When i remove my gas cap after running for a while there is a sudden rush of air like the fuel tank has + or - pressure. Is it supposed to have pressure in it? Could it be the charcoal canister in the engine compartment? Thanks for help in advance.

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1989 Iroc-Z TPI 350 auto 4-spd Removed MAF screens K & N filters, Hedman smog shorties, accel 8mm wires, mfu wire looms.

 

the vent isn't working properly, or your muffler is too close to the heat shield.

 

Which vent? The plastic one under the car by the gas tank? I don't think it is a heat problem but i'll check that to make sure.

 

Your fuel system is a closed system, developing some pressure in the tank is normal.

 

This is normal!

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89 GTA G92
305 TPI WC 5spd w/3.45
Accel Cap & 8mm Taylor's
Custom 4" Cold Air Induction
Jet Airfoil
K&N Airfilter
160 deg stat/fan switch TB Bypass - Steel Rad
Cat back 3" Exhaust w/Terminator Muff.
HiGh FlOw Dynomax Cat
Spohn LCA's - KYB GR-2's
Moroso Crank Bolt and roller pilot bearing.
Autometer Vac+Oil Temp

 

That is normal. The tank pressure helps the fuel pump anyways. The system does not vent the gas continuously,the charcoal canister solenoid opens when the vacuum is high such as when decelerating. Even then it does not draw all vapors out of the tank so there is still some pressure buid-up.
It is still recommended that you release the pressure slowly.

 

if your fuel tank vented to the outside air there would be no purpose the evap canister system which is designed so that vaporous gasoline isnt vented into the air.

 

Ok then I got one for you guys. For some odd reason, ever since I installed my Bosch high flow pump, the pressure gets so great that it starts to suck in the tank itself, go figure. I replaced the small vent, a new gas cap, the charcoal canister, even the valves that attach to the canister. Noone can seem to figure this out. Can someone try to explain. I'm running fuel at 47psi.

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88'TA 305TPI 330HP, NATURALLY ASPIRATED, PASSES N.J. EMMISIONS. "I AM JUST THAT GOOD"

 

your gas cap is probably not vented at all. I had to make mine vented by drilling a small hole into it on the inside and outside.

 

won't that leak gas out on your car? My car has the same problem. When I fill my tank up all the way I get lots of preasure and gas spills out on the side of my car. Not tons of gas but enough to cover the area inbetween the gas hole and the wheel well. I really want to figure out how to fix this problem.

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88 iroc
LB9 305 tpi
k&n, flowmaster, ADS chip
160* thermostat
home made ram air
removed smog pump
TB bypass
ASCD big block hood

 

your gas tank pukes because of muffler heat.

 

so do I need to move my muffler down some. Is there something that I could do to fix it because I think that where the pipes connect is rusted. Is there something that I can put inbetween them that would cool it down?

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88 iroc
LB9 305 tpi
k&n, flowmaster, ADS chip
160* thermostat
home made ram air
removed smog pump
TB bypass
ASCD big block hood

 

Your canister system should be able to keep the pressure down in the tank. If I doesn't, I'd just install a vented gas cap. It'll vent the pressure with no loss of fuel.

Jake

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1986 Corvette Coupe, 415 CID, Edelbrock 6073s, ZZ9

 

insulate your tank from the heat.

 

Also if you live in a smog state and your system is closed,they will check your cap with a vacuum unit.First time i saw it was this year. Mike

 

But I have a Stant vented gas cap and it still retains pressure. Go figure.

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88'TA 305TPI 330HP, NATURALLY ASPIRATED, PASSES N.J. EMMISIONS. "I AM JUST THAT GOOD"