fuel sending unit question

[78 K-10]

ok so i just got my gas tank dropped and noticed something. the middle line which i think is a 5/16 vent line is like 4 inched long. it doesnt have a plug on it. just open. do i need to put a plug on it ? btw it was way easier dropping the tank by undoing the 8 frame bolts holding the mounting plates for the straps than undoing the straps themselves!

so plug the vent tube or not... thanks guys

 

[78 K-10]

or is it a special spring loaded cap? check out the pic on it.

http://www.chuckschevytruckpages.com/fuel.html

 

[78 K-10]

pic of vent line

heres a pic of vent line

 

[crazy4offroad]

It's definately a vent line, needs to be plumbed up with a vent cap on it at least, they used to be connected to a charcoal canister.

 

[bucket]

I don't know when they starting using the charcoal canisters. When I dropped the tank on the '77 K5, that vent line was just a short hose with a breather stuck in it.

 

[78 K-10]

hmm well i just replaced it open to the freakin air. thats the way it was and i didnt want to have some weird vaacum created.. thoughts?

 

[thaifighter]

the cap is the same one on diff vent lines it is the same as an open line but the design stops crap IE bugs, water from getting into the tube it isnt spring loaded it just rattles