I have had my msd 6a for about 3 years and have only put approx. 12-18K miles on the car since.
Heres the story, I woke up early to take my car to the alignment shop. started fine and everything but when I started down the street, it gimped -electrical like the ignition just cut out for just a second. I thought that was real strange but didnt think nothing of it. Then down the road a way it did it again, and I thought what the hell is that. so I got my alignment, (took 2 hours) and started numerous times at the shop, everything fine. Drove home and parked it. Then....... This evening I was going to go to lowes. NOT
Would not start. I checked all over the place, everything looks fine as usual. So I dig out my MSD 6A instructions and start troubleshooting.... It is hooked up by the purple and green (magnetic picup), it says to take coil wire and place it approx 1/2" from grounding spot, turn key to on position and then it says to jumper the green and purple together, and every time you break the short a spark should jump from the coil wire. ---so if spark is present then the ignition is working properly.

So I tested it and nothing...... no spark, then it says to check the small red wire for 12 volts with ignition in on position. Yeah 12v good to go there. then it says sub coil and repeat test. So I walk 1/2 hour to autozone and 1/2 hr back with new coil. Then I re-test with new coil - and bam- Got spark.... So then I retest with old coil -and bam- got spark there too.. so what the @#$%. So I put everything back together right, start the car and go for test drive.

idles fine, but half a block down it gimps, and gimps and gimps again. so I turn around real quick, and come back home. pull in the driveway and it gimps again. Put in park, rev it some - seems fine, turn it off. Then I go to restart it and wont start, no spark again.....

This is totally out of the blue, I havent touched anything that would even remotely have anything to do with electrical any time lately.

The distributor is also a newer MSD billet put it in about 2 yrs ago. it is not timing or carb related problem.

So my question is this -1. what is the lifespan of these msd boxes? (box is mounted on top of wheelwell)-------2. If it is toast, what is a good top of the line replacement w/rev limiter? ---3. why all the sudden die?

Any other tests I can do on coil or the box?
Thanks guys
Eric

To test a coil, try this. Disconnect the negative wire at coil. Temp install another wire on the negative side of coil with the opposite end of the wire stripped of insulation. Disconnect the plug wire that goes from coil to dist at the dist. Install a spark plug into the end of plug wire that you just disconnected and ground that plug against a good ground, ie engine block. Turn ignition switch on and take the wire connected to the coil negative and tap it against a good ground. If coil is good, it will spark with each tap. I'm gonna guess and say it's your MSD box that is toast. I've never had one last as long as you did. I switched to Accel 300+. The intermittent problem could be either the box or coil. Good luck.