ok, here is my problem, when i have it hooked up, the engine wont start, when it's not hooked up the engine starts and runs just fine, when the engine is running and i touch the wire to the tach lead the engine dies. my dad says i have a short somewhere. i have no clue what the problem is...P.S. i'm installing this aftermarket tach cuz the in dash tach doesnt work anymore

 

sounds like you are grounding out the ignition. check all the wires you ran for the tach for shorts.

 

You have a short somewhere. What color wire are you trying to hook up to the tach lead? Green or white?

 

You must have a short somewhere like everyone else said. You gotta trace your tach wire & find out where. What happened to me one time was I uncovered some of the sheathing(is that how you spell it???) on the wire while going through the firewall. Hope you can solve it

 

i got the red going to battery, black to ground, white to swtiched lights and green to negative coil terminal, i'm fairly certain that there arent any shorts in the wiring cuz i soldered and heat shrinked all of my conections

 

are you running green all the way to the coil?

if yes, your tach is bad, if no, try it

 

i got the tach from a friends V6 camaro, i know that there are different setings for the I4, V6, and V8, the was a orange wire and a brown wire, and they were cut, my friend said those two wires should be reconnected for the V8 setting, how should they be?