Based on your description, it sounds like you have a bad starter. Have you had it tested? What to try is this. See if there is 12v to the smaller wire on the starter when the key is in the start position. You will need a helper to do it. If there is, the main larger wire from the battery is clean and tight, and the battery terminals are clean and tight, replace the starter.
Here is a link that explains how to check the starter:
Here is a link that explains how in general one is replaced:
Here are the directions specific to your vehicle for replacement. The attached pics correlate with the directions.
2000 Plymouth Truck Grand Voyager V6-3.3L VIN R
Vehicle Starting and Charging Starting System Starter Motor Service and Repair Procedures
1. Release hood latch and open hood.
Battery Negative Cable
2. Disconnect and isolate the battery negative cable.
3. Hoist and support vehicle on safety stands.
Starter - Engine Wire Connectors
4. Remove nut holding B+ terminal to starter solenoid.
5. Disconnect solenoid connector from starter.
6. Remove bolts holding starter to transaxle bellhousing.
7. Remove starter from bellhousing.
8. Separate starter spacer from transaxle bell housing.
1. Place starter spacer in position on transaxle bellhousing, flange toward flywheel.
2. Place starter in position on bellhousing.
3. Install bolts to hold starter to transaxle bellhousing.
4. Connect solenoid connector into starter.
5. Install nut to hold B+ terminal to starter solenoid.
6. Lower vehicle.
7. Connect battery negative cable.
8. Verify starter operation.
Based on what you mentioned, it sounds like the solenoid is bad.
Let me know what you find or if you have other questions.
Images (Click to enlarge)
Saturday, February 22nd, 2020 AT 5:54 PM