I thought my starter was bad.
I didn't hear the starter clicking though...
It's a 1989 Tracker.
It's killin me. I rebuilt motor n every week since... I've had to replace injector, brakes, muffler, MAP etc etc

I did hear a weird click near the ECU.

I changed the starter and it still makes that one click.
Starter/solenoid makes no noise.

What the hell is down there making a click sound when I turn the key?

Thanks for the help

I can't help but wonder how many of those parts have been changed unnecessarily...

Failure to crank can be caused by several things - flat battery, loose/dirty or corroded battery connections, defective wiring, defective neutral safety switch (if it's an automatic), defective clutch safety switch (if it's a manual), defective ignition switch, defective starter (which you've already replaced).

Get a volt meter or at the very least a test light and verify you have the requisite voltages at the starter when you turn the key to start.

Since you say you've just rebuilt the motor, let me ask you this - did you remember to reconnect the ground strap on the bellhousing?