# Pressure when I remove gas cap



## Spbeyond (Dec 28, 2009)

Hey guys, Noob questions here.

I only have had extensive experience with one vehicle before so Im not sure if this is normal. When I remove the gas cap on my hardbody there is quite the rush of air. I cannot tell if its going in or out. Is this normal? My POS mazda didn't do this. Im not sure if its related but sometimes when I stop the engine I can hear a buzzing from the fuel tank (fuel pump?) for maybe a minute after.


Also my stearing seems really loose.. Is there anything that can be done? Small bumbs send me veering lol.


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## zanegrey (Dec 5, 2005)

the lower the fuel amount the greater the pressure.. yes it is normal..

check steering components.

tie rod ends and ball joints.
but it sounds like bad shocks or you have looesned the torision bars...


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## CalHvyMetl (Dec 4, 2006)

Yes, it's normal because the fuel pump pressurizes the gas tank. I was used to Ford's fuel pump which pressurized the fuel line. So, I totally understand your confusion, and yes that's why your fuel pump runs even when the truck is not running.


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## NissanPartsDept (Mar 31, 2010)

The fuel pump does not pressurize the fuel tank and you should not be hearing a buzzing noise from the tank when the key is off.
It is normal for the tank to build up some pressure just from fuel expansion. However, there is such a thing as too much pressure/vacuum.
Try to determine where the buzzing noise is coming from. The cap? you may have a plugged carbon canister.


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## CalHvyMetl (Dec 4, 2006)

Okay, my mistake. I assumed that since this is the first vehicle I've owned that has a pressure rated gas cap, that it had a pressurized tank. So why has my fuel pump run without the key being on for the last 15 years? I thought it was tripped by a pressure switch, but I'm obviously wrong.


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## herrry.orason (Apr 10, 2010)

Check your evap fuel emissions canister for any plugged lines. The tank vents to this canister to trap excess hydrocarbon before its released to the atmosphere. Small dirt particles are all it takes to clog the system. A little hissing noise when the gas cap is backed away is normal from time to time, but the smell of gas, etc signals a plugged line or bad canister. Replace the canister.


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## zanegrey (Dec 5, 2005)

the lower the fuel amount the greater the pressure.. yes it is normal..

what did you do about the suspension ??


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## NissanPartsDept (Mar 31, 2010)

Yes pressure build-up in the tank is normal to a certain extent. If the pressure is building to the point that you are getting a buzzing noise from the tank area after turning off the engine, this is not normal and could be dangerous. Get it checked out.


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## zanegrey (Dec 5, 2005)

change the cap...


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