Vacuum gas tank

BangkokDean

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Mar 25, 2008
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Hi when I remove the gas cap I hear a woosh sound? I am thinking it is caused by the charcoal canister/engine vacuum. Can i just remove the vacuum hose from the carburetor to the can, just leaving it off so the venting to the gas tank is still there just with out the vacuum connected?
 
It's vapor pressure in the tank. It's normal

You right for setting in the Florida sun with a non vented cap.....I have a vented locking cap now a daze.....and no issues...

thing I don't understand is like for my '72 that float valve should not be blocked, should be open to the line into the charcoal can.....why don't it release pressure there IF the tank is less than completely full.....I have had pressure there with the tank completely full, the float closed, and nowhere for the fuel to vent with the temp changes....

All I know is the car seemed to check out on the lines/canister ok....

:hissyfit:
 
Hi when I remove the gas cap I hear a woosh sound? I am thinking it is caused by the charcoal canister/engine vacuum. Can i just remove the vacuum hose from the carburetor to the can, just leaving it off so the venting to the gas tank is still there just with out the vacuum connected?

That's what I have done with both my 75 and 77, never any pressure in the tank and never noticed a smell. Those tanks had two vent ports, one for the steel tank and bladder and one for the bladder tee'd on top of the tank. No valves at all.

Try blowing thru the vent line to the tank to see if it's clear.
 
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