Gas Tank Breathers

[chbracke]

Well, I have the same issue that a few other guys have had which is that I've got a new tank in my '70 K5 all hooked up and functioning properly but I don't have the charcoal canister setup at all and when I fill up, I get gas spilling out from underneath the truck. My issue is that the breather lines are way too short (like about 12" each) and so when gas gets going out of one it pretty much has a siphon effect and keeps on pouring. I want to solve this by running longer vent lines but I'm not sure where to run them to (where to mount the other ends) and what breathers to put on the ends of them. Anyone willing to post a few pics of where their gas tank vent lines bolt up to the frame or elsewhere? Any ideas would be much appreciated!

[A1971Blazer]

Do you have this set-up at the rear on the opposite side from the fill neck?


My '70 has this but also has about 4 or 5 rubber lines directly below it under the bed.....I filled it up and gas started pouring out...all of the rubber was dry rotted and cracked. I replaced them and that stopped the leak(s).I do have the EVAP canister but I still haven't figured out what all these lines are supposed to do?

[chbracke]

That's an interesting looking apparatus, If I had to guess I'd say it has to do with the EVAP but it'd be just a guess. All I've got coming out of the tank other than the filler tube, sending unit wiring and fuel lines are the vent/spillover tube that runs up to the gas filler inlet and then a breather on both the drivers side and the passenger side.

[A1971Blazer]

For sure........I've been to two world's fairs and a goat f***in and I've never seen anything like it....
I suppose that some '70s had an EVAP and some didn't....I always thought that the pollution stuff didn't really start until '72......? but I've been wrong before..

So which line is the fuel coming out of?
I would tend to think you need some kind of rollover type vent...

this is interesting because I'm getting ready to fab myself a larger tank with an EFI set up.....
I'm not sure if I need to retain that jungle gym back there or just get rid of it..?

[hemi43]

Yeah, I learned something new too ! My 70 doesn't have those vent tubes on the opposite side. My vent tube exited right by the filler neck, which would make the tube about 3 feet long. I tried to post a pic but couldn't find one, sorry.

[4oldcars]

My 71 Jimmy has a replacement tank installed by PO. Don't know what filler neck was used. I put new rubber vent lines which run to a "collector" next to the filler. Four lines in, one line out. A single line would go from there to the front canister under the battery which I do not have. The single line goes thru the floor and stops. It is open and clear. It takes forever to fill the tank because I must run the gas pump at slowest possible rate or it clicks off. I hope this info is helpful to someone and if anyone knows why mine won't take gas, I'd like to know. I suspect the filler neck?????

[Glenco]

Funny I am just getting to this part of the project also and my hard lines to the vent stack on the drivers side are all rusted out. Has anybody had problems with just running a vented cap and plugging all the other vent tubes except for the filler tube breather??

[hemi43]

Originally Posted by Glenco

Funny I am just getting to this part of the project also and my hard lines to the vent stack on the drivers side are all rusted out. Has anybody had problems with just running a vented cap and plugging all the other vent tubes except for the filler tube breather??

That's exactly how they come from the factory when there's no emission controls, vent pipe and fill pipe.

[Glenco]

Thanks Hemi43 I wasn't looking forward to replacing all those steel lines that had rusted out on me!

[hemi43]

Originally Posted by Glenco

Thanks Hemi43 I wasn't looking forward to replacing all those steel lines that had rusted out on me!

NP !! Just remember to run a vented cap.

[bigdon-70blazer]

Never saw that on my 70.