Gas tank gurgling noises

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I have a new charcoal canister installed. I did notice that today, on a very hot day the gas cap did release a small bit of air pressure. After shutting down the truck
I hear these gurgling sounds coming from the gas tank. I looked underneath and can hear the sounds coming from the gas tank. It sounds like there are large
air bubbles in the gas tank. The sounds continued for at least 10 minutes even after I removed the gas cap. It sounds like never ending air bubbles in the gas
tank that isn't stopping.

What could this be?
Where would I troubleshoot it first?
If I didn't hear the sounds, I would think the truck is running perfect.
 
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Boiling gas, pretty common.

Excessive fuel tank pressure
GeoRoss: Thank you for you insight and response to my post. From the link you sent me the pressure build up appears more common than the boiling gas sounds. As my charcoal canister is new, it's not likely the problem, although I've read on the posts that replacing the charcoal canister only resolves the pressure build up, not the boiling gas. Is there nothing I can do about the boiling gas?
 
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GeoRoss: Thank you for you insight and response to my post. From the link you sent me the pressure build up appears more common than the boiling gas sounds. As my charcoal canister is new, it's not likely the problem, although I've read on the posts that replacing the charcoal canister only resolves the pressure build up, not the boiling gas. Is there nothing I can do about the boiling gas?

Boiling gas is essentially the over pressure thing just to different degrees. Changes in the temperature of the gas and elevation change are prime drivers with the gas mixtures we get today. A new charcoal canister may help some people, but there is also a one-way valve from the tank to canister that could be at fault.

Lots of people have had this problem and tried to solve it. Some have solved it and others haven't.
 
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The better the charcoal canister vents, the lower the pressure in the tank, the more likely the ethanol-gas mixture is to boil. An old clogged up canister that produces high tank pressures might increase the boiling point just enough so its not noticeable.
 
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I have a new charcoal canister installed. I did notice that today, on a very hot day the gas cap did release a small bit of air pressure. After shutting down the truck
I hear these gurgling sounds coming from the gas tank. I looked underneath and can hear the sounds coming from the gas tank. It sounds like there are large
air bubbles in the gas tank. The sounds continued for at least 10 minutes even after I removed the gas cap. It sounds like never ending air bubbles in the gas
tank that isn't stopping.

What could this be?
Where would I troubleshoot it first?
If I didn't hear the sounds, I would think the truck is running perfect.

Did you replace your canister with an oem unit or the autozone unit?


A lot of the times when my tank would over pressurize I would get boiling noises, not everytime but a lot of the times.

I replaced my charcoal canister with the auto zone one and it did nothing to fix my problem. I don't believe the auto zone replacement is any good for our cruisers. Maybe they work for people in moderate climates and close to sea level but it didn't change a thing for me in Utah.

Than I vented mine to the atmosphere. No more boiling gas, pressure in the tank, and my fuel efficiency showed a noticeable improvement.

Goodluck
 
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The better the charcoal canister vents, the lower the pressure in the tank, the more likely the ethanol-gas mixture is to boil. An old clogged up canister that produces high tank pressures might increase the boiling point just enough so its not noticeable.
As per my original post, I have a new autozone canister installed.
 
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Did you replace your canister with an oem unit or the autozone unit? Autozone type


A lot of the times when my tank would over pressurize I would get boiling noises, not everytime but a lot of the times.

I replaced my charcoal canister with the auto zone one and it did nothing to fix my problem. I don't believe the auto zone replacement is any good for our cruisers. Maybe they work for people in moderate climates and close to sea level but it didn't change a thing for me in Utah. I never had this problem in the heat of Los Angeles. Now I'm in Northern Colorado.

Than I vented mine to the atmosphere. No more boiling gas, pressure in the tank, and my fuel efficiency showed a noticeable improvement. I have no routing tube on the bottom of the canister

Goodluck
 
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The Autozone canister still most likely has a vent on the bottom "cap" of the canister. The version I installed had a cap on the bottom, then I modified it to accept the factory hose.

You are now at 5000 Ft elevation. The boiling point of E15 gasoline is much lower at elevation than at sea level. (Water boils at 203°F at 5000 ft elevation, not 212°F)

Ethanol fuel makes it worse, so run a non-ethanol fuel (if you can find it). There is a check valve in the fuel system and you may need to replace that (I'm not 100% where it is). Also try a higher octane fuel, as it takes more energy to cause it to burn (IE evaporate as well) it MAY help reduce the gurgling.

Edit:
The bottom edge is the "vent cap" for the "factory drain hose". I removed the cap entirely and drilled it so my factory hose would insert and drain out through the fender. This is kinda unrelated to your boiling issue.

1658264980140.png
 
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The Autozone canister still most likely has a vent on the bottom "cap" of the canister. The version I installed had a cap on the bottom, then I modified it to accept the factory hose.

You are now at 5000 Ft elevation. The boiling point of E15 gasoline is much lower at elevation than at sea level. (Water boils at 203°F at 5000 ft elevation, not 212°F)

Ethanol fuel makes it worse, so run a non-ethanol fuel (if you can find it). There is a check valve in the fuel system and you may need to replace that (I'm not 100% where it is). Also try a higher octane fuel, as it takes more energy to cause it to burn (IE evaporate as well) it MAY help reduce the gurgling.
Good tips. I'll trying the higher grade octane.
Do you know the name of this fuel line check valve part?
 
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Check Valve for EVAP

1658265486458.png




Also consider changing the Fuel Pressure Regulator, as I vaguely recall someone having a similar issue. Please research before throwing parts at it, as I understand the FPR may not be the culprit.
1658265632904.png


1658265711640.png
 
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FPR P/N 2328075010

Check Valve P/N (still checking)
 
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As per my original post, I have a new autozone canister installed.
Do you know the P/N?

I used the VC120 on mine and don't have this issue, even at elevation. (I did get tank pressure, a little at elevation)

I'm asking because there may be a variance in manufacturers and which one we are using if there is an incorporated check vavle.

Upon scouring the Partsouq and McGeorge sites, the 96 does NOT have the Check Valve for EVAP shown in the diagram. That goes up through 01/1995.
My truck (08/95) apparently does not have it (I have not looked)

Now, I'm not sure, but it may point more to the FPR since it is gurgling back to the tank and there is a direct fuel return to the tank from there.
 
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Do you know the P/N? No, I can't see it on the part and I threw out the box it came in, but I'm pretty sure it's an Autozone canister like yours.

I used the VC120 on mine and don't have this issue, even at elevation. (I did get tank pressure, a little at elevation) I have had it installed for about 3 months and this is first time the gas cap released pressure I could hear. Usually, I hear nothing at all.

I'm asking because there may be a variance in manufacturers and which one we are using if there is an incorporated check vavle.

Upon scouring the Partsouq and McGeorge sites, the 96 does NOT have the Check Valve for EVAP shown in the diagram. That goes up through 01/1995.
My truck (08/95) apparently does not have it (I have not looked) That's awesome. Thank you so much for doing that research. I have a 96.

Now, I'm not sure, but it may point more to the FPR since it is gurgling back to the tank and there is a direct fuel return to the tank from there. That's seem like an inexpensive fix. I could change that out anyway.
 
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