i friend gave me a sumpro tach that has 4 wires. i read the directions and it says to put the green wire to the negative wire of the ignition coil. I read the other post about which wire it is and I have a white wire with a spade connector the isnit hooked to anything. i was wondering if that is the negative wire.

1990 GMC Jimmy 5.7l.

 

Guess what I did.. I typed
how to wire a sunpro tach
into a google search box

It's the illum wire.
Black gnd,... red hot with key on.. grn coil neg

IF YOU ARE SMART.. you will read this
http://www.tradervar.com/All%20Other%20Sun%20Tachs.pdf

And find a fuse that is hot in run and crank. That way the tach will bounce while you crank it showing your ignition primary is working ok.

Be sure to hook it on the fused side..

 

i now green wire is coil neg. I am asking which wire on the coil is the negative one.

 

Guessing that you have a HEI distributor. The ones with the coils built into the cap.

Right next to the power wire for the coil there is another terminal that is for the tach.