I'm renovating a 1983 Renault 4 GTL but broke the key off in the ignition barrel. I don't need security so I bought a push button start but it hasn't come with a wiring diagram. It has a toggle switch to turn on the ignition, then a push button to start the engine. I've got four wires that were attached to the back of the key barrel. The plate that the switches are mounted on is aluminium, do I need a separate earth? Any advice on how to wire it up would be appreciated.