If you setup an empty vehicle in the editor and set the healthbar down to zero the vehicle always explodes (sound/smoke/fire), even when not fueled/armed.

It should be:
health/ammo/fuel
0/0/0 = burned out wreck without smoke, fire, explosion
0/0/1 = burning wreck with smoke and fire but without explosion
0/1/1 = just as it is now: fire, smoke, explosions

Intermediates could be handled just like either the full settings *or* set the time the vehicle burns/explodes/...