So,, WTF am I looking at..?

[dyeager535]

I'd be hugely surprised if any fuel system is completely closed. You cant push or suck fuel out of a tank without letting air replace the liquid that is lost. Sooner or later the tank will collapse, or the pump will be unable to overcome the vacuum and fuel will cease moving.

Try sucking the liquid out of a plastic bottle (the bottle will collapse) or a metal one (nothing comes out). Same as trying to pull fuel out of a completely sealed fuel tank.

You can always leave the cap loose if it just has to run

 

[Big Ray]

Chevy ran 40+ gal tanks for years with just charcoal cans and vented caps...lord knows how many folks have remove the charcoal cans.

Work fine, last long time.

 

[skunked]

I was already thinking about that. Since the diesel tank didn't have vents, it had to have used a vented cap to let air in and not suck in the tank.
I still have the diesel cap in it lol.,

For this weekend I'm going to T them together, and run a hose out to the frame. Then plug it. Then I can get to that hose and do whatever if I have issues, without dropping the tank again.

You can always connect it to the vent like @Truckman4life mentioned.

Here's the setup on my 97 2 door as a reference.

 

[shady]

That's pretty much what I plan to do for now. I'm going to cap it and keep an eye on my fuel pressure though.
If my pressure stays consistent over time, I'll leave it that way. If not, I'll figure out a vent system for it.
Being a burb, and the fact that I'm going to drill holes in my floor to mount a few things, I don't want it venting under the body.
I've thought maybe the air box as mentioned, or even behind the front bumper. That's long term fix though.
At least I figured out how to plug the holes for the weekend. $40 over night shipped for the pair wasn't bad at all.

I knew posting here would help lol