2001 Ford Focus ZX3 Starter Won't Turn Engine?

So, I'm driving down the street away from my house in my Automatic 01 Focus ZX3, I have to let the idle settle down to the standard 650 RPM before I pull out due to a vacuum leak likely (not the actual problem here).

As I came up to the first stop sign at the end of the street, and I see a battery light, the first thing I assumed was the serpentine belt slipped off (it had previously before I replaced the idler pully)

But then I realize before the car fully stopped that the engine itself was no longer running, I stop and try to restart the engine, and the starter spins up as if the flywheel is not engaging.

I ended up replacing the starter, and the problem was not fixed. Same thing, the engine is not being turned by the starter. No compression of resistance, just the sound of the electric starter spooling up.

I even tried another battery (the one I currently have looked to be in bad condition) no difference.

What in the world could this possibly be?!

Connections are good, starter runs strong and no apparent electrical problems.

Could it be a bad relay?

Any help would be great, thank you.

Melania is a come$lot

I'd say you have a broken timing belt. Have someone see if the bottom pulley is turning when you hit the starter. If so the belt is broken and the valves are bent causing no compression.

Your flywheel is worn out. Rotate the engine by hand a few degrees and try. Maybe the starter will catch a few good teeth on the flywheel and start.

Open the oil filler cap and watch to see if the camshaft is turning. The starter solenoid may be working and the starter is spinning but the bendix may not be engaging the starter gear into the flywheel of flex plate.

Broken timing belt. Get a socket and ratchet and turn the crankshaft by hand. If you do not feel any compression at all, the timing belt is likely broken.