I'm a newbie here and ran into this forum while trying to figure out the following problem. Anyway, I'm in the process of restoring a 1966 Mustang (289 Cubic Inch, V8 Coupe, Automatic). I recently rewired it from bumper to bumper, but, I connected something wrong because now the engine turns on the first click on the ignition switch. I've traced the wiring from the battery - to the solenoid - to the ignition - to the starter, but, can't seem to find the issue. Any recommendations on what to look for to trouble shoot it? Thank you all in advance and I'm so glad to have becomed a member here. I've been crusing the forum most of the afternoon and I've learnt so much already. Thank you again!

 

Welcome to the forum. I know this may seem obvious, but could there be a SHORT in the Ignition Switch itself?

 

Yep, sounds like you've got your wires crossed at the back of the ign. switch. Use a test light and trace where you have juice at each key position.
Here's the schematics to help trace where the wires go:
http://hammar.dyndns.org/~djhamma/wiring/wiring1966.htm

Jon

 

This afternoon I changed the ignition switch out but with no luck. The switch was old, so your idea that it could be a short made sense. Needed a new ignition switch anyway cause the old one was already very loose internally. It was not expensive to buy another one. That's what I love about restoring the '66 Mustang, you can find many very inexpensive new parts at any auto stores!Thanks.

 

Thanks for the wiring schematics these will really help. Not to likely that I crossed wires at the back of the ign. switch, since most of the wiring is already pre-attached to connectors that you just plug into each other and only fit one way; including those connections to the back of the ign. switch. Plus, I bought all the wiring from Champion Mustangs which was all fabricated to OEM specifications. I'll definitely use a test light and trace where the juice is and see what I find. Again, thank you for the schematics those are great.

 

Check to make sure you don't have the "plug on" wires crossed right at the starter relay. Brown wire goes to the I term (most rearward) and the red-blue wire goes to the S terminal