New Gauges won't allow car to start

[73Grande/Mach1]

I just installed a set of Auto Meter Gauges in my 73 coupe and went to to test them out and the car wouldn't start. After fiddling for a while I found that if I disconnected the the Tach signal wire that comes from the distributor it will fire right up. Has anyone ever seen or heard of something like this? Please help!

 

[gpierce]

Ignition circuit in original wired cars go through the tach so is that your problem? Grounding it when you connect it?

 

[Jeff73Mach1]

did you bypas the original tach circuit by connecting the two tach wires together and running a new signal wire for the tach?

 

[will e]

Did the car have the original tach option?

 

[jbojo]

did you bypas the original tach circuit by connecting the two tach wires together and running a new signal wire for the tach?

+1

If you installed a new tach with it's own power connections you will need to jumper the 2 original tach wires for the car to start.

 

[Don C]

Did you run a new wire from the tach to the coil, or try to use an existing wire? Either way, a short or ground is the most likely reason. #2 would be incorrect connections, #3 would be a faulty tach.

Because you said removing your tach wire allows the engine to start I'm assuming you didn't mess with the existing lead from the ignition switch to the coil, whether or not you had an original tach.

 

[B229218]

old thread, new reply. green wire w/red stripe from key goes through tach to coil, is also resistor wire behind tach bezel. ford tacos  are current, not voltage based. (also why m.s.d. boxes need tach adaptor to work tach) no tach, no no spark. run jumper wire at connector in loom behind tach to start car.