Capped fuel line under vehicle?

[Fordman999]

Hey everyone I was just wondering what is this capped fuel line at the gas cap under the vehicle that also has the main fuel line attached to? I've had a problem for the last 6 months of my vehicle losing a lot of gas and I've done everything chech vacuum lines, change sparkplugs, check fuel injectors, check EGR, new manifold gaskets, new gas cap... And today I noticed there is a cracked line under vehicle right next to where you add fuel that is capped with a white cap that has a long crack. What is this "spare" line for??

 

[Turdle]

Please take a picture of this and post it back here

 

[Fordman999]

I just did some research and found out it is a rear differential breather tube that has some sort of air release if the pressure gets too high. It is capped of with some sort of platistic vent tube contraption.