I've been interested in this since the posting in the 911 section. Some time ago we saw a guy at a rest area that a vice grip on a broken line but still fuel sprayed everywhere. Guess it would depend where the line broke at but fuel was still everywhere. Total mess under the hood. Then after reading Dropley's 911 post got thinking about it again.
My kid when he helps me, when priming he just unscrews a fuel line at the bottom of vp pump. I thought maybe plugging off the broken line would help. Somebody else said no, a cap plug wouldn't be strong enough. Somebody else said don't plug off pump, bad for the pump. Then another members fuel line broke. I asked that member if he would mail me his broken line. After I get a broken line going to take it down to where I get my fittings and see if they can make something that would be a temp fix that you could screw in till new part comes in.
Mean time of the question of whether plugging off a hole in vp is OK for a short time to get off road or maybe until a new line is available is setteled in my mind. I'm not going to plug off vp if I ever do break a fuel line. I contacted several places. One place said plugging a hole would create unequal pressure inside the vp on what they called the pump head. Another place said the timing would get messed up and never work right again without rebuilding vp. Another place said no problem.
Anyway...my next step when I get an old fuel line is to see if anything can be made to have in tool box ready to go. Neighbor in the pressure washing business has couple machines that have massive psi. Pressure washers use flexible lines so maybe I can get something rigged up, to have handy.
I'll post my results after I find out if I can get a "temp" line rigged up.