When electric fuel pumps are installed to carby fed vehicles, they are often just connected to the ignition circuit to run whenever the ignition is on. This can be dangerous in an accident if the fuel lines are severed and the driver is not able to turn off the ignition for whatever reason. There are a number of ways to increase the safety of this setup, including inertia switches that cut the power to the fuel pump when a big enough inertia is caused by an accident. In this setup, we will sense the ignition signal and cut the fuel pump when the engine stalls. This device is based on a readily accessible Jaycar kit.

Items Required

• Jaycar kit KC5378 - Only available online
• Jaycar HB6014 or UB3 case
• 10mm tapped spacers and screws to mount the board to the case.
  
• Some extra wire

The kit and case were around $50 delivered.

Assembly

Assemble the kit as per the instructions.
Attach wires to 12v, Gnd, signal in, and two wires for one of the normally open circuits.


Mount the board to the lid of the box and measure up to determine where to drill a hole for the wires to exit.
Wire up the 12v wire to an ignition source and Gnd to a good ground source.
Break the existing fuel pump relay activation wire, and connect it across the two normally open circuit wires (the green ones in my picture).
Connect the input signal wire to your tacho input wire (coming either from your coil negative, or electronic distributor tacho signal).
You will need to adjust the pots on the board so that the fuel pump activates during cranking.

The finished product will look something like this:

This is a relatively simple and cheap method of putting a fuel pump safety device in your vehicle.
When the engine stalls and there is no more ignition signal, the fuel pump will be disabled.