Join Date: May 2017
Location: Ontario, Canada
I'll use the term modern loosely, but you are not entirely wrong. A return system will help, but it's the pressure from the pump that prevents the vapor lock. Most of the newest vehicles don't have a return line due to emissions. In the case of your Fiat, I'd bet that the pump was weak. The head from a full tank would help in that case we opposed to the cooling benefit from a full tank.
2017 Colorado Z71 CCLB -Graphite
Morimoto 2stroke 2.0 H11's, Sealight 9005's, Stark 5202's
Extang Encore tonneau
Rockstar mud flaps