I have a 1993 Miata that I bought two years ago. It ran like a champ for months and then began have problems starting when cold, not even turning over. I have replaced the starter twice, cleaned and replaced the ignition switch a couple times, installed a new clutch switch and the battery is good. Dash and head lights work fine and the starter cranks when connected directly to the battery. I do not know if there is an anti-theft device installed.
Please help with ideas on where to go next in this adventure
thanks

 

'roo:
Have you had a chance to do some voltage drop testing in the starting circuits?
Can you find out if it gets fuel and spark when you shortcut the starting circuit?
Have had chance to check the crank position sensor and the cam position sensor?

There should be a blinking light somewhere if it has an anti theft devise.

I am not sure if I am of much help but voltage drop testing will let you know where the juice goes and where it stops. That is the key to closing in on the problem.

Here is an article on voltage drop testing: Voltage Drop Testing

Good luck, mate!