running fuel lines. I have a few questions

[daniel_buck]

yea, it's no biggie, just amazed at how many different fittings there are!

I've got a cap for the return line (in black!!) on order, a 90 degree -08an female adapter (in shiny metal!) and -08 male to barbed 1/2" adapter (in blue ) for the vent hose on order. I'll figure out what combination of adapters will work to get the -08an to 1/4" rubber hose tomorrow night. haha


So just out of curiosity, which way does the vent need to work? does it primarily need to draw fresh air in? (as the tank level gets lower) or push vapors out? (as it fills up, sloshes around, and what have you). A combination of both I guess, eh?

[inVERt'D]

I know what exactly you're talking about, and I don't have it all figured out myself. I just had to use the Van Gogh reference.

The vent works both ways to handle pressure differentials caused by heating and cooling. If not for that I suppose it would mostly work to draw air in as the tank emptied.

[daniel_buck]

Maybe this is a silly question, but how is this any different from the factory fuel tank? It doesn't look like it has any vent on it, just a line out (from the bottom), and a similar type of fuel level sending unit and a screw on gas cap. Other than that, it's basically just a steel box. The cap doesn't look like it has a vent on it, maybe it just doesn't seal perfectly, so that in itself is the 'vent'?

[inVERt'D]

Good question, really. The cap will allow it to breath. Newer vehicles have better sealing threads on the cap and a one-way valve which allows air in but supposedly don't let fumes out. If there wasn't a vent system of some kind, a vacuum would form inside the tank as fuel was pumped out. Inevitably this vacuum would overcome the pump's suction.

[daniel_buck]

I bet the cap just doesn't seal all the way. haha! Nice and safe

[inVERt'D]

I believe you're correct. Give us a test!

[jonah]

Those old caps definitely don't seal. If you ever wheel with early CJs you know as soon as the passenger side goes up the gas starts spilling out of the cap. Looks like you are on your way to a solid set up!

[daniel_buck]

Now that I think about it, yea if I would fill it to full, I could smell fuel leaking a little bit from the cap area for a day or two as it sloshed around until the fuel level went down a bit.

[jonah]

I was looking around at fittings and it does look like it is a two adapter deal. It looks like the easiest might be an AN to NPT adapter:
http://www.jegs.com/i/JEGS-Performan...ductId=1284108
then you could use commonly available NPT to barb fittings. Maybe not super pretty but it would work.

Otherwise you have to get from -8 to -4 series 400 (barbed hose end) and I don't see an easy path

[daniel_buck]

Yea, thats essentially what I have on order. It'll work I suppose. I just snug them all down, and they shouldn't leak. Then get a good hose clamp for the barbed fittings. I'll run soft line straight down to under the tub, then run hard line all the way to the engine bay.

[jonah]

You shouldn't have any trouble with it. Yours is a low pressure system so it is hard to go wrong. The only type of fitting I have had trouble with is a compression fitting I tried to use going from my hardline to a barb fitting. It eventually cracked the hardline. Now I have steel line with a flare to barb fitting on the end of the hard line, although you could really just slip the rubber line over the hard line and clamp it with no worries.

[daniel_buck]

I was just frustrated that there was no way to do it without stacking adapters, seems redneck, but I guess it's how you're supposed to do it, haha!

I'm just going to slip the rubber hose over the hard line, and clamp it. Maybe slip it farther and use 2 clamps, just for shiggles.

[jonah]

Yeah a nice female AN -8 with a 90 degree bend and -4 barb would be perfect....

Oh well, it is just the fuel system, no biggie - lol!

[daniel_buck]

I think I ended up with a 90 degree -8AN Female to female, -8an male to -6an female, and -6an male to 1/4" barbed. lots of different colors there, but it'll work, LOL I couldn't fine a -8an to barbed, straight or 90. had to step it down to -6 first. oh well! Just got a little bit more expensive though. suprises me how expensive these fittings are. I guess probably because they are overkill for my fuel needs.