When you turn the ignition and it clicks but will not turn over and the lights still work what could it be

The clicking you hear is probably the starter solenoid. You have ruled out a weak battery being the probable cause by attempting to the jump-start the engine right? In any case, this means either the power cable running directly from the battery to the starter motor is too resistive/poorly connected, or that the starter motor itself is no longer functioning. You don't specify how many miles are on the vehicle, but this is a real possibility. The failure of the starter motor could be due to the brushes making poor contact, since they wear each time the van is started.If you're willing, you can try tapping on the starter motor housing with a rubber mallot, a broom handle, or something similar while someone tries to start the vehicle. I was able to squeeze a few more starts out of my old starter this way. This would also pinpoint the probable cause to the starter motor, most auto parts stores will bench test a starter motor for you. Here's how to bench test a starter yourself........... STEP 1:The Circuit Descriptions alt="Bench Testing the Starter Motor">

To Bench Test the Starter you'll need battery jumper cables, a jumper wire, a working battery, and of course the Starter Motor out of the car or truck. These are the circuit descriptions of the photo above:

1. number 1: This is where the Start/Crank wire is attached to. When you turn the ignition switch to Start/Crank this wire delivers 12 Volts to activate the Starter Solenoid. This in turn makes the Starter Motor work.
2. number 2: This is where the Cable from the Battery is attached to.
3. number 3: The Grounding point. The Starter Motor is grounded thru' its case.
4. http://easyautodiagnostics.com/misc-index/starter-motor-bench-test-1

Suspect the starter solenoid or the starter itself. Taking voltage measurements while trying to start would be where I would go first. Also, check for loose wires or bad grounds in the engine bay between the battery, starting circuit, and chassis.

Low battery, battery cables not making secure connection, battery terminals oxidized or needing cleaning/brushing .... failed starter .... tap the starter with a wrench, it can revive it :)