Testing a Car's MSD Ignition

Most of the problems with MSD ignitions are caused from poor grounds, to close to the exhaust or located in an area with little ventilation. Over heating is hard on the ignition. The MSD box should be located far enough from the exhaust so as not to absorb heat and in a well ventilated area. If inside the vehicle, it should be located under the dash in the open or somewhere where ventilation is not a factor. Do not install in the glove compartment.

Tools needed:
Set of ¼-inch drive sockets
¼-inch drive ratchet
Volt and Ohm meter

Step 1: Check the wiring at the MSD. There is a 10-gauge red and black wire, which is the primary power and ground. The large red wire should go straight to the battery or buss bar from the battery. Test this wire with the voltmeter for 12 volts with the key off. The large black wire is the main ground and should be connected directly to the engine. Check this wire with the ohmmeter. Test the black wire from close to the MSD to the engine block. There should be no resistance.

Step 2: Check the 16-gauge black and orange wires. The orange wire goes to the power side of the coil and the black to the negative side. Check these wires with the key off from the MSD side to the coil terminal side looking for a break in the wires. Use the ohmmeter and there should be no resistance.

Step 3: Check the 16-gauge red wire for power when the key is on only. Use the voltmeter and test for 12 volts with the key on. This is switched voltage used to turn the MSD on and off.

Step 4: Check the white 16-gauge wire for continuity to the distributor if using a point type distributor. Use the ohmmeter and check from the MSD to the distributor connection. There should be no resistance.

Step 5: Check the purple and green wires if using an MSD or Unilite type magnetic pickup ignition. Use the ohmmeter and check for continuity from the MSD to the distributor making sure there is no resistance.

Step 6: Check for a failed coil if all these wires are good and the MSD was getting power from the battery and the ignition switch. Use the ohmmeter and test for continuity between the positive and negative terminals. It should have no continuity or very little. Check the secondary resistance from the coil tower to the positive terminal. There should be between 6000 to 30,000 ohms. If not replace the coil.