Welcome to the CPL AGK question and answer forum. Please feel free to post your questions but more importantly also suggest answers for your forum colleagues. Bob himself or one of the other tutors will get to your question as soon as we can.
Q) If a heat soaked engine will not start due to fuel vaporization an appropriate action will be...
A) Operate the prime pump with the mixture in idle cut off to purge the vapor
The explanation in the answers section states that this will circulate cool fuel through the system and cool down the fuel lines. I understand that heat and low ambient pressure cause fuel vaporization but why would you put the mixture to completely lean? Wouldn't fully rich make cool the lines more?