86Z

iTrader: (4)

after i shut my car off you hear noises from the gas tank like fuel boiling or filling up, it only last for a short while, wondering if this is normal?

UgotSmoked

it is normal...it does that when it get real hot outside, no worries, its normal. My suggestion is tinting ur rear window! and if it happens again, open ur gas tank and let some pressure out, you will notice when you take the cap off that heat waves are seen comeing out of the tank, because its so hot.

coolguywalt

You sure that's normal? Every other F-Body I have ever owned has never done that. My IROC does the same thing. I can barely make it home from work as I start smelling the gas. It still does it even with a full tank o' gas.

gmgod

I think the charcoal canister being clogged causes this. After a long trip in my vert, I shut it off and heard what sounded like a freakin steam cannister about to explode coming from the back of my car. I cracked the cap and released a LOT of pressure, scared the crap out of me.

MattODoom

iTrader: (1)

weird the UFO under the car should release pressure once it gets passed a certain point.

8T9 BANDIT

used to happen to me all the time,, just relive the pressure from the gas cap.. mine stopped after i had a leak and they removed my tank boiled it out and welded it,, i guess when they put it back in, they bent up the stem and its all messed up now.. but i guess it works almost like a breather now..

3.8TransAM

Wrong the UFO is a fuel tank vent valve it lets air in to replace the gas used.

Nothing is released from our cars vapor wise if everything works properly.

Either the FTVV isnt letting air in or the purge is not working correctly.

later
Jeremy

BADMAN

iTrader: (13)

I have been having a problem with my fuel pump starting to whine after driving for a short distance. Could it be the purge canister is plugged up or not venting to the throttle body as it is supposed to? If possible, could someone explain exactly how this system works in conjunction with the fuel tank? Also, if not working properly, can it cause the pump to whine because of excessive pressure in the fuel tank? BTW, pump and sending unit are new with a complete boiling of fuel tank. Did not mean to jump to another issue on this thread but I think it could be related. Thanks, Badman

xlwhellraiser

iTrader: (1)

Had this for a year with my vert. You guys should get under your car and touch the gas tank after you are done driving it. I am almost sure that your tank will be HOT. Hot to touch even (in some situations). I don't think the tank is suposed to be that hot.

I found that the rear end emmits some serious heat as well. The exhaust under the tank does not help.

It sounds weird, but go under your car and check it out.

8T9 BANDIT

are u saying there is a solution?? or do you want us all to scorch our hands

rockit

iTrader: (3)

yea i'm going through this as well and here are my conclusions: the fumes coming out of the tank aren't that hot, i recently hacked off my muffler to see if it was baking the fuel tank and nata, now that the muffler is off the car i can here the fuel bubbling after shut off even better. i think it my partially be temperature and charcoal canister operation, but i think its mostly in the return lines pushing that last bit of fuel pressure back into the tank causing a bubbling.

i'm replacing the charcoal filter in my camaro's canister, and putting the whole works in the GTA in hopes of eliminating this and picking up a mpg, infact come to think of it, if the charcoal canister was plugged and was just filling up with air, could that concievably cause a lean cruising condition? i've had problems with this car getting too hot on the highway only, not around the city at all only at 50 mph and above, goes away if i go about 80 sometimes.

one last thing, i see this come up in the tpi forums alot, but i can't recal it ever happening in the TBI forums, something to think about

xlwhellraiser

iTrader: (1)

Well, all I can think of is that the gas tank gets pretty damn hot. Now, how and why I guess I don't know. I know that the muffler is really heating it up, and I am re-locating it, by going with 1 pipe straight out with a cherry bomb glass pack (Ya, ya I know).

You guys should seriously look at the rear differentials. They get hot and the tank is sitting right above. I am pertty sure thats one of the problems.

Also, the reason charcoal canister is filling up is because there is too much pressure. The question is why there is too much pressure. Heat is one of the main culprits. On top of that we are all running systems with high pressures to begin with.
If you look at the system its actually easy to trouble shoot, however I am always stumped as to why its doing what its doing.

The charcoal canister has a line that goes into it from the tank. If the charcoal canister is filled with fuel than you have NO restriction in that line. Thats for sure. You can look at the vacum diverter thats really close to the canister. But if the fluid is coming through chances are that it works correctly. The purge valve might not be working, so after driving unplugg the line that goes to the throttle body from the canister and if there is fuel there or fuel smell than purge is working.

