Mouse chewed wires, fixed,then turn key slowly it would start, some wires hanging below dash, van cleaned, vacummed, wires bumped, now turn key and no crank.
Seems likely that a wire or connector is loose or broken or corroded, or a fuse has blown (or possibly several). Could also be a faulty clutch interlock switch or powertrain control module or gear position switch or starter relay or keyswitch or starter solenoid/motor.
Use information from service manuals, on-line forums, circuit diagrams etc. to help you identify what wires and components to check, it will usually be a lot quicker and easier than randomly checking every circuit. Search for things like "1999 Plymouth Grand Voyager starter relay" and "1999 Plymouth Grand Voyager fuses" and "1999 plymouth grand voyager repair manual pdf".
If you have a test light or meter you can check for power into and out of the fuses, relays, keyswitch, etc. Follow the faulty circuit through to see where the power stops. If you're not sure how to do this find someone who does and ask them to help you. Concentrate on the circuit you are trying to fix (e.g. starter circuit). Use the wiring diagram for your exact model. If the correct wire colours are marked it can help a lot with identifying the wires you want to check.
Note that wires can sometimes change colours when they go through a connector.
Or just try the following:
If you can, find the relay that clicks when the key is turned. Relays can be unplugged so you can unplug them one at a time to see if clicking stops. Identify what the relay does
Check particularly if the starter relay (in relay box near battery?) clicks when the key is turned to start. If it does then the fault is after that (in the relay contacts or the starter solenoid/motor or the connecting wire).
**** Disconnect the battery earth (-) while fixing wires **** to avoid shorts.
Check for blown fuses, particularly the starter fuse (under the dash). Check for loose or corroded fuse connections.There are also some bigger fuses and some relays near the battery that should be checked.
Note: If a fuse has blown it is quite likely that there is a reason, e.g. something may have shorted out when bumped. Fuses rarely blow for no reason. If there is an exposed wire that hasn't been found, it's worth finding before it touches anything when you least need it.
What is a small problem at this stage could potentially turn into a much more expensive one (sparks, smoke, lots of money).
Don't try a bigger fuse !
Check for broken wires.
A cleanly broken wire should be easy to find.
It's a bit more tricky if a break is hidden inside the chewed insulation. If the wire bends easily at a spot it could be broken inside.
Even trickier if a wire has broken off at a join. If you look carefully enough you can usually see where a wire has broken from.
Don't guess if you can't be sure where a wire goes.
Joining the wrong things together leads to zero fun so be careful.
Mouse wee is highly corrosive and can damage wires /connectors. Unplug and carefully inspect the metal surfaces of the connectors for signs of corrosion, black or burnt appearance, or tarnishing. Clean or repair any damage.
All connections should be clean, tight and well insulated.
Good luck.