MSD 6a Cranking but no spark issue driving me crazy.....


New Member
Oct 16, 2020
Hi guys,
Hoping you can help......
I’ve just recently purchased the MSD 6a ignition system and wired it in as per specs in the manual. The car was driving fine prior to MSD 6a ignition when 12volt ignition wired directly to the +coil and distributor wired to the positive+ and negative_ of the coil.

I’ve run into some problems trying to get the MSD 6a ignition to spark. Here is some information.
  • 1966 Ford Mustang 289
  • Rewired with painless performance wiring harness
  • After-market ‘bosch-style’ Distributor is an electronic distributor red and black wire (no amplifier)
  • Coil is a Pertronix Flamethrower 2 (0.6ahm 12volts)
I’ve wired in the distributor as per the MSD 6a diagram for an aftermarket magnetic pickup distributor
MSD wiring diagram.png Painless MSD wiring.jpg
I’ve completed the spark test by shorting the green and violet wires and confirmed spark.

There is no ballast resistor fitted to the car.

Using a voltage meter I can confirm 12volts at the small red wire going into the MSD 6a from the ignition switch in the ‘on’ position. At the ‘start’ position on my ignition switch the volts drops slightly as it cranks which I understand is normal.
I’m not getting any spark through the distributor. I can confirm the distributor is turning when I crank the engine.
Bosch style magnetic pickup distributor.jpg
I changed the magnetic pick-up in the distributor to a brand new one and confirmed it works.

I swapped out a the coil to a known working coil and still no spark.

I’m stuck as to why this is happening. Any ideas?
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Mark, This isn't what you are going to want to hear, but it is what it is. Take the MSD out of the car. Put it back in the box it came in and wire the car back up the way it was before you started. I had one on my car once. It was junk. In the two years I've been on this site I've seen several threads where people have the problems that you are having.

Is there any particular reason you are trying to use the MSD box? I dont think it really does much unless you are running a really hot motor.
Thanks Olivethefet, appreciate the honesty. I guess I was drawn into the claims of improved idle and throttle response. I've had my head under the bonnet for the last few days and can't make any sense of it. I've been reading threads for days and it's really difficult to find an answer to this issue. Looks like i may be taking your sound advice.......
You can check if the MSD6a is working by disconnecting the red/green wire going to the distributor and then (with the key on) use a jumper across the red wire/green wire. Each time that you jumper it it should make a spark at the coil wire (it will only spark once for each time that you make the connection. The output of the coil wire should be located just above (1/8") a grounded source, such as a valve cover. Of course the MSD unit needs to have both voltage and ground available to function.

The exact instructions for doing the above test are in the MSD manual.
The MSD box on my car has been the only reliable thing Mostly Starts Dammit has made. The rest of the MSD parts (the EFI system and coil) were junk.

That said, on a street-driven car that sees zero track time and most mild street/strip cars, they're wholly un-necessary.

You can use either a Ford Duraspark system (or a GM HEI module if you want to be sneaky and hide your more modern ignition system ) and be just fine.