Jumped tach and got shocked?
 

I have an MSD ready to run distributor, and I just had a shop install rally gauges in my car. The tach works fine. The rev limiter on the MSD distributor is set by grounding the tach wire. So, I went in and ran a jumper to the back of the tach (under the assumption that is where the MSD tach output is hooked to). When I picked up the jumper, I got the crap shocked out of me!

I really don't get it. Is that possible somehow if the tach was wired to the coil instead of the distributor tach output? Shouldn't the coil just have 12 volts?

As a side note, if anybody at MSD is listening, that is an awfully inconvenient way to set a rev limiter. Just sayin'.

On a regular points ignition system there is a very short positive voltage pulse on the primary coil winding that can easily reach 200-300 volts when the points first open. It'll bite you pretty good. I've never looked at an MSD system, but I'll bet you it is the same, if not more.

Yep, you will see (feel) several hundred volts on the tach coil connection.

George

good to know the problem is me and not the car! i had gone a good 20 years without being shocked, I had foolishly suspected myself of having gotten wiser.