Elie changes from being a devout Jew who wants to be a Rabbi to an adult who loses his faith in God in a few occasions that I'm sure would change me and my faith if put in the same situation.
When the prisoners are hanged for stealing the soup and the one child suffers for that long period of time. Seeing that would make me think why would God make him suffer and not just let him die right away. Where is god is what I'd be thinking the whole time.
How Elie considers the starving prisoners stronger than God because Elie believes that God is weak for letting people of the earth suffer and for prisoners to be able to survive this makes them stronger than him. I would have to agree if put in the same situation, or I kind of even believe it now.
I though think truthfully that Elie keeps from allowing himself to die during the forced march because he actually is praying to god and trying to believe again.
That's just my opinion.
There are a few occasions that are stuck in my mind about what would make him change his faith.