pacerdonfl

Seem like there is excessive air pressure in the tank when I remove the fuel cap. Takes quite a bit of time to blow down.

I have another 91 LS 400 that seems much more normal in amount of pressure bleed down.

Besides that, it runs perfectly.

Any ideas?

Thanks,

/Don

Amskeptic

My '91 does that too. I crack the cap loose just enough to hiss, THEN go do my credit card swipe at the pump. Then, when I have successfully inputted my zipcode and selected my grade, it is ready to be removed. The warning on the cap is all you need to know that this is normal.
Colin

AlaskanLS

Replace your car's charcoal canister, the problem will go away.

deanshark

That's pretty drastic in my opinion.
Try this: http://www.lexls.com/tutorials/maint...capgasket.html It worked for me, and others.

Amskeptic

The gas cap seal must be intact to *prevent air escape*. The cap does have an air intake valve built into it only for times when the tank is about to go into a vacuum (as when it cools after a hot day).

At coolant temperatures above 129*F, the BVSV valve does NOT allow charcoal tank/fuel tank air to escape into the engine's intake when the throttle plate is closed. You will get a pressure release at the cap at fill-up. It tells you that the evap system is intact. If you never get an air release when you remove the cap on a warm day or when the engine is fully warm, that tells you that some hose in the system is likely leaking.

From the Owner's Manual page 38
"When opening the cap, do not remove quickly. Fuel may be under pressure and spray out of the fuel filler neck under hot weather conditions, etc., which may cause injury."

oldskewel

iTrader: (1)

I have always had a pretty good pressurized release of gas fumes when opening the gas cap. Never really had any negative effects on the car, except maybe in the brief period before replacing my almost dead fuel pump (but not sure about that one, since problems were intermittent, etc.).

And I'm in CA, where they check the vapor control system (including charcoal canister, as far as I know) every two years during the smog check - and I've always passed.

So I'd advise that doing nothing at all is a viable option.

deanshark

For some reason that link isn't working but you all know where to find it.....Lexls-tutorials-maintenance. But anyway, the gas cap gasket is made to release some of the pressure but when it's crushed it doesn't let any out. It should be changed every 6 years anyway, and it's cheap enough.

VolumeToo

So you have to input your zip code to buy fuel? Is this something everyone has to do all over the US? (WTF!)

oldskewel

iTrader: (1)

Zip code is common here in California, at least. It is a security thing - checks that the credit card billing zip code matches whatever you enter. Otherwise, stolen credit cards would be used at gas stations a lot more.

sha4000

iTrader: (1)

Inputting the zip code is pretty standard and good safety measure.

nthach

These cars don't have an ORVR system like "new" cars do to capture fuel vapors during refueling, and those usually have oversized charcoal canisters.

You're fine, the EVAP system on these cars are pretty primitive. Just be sure to use an OEM fuel cap if you need to replace it - the aftermarket ones aren't vented.