The four wires should be the hot(constant 12v), ground, switched/remote(intermittent 12v), and the -/+ ignition wire(distributor wire for RPM's). This is the way I wired in my sun tach on my 79 chrysler 318. The only problem I had at first was I had the positive ignition wire instead of the negative. It causes no damage as the guage just goes the opposite direction. If it happens, switch the wires then you'll be good to go.