Energy absorber

Energy absorbers' is a vital component of Transformer anatomy that allowed them the capacity to refuel, presumably with Energon.

Generation 1 cartoon continuity
Starscream "neglected" to equip his newly created Combaticons with energy absorbers in order to control them. He told them to obey him and they would capture and remove the energy absorbers from other Transformers and equip them in the Combaticons.