Thread: Fuel tank pressure

I haven't seen the new regs but the tank must have a vent somewhere to allow the pump to continue to pump fuel from it. Without it the tank will eventually have too much vacuum in it and the fuel pump will not be able to overcome it. I have no idea how it could create a pressure in it. Are you sure that was pressure to heard and not it sucking air into the tank as you loosened the cap.

Vent is 1 way, lets air in so it doesnt create a vacuum under use. They do not let air out when fuel expands so you do not have gas fumes in your bilge, the tanks can blow up like a balloon if needed.

Sent from my SM-A516U using Crappie.com mobile app

Bill... definitely out. Cap was going upward as I loosened it.

Sent from my SM-S711U using Crappie.com Fishing mobile app

Kevin... so you are saying that the pressure is expected and nothing to worry about?

Sent from my SM-S711U using Crappie.com Fishing mobile app

Yes exactly, thank Obama for that one when he changed the laws for gas tank venting. Removable plastic tanks can blow up like a party balloon without issue. Just never ever ever look down at or open a tank at eye level!!! Gas in the eye will ruin your day

Old school metal ones are open vent both ways. And mounted boat tanks have external venting both ways outside of the boat.

Sent from my SM-A516U using Crappie.com mobile app

So what actually happens with the old tank is that as the pressure builds up it is immediately vented......which is bad they say. With the new tanks the pressure continues to build and then you open the tank and let the vapors out all at once. Not sure what the difference is between letting out a little at a time vs all at once but somehow someone convinced the powers to be that it is........oh, and the tanks now cost TWICE as much.

I understand what is being said here but something don't make sense. If its normal for these newer tanks to expand is there a way to release that pressure so you can safely remove the cap for refueling? Kevin is right, you DO NOT want gas in your eyes.

Originally Posted by Barnacle Bill

I understand what is being said here but something don't make sense. If its normal for these newer tanks to expand is there a way to release that pressure so you can safely remove the cap for refueling? Kevin is right, you DO NOT want gas in your eyes.

The pressure is released as you open the cap, no other vent "outgoing". There is an "incoming" vent that is one way.