Namo Buddhaya.
Craving is said to be the root of the fuel. Without fuel consciousness can not arise. However in the dependent origination craving manifests very late in the sequence of dependent originations. Consciousness arises at the 3rd step immediately after ignorance and volitional formations. But the fuel or craving arises after consciousness and feelings have arisen. Ideally first the craving should have arisen and then the consciousness should arise. This sutta explains how craving is the fuel for consciousness. As the sutta is very long I will quote some parts of it for better understanding.
Consciousness is described as "like a fire".
It’s like fire, which is reckoned according to the specific conditions dependent upon which it burns.
What is the fuel ?
In my opinion it is logically implied here that consciousness is fuelled by craving: because fire can not exist without fuel. And what is the fuel ? Craving. Simple.
“Mendicants, there are these four fuels. They maintain sentient beings that have been born and help those that are about to be born. What four? Solid food, whether coarse or fine; contact is the second, mental intention the third, and consciousness the fourth.
What is the source, origin, birthplace, and root of these four fuels? Craving.
When does Craving occur?
ignorance is a condition for choices. Choices are a condition for consciousness. Consciousness is a condition for name and form. Name and form is a condition for the six sense fields. The six sense fields are conditions for contact. Contact is a condition for feeling. Feeling is a condition for craving.
My question is : How can consciousness arise without the arousal of craving in the first place in the dependent origination ?