Anatomy of a gas tank

[fbnwest]

I am tinkering with my gas tanks, replacing lines and toying with idea of a different filler door. While I had the aux tank laying on the ground I realized (first time seeing it out of truck) that it had more lines out then I previously thought. This is a plastic tank, manufacturer unknown. It has the following;

Plug for the sending unit

Approx. 3 inch hose leading to the filler pipe

Approx. 1 inch hose leading to the vent pipe attached to the filler pipe

Small diameter line leading to the switch and subsequently the engine

and another line with what looks like a (busted) check valve at the end of it?

If this is as I suspect a line to vent the tank, then what is the purpose of the other line that connects to the vent (for lack of a better word) pipe attached to the filler pipe? Would I still need a vented gas cap with this line in place?

I looked but could not see the same on the main tank, it is still in the truck. Not sure I plan on doing anything other then put it all back in place like it was, but I always like to learn more about my bronco. So feel free to chuckle at the newbie and give me the intel.

Thanks

 

[Seabronc]

Usually the large one serves to vent the tank while filling it and the small line is for the evaporative emissions control system for helping to prevent the tank from over expanding when setting in the hot sun. In you case, since it is not an original tank, it may be redundant, but in newer vehicles it would go to a carbon canister to collect the expansion fumes and then be dumped into the engine when the vehicle is started up. A vented gas cap does the same function with the exception of the evaporative emissions system. I would leave it as a backup to the vented gas cap. That tank was probably a universal design so that it could be used with newer vehicles and meet current environmental laws.

Good luck,

>-

 

[Bully Bob]

Your sig. doesn't show a "year" for your rig... shows 196? ....

At some point, if memory serves., there was a charcoal canister in the system.

The stock tank is/was plastic.

--"Plug for the sending unit"--

Not sure what this means but, my guess is someone modified this tank.

The sending unit has the fuel pick-up tube attached to it, that runs to the bottom of the tank.

There's a large filler tube

A small vent tube

(that's 3)

On some, there's a 4th small ****** with a long tube into the tank with small holes in the tube. This., I believe went to the smog sys. or canister.

You could post a pic. or two for better advice.... /emoticons/[email protected] 2x" width="20" height="20" />

The Bronco stores have the stock tanks & all the piecee-parts to re-build your tank if there's no cracks or other leaks. It's a cheap investment & good insurance., since you already have it out. (their websites have pics of stock & aft. mkt. tanks, etc.)

 

[fbnwest]

By plug for sending unit I meant the 2 prong electrical plug that shows how much gas you have at the gauge.

My truck reads VIN as a 1970 but the grill is a earlier one with the small turn signals. All the body panels are aftermarket, think I made the sig when I was still trying to figure it all out.

 

[Bully Bob]

Ahhh..., you're lucky...!

I don't like the big fat turn signal lights.

It's likely, the grill is stock..as the later yrs., Ford just stuck a chunk-o-rubber on the back of the (bigger) light buckets. The holes in the grill were the same. Could be it just has the earlier light buckets/turn sig.

BUT., I think the *****-down brackets were diff.

Anyhooooo.., sounds like the tank is OK. I would leave that 'lil hose with the check valve on there as these tanks seem to vent too slow in stock form anyway.