air bubbles in M51 plastic fuel line

[bigjuice69]

with the electric fuel pump running the plastic fuel line has air bubbles flowing thur it, but with the engine running the bubbles disappear if someone can help it would be great. thanks

 

[Westech]

Cavitation. When the fuel pump is on and truck not running thee is no place for the fuel to go. It just gets swirled around in the pump. With the pump on and truck running the fuel has a place to go.

Westy