valve who needs ajustment
dead battery
cv joints
A pebble.
cv joint or universal joint
clicking noise is probably fuel pump relay, check for battery condition, then for good connections including ground, inspect all fuses
if you have connected it up properly it could be just that your battery is completely flat and that when you hook up the charger some relays are getting power and making the clicking noise
probably just getting rocks caught in the tread.
Volkswagen Vanagon Official Factory Repair Manual Bently Publishers.com
you may have leaves in the fan
Because it cuts down the noise of the fuel exploding in the cylinder ! Without silencers, the noise generated from vehicle engines would be horrendous !
If there is a clicking noise get it to a mechanic you engine is blown and may be saved. Most likely you'll need a new one because a lifter is broken and it would be cheaper.
Bad CV joints