MSD 7531 Troubleshooting Notes


Reference: MSD 7530, MSD 7531, TROUBLESHOOTING

MSD 7531 Ignition Box

MSD 7531 & 7530 Won't Fire / No Spark

In order for the MSD to fire, it has to have a power source and a signal from the crank trigger sensor (or distributor pickup). The notes below are in reference to a crank trigger as that's what most run on these ignitions.

  • No or low ignition power
    Verify you have at least 12 volts on the small red wire when Ignition is switched on.

  • Incorrect Crank Sensor Wiring
    Make sure and check that the Crank Trigger Sensor Wire is plugged into the correct plug on the MSD box. It should be plugged into the Violet & Green Two Wire Plug. If it's not, that would cause it not to fire. There are two, two-wire plugs on the MSD box, one is for the Crank Trigger (violet/green wires), the other is for a crank sensor (light blue/light green) which is not used. Verify you have it plugged into the correct plug.

  • Bad Crank Trigger Sensor
    A faulty Crank Trigger can prevent a MSD Ignition from firing. You can check a Flying Magnet Sensor by checking the resistance between the Violet and Green wires, it should measure 65-90 ohms Resistance.

  • Check Air Gap on Sensor
    Air gap on the Crank Trigger Sensor should be between .050 Min to .080 Max gap.

  • Manually triggering the Crank Trigger Input
    Make sure the ignition switch is off, take the coil wire from the cap and locate it so that it's about 1/2 from a ground location. You might want to hold it in place with something other than your bare hand! Use a clamp or weight to hold it in position. Next unhook the crank trigger pickup connector, turn the ignition on, and use a jumper wire to temporarily jump the green and violet crank trigger pickup wires together. Each time you jump those two wires you should get a spark. If you don't, it's likely your box is bad. If you do get a spark, then your crank trigger pickup is not functioning. It could be misadjusted, have a bad wire or be dead.
  • Manually Triggering with Distributor Pickup
    Make sure the ignition switch is off, take the coil wire from the cap and locate it so that it's about 1/2 from a ground location. You might want to hold it in place with something other than your bare hand! Use a clamp or weight to hold it in position. Next unhook the WHITE wire that goes into the MSD 7531 box, turn the ignition on, and temporarily jump it to ground. Each time you jump the white wire to ground, you should get a spark. If you don't, it's likely your box is bad. If you do get a spark, then your distributor pickup is not functioning. It could be misadjusted, have a bad wire connection or open, or the pickup could just be dead.

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