[Paul Thompson 'Hooligan']

Hi Dave -

The tach output on the MSD gives one pulse per firing. So on a V8, it gives 4 pulses per rotation of the crank.

I would think your tacho is incorrectly set so check the settings or any configuration switches.

Out of interest, the 6AL tach out is open collector output, so can also be used to trigger an EFi system with a 5v input range if required. Neat unit - despite the fact that some say it means 'My Sparks Duff'.

One last thing, if the system is being fitted to a motor that already has other rpm triggered devices, shift lights etc etc, IF they are connected to the coil, their inputs will need to be moved to the 6AL tach out too. The MSD will give multiple sparks at low revs and also drives the ignition coil with a higher than normal voltage. This in turn will give rise to false triggering or can blow-up the input stage of 'normal coil triggered' devices.

(Hope that makes sense.... seems a bit convoluted when I re-read it)