Electric pump before or after mechanical

I am sure it is evaporating. After investigating, I noticed the pressure gauge shows nada. Pull the Carb top and the bowls are empty. Crank, crank, crank (5-10 secs) pressure comes up, 10 seconds later it fires.
I have checked backflow and cant find any. I believe when I shut down, the fuel in Carb evaporates, needle/seat opens, pressure bleeds into bowls and then evaps some more.
Not sure this is what’s happening, just what I have concluded from inspection/investigation.
I don’t really want to run an electric but not sure what to do about the issue.
Not going to buy a new tank for a return line. Mine already has the charcoal can return capped that I could use but what would that help? Won’t stop the pressure loss will it?
Not a tank this.....http://www.jegs.com/i/Auto-Metal-Direct/106/881-1468-3R/10002/-1?CAWELAID=230006180013542138&CAGPSPN=pla&CAAGID=44693592161&CATCI=pla-172937246471&CATARGETID=230006180039218457&cadevice=c&gclid=EAIaIQobChMIpYuGyIaT2gIVE1p-Ch3pHAVfEAQYBSABEgLywfD_BwE