Just what is this gray box just below the right side B-piller above the right rear tire? What is it's function?

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Archie's Choptop conversion #11, #15, Redux & The Stealth

[This message has been edited by madcurl (edited 05-08-2005).]

if you're talking about the triagle thingie above your left thigh, it's for emmissions.

Fuel expansion tank. Keeps your fuel from overflowing onto the parking lot on a hot day after a fillup. (I think)

PS - Tell the guy not to grind on it

[This message has been edited by ryan.hess (edited 05-08-2005).]

quote Originally posted by buddycraigg: if you're talking about the triagle thingie above your left thigh, it's for emmissions.

Yep, this it. What does it do for emissions? I seen it while removing my rear clip but I didn't have time to check were the connections ended up at? I know evaporation canister is location on the left inside near the original air filter.

quote Originally posted by madcurl: That doesn't sound right? Possible explosion if hit, right? I thought that the expansion over-flow was located on the gas line. It looks like a long metal tubular line.

That's the vent line... Basically when the fuel is underground, it's at like 50 degrees..... Fill up your car, and you have 11 gallons in your tank. Park it somewhere on a hot day, and that fuel will get to 70, 80, whatever degrees, and the fuel will have expanded to say, 11.3 gallons... but you only have an 11 gallon tank... gotta go somewhere.

yes - do NOT hit that tank. It will have gas fumes all ready to burn.

[This message has been edited by ryan.hess (edited 05-08-2005).]

Thanks. I didn't know that. It's a little scary now that I know.

[This message has been edited by madcurl (edited 05-08-2005).]

My '85 GT didn't have one. Interesting.

They didn't incorporate that expansion tank until later years....

Some more specific information on that tank. Yes, it is an expansion tank. On the '84-86 cars with the smaller tank the tank itself had an air bell at the top to allow for expansion. This is neccessary to prevent thermal expansion from pushing liquid fuel through the vapor line to the charcoal canister since if that happens even one time it ruins the canister. One of the things done to the '87-88 tank to increase capacity was to move the air bell function to a separate container, the one in the above picture, thus allowing the full volume of the tank to be dedicated to liquid gasoline.

The vapor recovery system is part of the emission control systems of the car, and it actually benefits the car owner because it allows the capture and reuse of fuel that would otherwise evaporate away, wasted, into the atmosphere. As fuel prices continue to spiral up this feature becomes more and more valuable.

JazzMan

What Jazz said....

The evap canister is on the left strut tower. Most people have no idea of how much fuel they would loose over time without it. Depending on weather and other things, you can loose the equivalent of a few tank fulls over the life of a car without it.

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurasic Park)

The Ogre's Fiero Cave (It's also at the top of every forum page...)

Question: What about for those who have changed over from a 84-86 to a 87-88 gas tank? Do they know about using this wonderful and yet important little item? I know Mr. Fiero has changed over to a 87-88 gas tank. I asumming if the steps are skip'd would cause issues, right?

Jazz - is this air bell you mentioned visible in the pic below. I always wondered why the later tank required expansion room but not the earlier tanks.

If not where is it located? Thx.

quote Originally posted by madcurl: Question: What about for those who have changed over from a 84-86 to a 87-88 gas tank? Do they know about using this wonderful and yet important little item? I know Mr. Fiero has changed over to a 87-88 gas tank. I asumming if the steps are skip'd would cause issues, right?

I would bet that most who switch to the later tank skip that step. A few years ago when I came on this forum people swore the bigger tank wouldn't fit the earlier cars. Then people realized that the later tank isn't really bigger and started swapping. It wasn't until recently that I started hearing about this expansion tank. So the art has evolved to where people know what the real deal is and can swap in the whole system if they want to get it right.

quote Originally posted by jscott1: I would bet that most who switch to the later tank skip that step. A few years ago when I came on this forum people swore the bigger tank wouldn't fit the earlier cars. Then people realized that the later tank isn't really bigger and started swapping. It wasn't until recently that I started hearing about this expansion tank. So the art has evolved to where people know what the real deal is and can swap in the whole system if they want to get it right.

Strange? That's what I heard too. That the 88 tank needed to be messaged into place. That was one my main reasons for not getting a 86 GT was due to the tank size. So it would be reason to believe that by not using this expansion tanks could cause issues down the roard or worse....a fire bomb?

With changes in temperature, the fuel in the tank expands / contracts. There always needs to be enough free space in the system to allow for expansion - if the fuel expands and is forced out the vent line it'll saturate the evap canister and render it useless.

In the earlier Fieros, the tank / filler design made it so you couldn't fill the tank completely; there was always enough air space at the top of the tank (unless someone got carried away with topping off the tank) to allow the fuel to expand safely.

When they increased the capacity of the tank, part of the increase came from a slightly larger tank that would still fit in the same location - and part of it came from using that air space to hold even more fuel. The GM engineers added an expansion tank to provide the neded air space and located it in the right fender area.

If you've got the larger 12 gallon tank, you need to have this expansion tank installed and connected. And if you've got this tank in your car, be careful if you work around it - it's normally full of gasoline vapors.