Q. The Gemara in Brachos says be carful in the Tefilloh of Mincha because Eliyahu Hanavi was answered on Har Carmel by mincha.
I was wondering how is this a proof? Did he attempt to daven at other teffilos and was only answered by mincha?
In addition what exactly prompted him to daven so fervently? Didn’t he receive a specific command to build an alter from Hashem and thus knew he would be Matzliach?
Shkoyach

A. Meforshim explain that Eliahu chose tefilas Mincha so as to give ample opportunity to the Baal’s prophets to exercise fully their false believes. They served their deities mainly during the time the sun ascended until the noon. When they didn’t receive any response, it was the time of Mincha already, and he was answered at that time.
Horav Shlomo Miller Shlit’a pointed out, that although Hashem instructed Eliahu to bring the korban, He did not tell him that a fire would descend from heaven and consume it. That was Eliahu’s idea and choice of the portent and sign that would convince the people. He needed to pray fervently that Hashem should agree with him.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit’a