On the tank side, take the vent UFO Looking thing out and blow through it from both sides. If it lets air through with some work, than it works correctly. It is designed to hold 1-2PSI of pressure.

Now, thats pretty much it for the evap system. Looking at the rest of the system we have a sending and return line. The two lines are bound to get hot because 1 the exhaust underneath, rear end under the tank, lines go on the pass side rail and they share a mounting point close to the transmission which tends to get hot (I went touching my car when it was hot LOL), than exhaust heat also affects the fuel going towards the engine. When we get to the engine the fuel lines run by the hot heads, and than go the fuel rails under the TPI where they are heated nicely. Than they go back through the return line which follow the same pattern and the same heat. Now, is there any place for it to cool down. About 2 feet after the transmission and before the rear end (where the fuel filter is). Everywhere else the fuel is just being heated up. So, I am not sure how to keep it cool other than shielding the lines from every type of heat.

I've seen wrap around heat shields especially for fuel lines. It makes good sense to me. We need to figure out how to cool those suckers. I think thats the problem. HEAT.

Wheel Spin

There is "supposed" to be a heat shield betwen the muffler and fuel tank. Considering most of out cars have needed a new fuel pump after all these years, or a different exhaust has been installed, the heat shield may not be doing it's job, if it is even there.

xlwhellraiser

iTrader: (1)

Yup, mine is there, and I am running the EDELCRAP SDT exhaust 3inch. Even wrapped with header wrap it still heats up HOT HOT.

Will be cutting the muffler off tommorow. That little bitch.

However, some of you guys that are having problems, check if the heat shield is there.

rockit

iTrader: (3)

don't waste your time i went that route alllready, all you get is a car so loud you can't hear the bubbling anymore, i have the heatshield and it's not exhaust related

the209bnr

i have the same issue FML

camarosrock1989

iTrader: (1)

86Z i am going to give you this link because most of us have had this problem and are really frustrated with the no real answers. Just about the time someone thinks they have resolved it..WRONG.....Yeah... here you go, read until your brain just wants to explode..hahaha
https://www.thirdgen.org/forums/tpi/...regarding.html

freshZ28

Did you find out what was causing this ? Same is happening to me. I know its not supposed to do this, I've had plenty third gen not one has done this.

86Z

iTrader: (4)

not really, i just put on a vented gas cap.

IMissMy86TA

aren't our caps supposed to be vented? I have a low mile with original cap and I also have to let out pressure at the cap if I have been driving it a while and it whistles if I don't so I assume it does release pressure over time.... After opening the cap the whine goes away.

TylerSteez

iTrader: (3)

My car had extreme tank pressure for the first time yesterday when i was filling up the tank, then today when i shut the car off the fuel tank was making thunderous sounds. I have replaced my whole cooling system trying to figure out an overheating problem (still runs pretty hot) and now i have this problem. I just bought a new purge valve and filter for the charcoal canister. is there any other parts i should be looking at replacing on the evap canister? i have read that vented gas caps only let air in and do not release tank pressure, is this true?

ZZ42Fast

iTrader: (2)

Be great to know what we can do to solve this. Anyone?

Bob88GTA

iTrader: (2)

No answers here. My 88 has done it since I drove it off the showroom floor.
This issue will be around for a long time.
I DO know that after a drive and engine is shut down, that noise from the rear is the little valve at the axle making the fluttering/moaning sound. Remove cap, pressure/vacuum is gone.

IDK, sure keeps it interesting!

RBob

iTrader: (1)

High pressure in the fuel tank? It is the job of the CCP system (EVAPORATIVE EMlSSlON CONTROL SYSTEM (EECS)) to control the pressure in the tank. The '88 FSM for the TPI shows that the in-tank pressure control valve should open at 1" Hg (5 KPa), which is about .5 psi. So the tank pressure should not be higher then that.

This valve is part of the sending unit. There is also a restriction in the vent line to the CCP canister. If any of this fails or gets plugged the result can be high fuel tank pressure.

It looks like this is easy to test. If I am correct applying a small level of vacuum 1 - 2" Hg to the tank vent line should open the valve and prevent the vacuum from going any lower. To do this disconnect the tank vent line from the CCP Canister and apply the vacuum to that line.

RBob.

ZZ42Fast

iTrader: (2)

Thanks, sounds good. I will check that CCP- tank line