Fuel tanks / Cells - Aluminum?

[Alxj64]

Okay, so I've started to reach the rear portion of my Carryall and before I get too fancy with my last rear cross member build I'd like to have my fuel tank designed. I've done some measurements and it appears I can get about 28 gallons out of the shape I am looking into building without the tank hanging down super low under the truck.

I have access to (2) 4'x8'x1/8" Aluminum sheets, a 4' wide sheet break, and a TIG welder. My neighbor kid is actually the best TIG welder in his crew working on and repairing the hover-craft at the Navy Seal facility (Little Creek Amphib Base) and he is the one that will more than likely be doing the welding for me.

Obviously the tank will be supported with straps and not tabs.

What should my reservations be about building such a tank? I know that a few people have said to go with stainless and go with a thinner gauge. While building the tank, how should I plan my pickup? Should it be a sump type? I don't have the body on the truck at the moment either and I want to plan my filler neck to where it doesn't have to finagle through the inside of the body like the stock WC53 tank filler neck was, even if that means creating an indent or recess in the tank side or something.

Anyways, who has what advice, experience, suggestions? I'm all ears.

[Desoto61]

A sump would be nice since diesels hate sucking air, but could compromise the clearance you are aiming for. It would think it more important if the tank will set such that fuel would move a lot if the truck goes off axis, i.e. long and low vs a shorter taller tank, and how low you let the fuel needle get. Mine doesn't have the sump but I tend to not let it get below 1/4 tank if I can help it so it should be OK, plus since 1/4 tank is about 10 gallons.

When looking into the tank for mine one of the things Cummins recommended was that the return line and the suction be as far from each other as possible to minize airation, it would probably also help keep the fuel cool.

The other consideration will be baffels, where and how many depending on the size and shape to help prevent fuel sloshing.

Don't know about the Aluminum vs stainless debate though, plenty of tanks made out of both.

[Alxj64]

Yea, I am thinking a square grid for baffles that don't allow much sloshing around at all and doing just the corner triangle cuts in each baffle.

Few more questions.. Should the return line attach to a tube and be submerged to minimize aeration? Kinda like a beer keg tube? I figure return hose will go adjacent to the filler neck inlet since thats where all the aeration will happen even during a fill-up event and the initial restart to leave the fueling location... so put the pickup point near the opposite front corner. I've been trying to think of a way to install a water sight glass at the low point in the tank in an effort to help collect moisture. I've already had some bad experiences with water in diesel and water in gas so that being the case I'd like to be able to slide under the truck and purge the low point after the truck has been sitting.

Venting? What kinda of venting system should I look into for expansion, contraction, and vapor recovery? Are most diesel systems sealed and become pressurized? I hooked up my fuel cell in my Jeep trail rig a little wrong and as the tank sat in the sun it started to expand and flooded my shop floor through the vapor recovery canister. So that the diesel tank isn't sweating everywhere, is there a diesel vapor recovery system out there?

[Desoto61]

Diesel doesn't really evaporate like gasoline, it's the fuel that burns not the vapor, so I don't know that you would need a vapor recovery system, though most of those are (at their simplest) a filter canister (charcol and cotton type things) plumbed in line so fumes are captured and/or neutralized and then sucked back in when the system is running. Something could probably be done.

A water seperator in-line should do the same thing without as many fabrication issues. A boat supply site might be a good source for options, boats do a lot of custom diesel tanks that would have those kind of fittings and options.

The stock filler tube was the vent path on the trucks, so I plan on just keeping it that way, some have a small breather tube in the top of the filler pipe to help prevent vapor lock while filling.

My return line is inside the tank, it is a 1/4" threaded fitting on the side of the tank that connects to a tube that runs to the bottom of the tank and now that I think on it it is on the same side as the filler which is opposite where the fuel pickup is located.