Engine won’t turn over

Hopefully you won't be missing a couple teeth on the flywheel. Your starter has a small gear at the end of a shaft. When activated, it meshes with the teeth on the flywheel which starts the engine. Often, when corrosion is present on the wires, that small gear pushes forward but does not retract completely. That is the 'grinding' noise you're hearing. If the wiring fails, the small gear will not activate, meaning you'll hear nothing. The starter should be removed and that small gear checked for damage. Also all the connecting wiring must be in good working order so check that as well. Whoever does the work should check the flywheel for any damage as well. Missing teeth on the flywheel doesn't necessarily mean it need to be replaced, but be aware there might be those occasions when the small gear on the starter tries to mesh with the missing part of the flywheel and your vehicle won't start. There's ways around that too, so if that's what you find, let us know.......Dennis