No, don't suck fuel vapors into an electric-motor-operated device. All you need to do is have a short piece of fuel line handy that is folded over and held shut with a small clamp (or duct tape), and when you pull the old hose off of the steel line under the cab, plug it with your finger temporarily and then put the new blocked piece of fuel line on there quickly. After you get that plugged off, work on your fuel pump and other rubber line. Have a friend standing by and alert with a fire extinguisher. No smoking. Do the job outside. Here's another recent thread about fuel line.
https://67-72chevytrucks.com/vboard/...d.php?t=851223