cam-walk. This is especially prevalent on engines with a chrome or stock timing chain cover that is actually bowing forward allowing the cam to "walk".