[Walt Fricke]

First off, study the circuit diagram (very simple) which came with your switch. With the big battery switch on, one of the little switches is also on, and one off.

The "off" one is the one you use connect the resistor from big positive away from battery to ground when you turn the master off. This is said to cushion the alternator going off, since it can't in a sense drain into the battery with the master disconnecting the battery - something like that.

Don't mess with the ignition.

The key is the switch which is on in when the master is also on, and off when it is off.

Run the DME relay black/white wire which connects pin 20 of the DME itself to the 85b terminal of the DME relay through this little switch. That way when you turn the master off, the fuel pump relay is de-energized, it opens, no current can flow to the fuel pump, and the fuel pump stops. You engine will promptly stop when the fuel pump stops.

Relay coils are low current devices, so they are what you want to turn off with the small switch. The fuel pump fuse is 25 amps, which gives you an idea of its current draw. Relays are made to handle that. The little switch under the master cut-off is not.