[jhein]

Below is my post from a different thread. No testing for evaporation but with a Qjet filter in place and a RobbMc pump, I have no drain back.

"So about 2 weeks ago I decided to remove a RobbMc in line fuel filter that I had right before my pump after I realized that it wasn't needed since I have a sock on my pickup and the Qjet filter in place. I had to move the car before I did the job so I knew the bowl was full. When I removed the line from the pump, not a single drop came out. The next day when I went to start it, it fired right up instantly like always. So I don't seem to have any drain back. I believe it's just good old fashioned evaporation which in my environment with my fuel takes about 3 days after a hot shutdown. It's also likely that most of it occurs while the engine is still hot. With the hood down and the air cleaner in place it probably stays warm for quite a while. Once it cools down the process must slow down."