Why is my starter not working?

Good afternoon.

Is the engine turning when the starter is engaged? If it is then the Bendix is good. If it is not, then the Bendix has failed. the starter will have to be replaced.

These guides can help us fix it

https://www.2carpros.com/articles/starter-not-working-repair

and

https://www.2carpros.com/articles/car-battery-load-test

Please run down these guides and report back.

STARTER REMOVAL

Warning: when performing maintenance on the starting system be aware that heavy gauge leads are connected directly to the battery. Make sure protective caps are in place when maintenance is complete.

1. Disconnect the battery ground cable.
2. Raise and support the vehicle.

Warning: the electrical power to the air suspension system must be shut off prior to hoisting, jacking or towing an air suspension vehicle. This can be accomplished by turning off the air suspension switch located in the rh kick panel area. Failure to do so may result in unexpected inflation or deflation of the air springs which may result in shifting of the vehicle during these operations.

3. Remove the starter motor solenoid terminal cover

The 4.6L Engine Is Shown; The 4.2L Engine Is Similar

4. Disconnect the starter motor electrical connections.
1 Remove the nuts.
2 Remove the battery cable.
3 Remove the starter solenoid wire.

The 4.6L Engine Is Shown; The 4.2L Engine Is Similar

5. Remove the (A) starter motor ground cable nut and the (B) starter motor ground cable.

The 4.2L Engine Is Shown; The 4.6L Engine Is Similar

6. Remove the starter.
1 Remove the two bolts.
2 Remove the starter.