How do you connect a tachometer in a 1993 Chevy S-10 2.8L?

green signal wire goes to the negative side of coil, not the positive.

On your tach you probably have a ground(black),power(red), signal(green) and illumination(yellow?) wires. The signal wire splices into the positive side of the coil. The rest of the wires are pretty self explanatory. Make sure you have a solid ground and power. The illumination wire can be hooked into the headlight switch so it goes on with your lights. Tim

The statement above is true for hooking up a tach. I just installed one in my 87 gmc s15. the trucks are set up from the factory to come with one, so you will find a wire located in the wiring harness that has a hookup for your tach. This is so you dont have to mess with the distributer set up. This may save you some time.