There is currently an issue with vehicles which use energy as power source currently start with 0 energy and do not gain any energy at all,

Examples of some vehicles with these problem include http://www.wowhead.com/npc=29647 and the drakes which players mount during p3 of Malygos encounter in eoe

Core revision fd753a6

Vehicles which use other types of power eg pyrite (demos in ulduar, heat cannons in icc) seem fine this is only effecting vehicles which use energy