where in the book do you see examples of Elie losing his faith in god

I don't think Eli ever really looses his faith. I recall many times in the novel when he certainly questions it.

-When the people are being lined up in front of the furnace he asks God how he could let this happen.

-In the camp an elder speaks about loosing faith and Eli wonders if God is even his "enemy"

-When angel faced Pipel is hanged in the gallows, Eli wonders where God is? Here Eli hears a voice in his head saying that God is also in the gallows.

In the end I don't think Eli forsakes his faith more than re-evaluates what he had been taught as a child juxtaposed to the Jewish holocaust experience.