Never ran across this before. I’ve put three tanks of gas in the truck since I bought the truck. I went to fill up and when I started to unscrew the gas cap I was surprised the amount of air escaping. I know there’s always a small amount that will escape but there was so much pressure that the cap popped off once it got unscrewed enough. Literally popped off into my hand. I’m pretty confident it’s not normal for the tank to pressurize this much. Do I need to replace the charcoal canister? Clogged?
Abnormal air pressure in gas tank
- Thread starter bulax99
- Start date
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See the following thread. There are lots on this subject.
Replace your Charcoal Canister ASAP. VC120
forum.ih8mud.com
Replace your Charcoal Canister ASAP. VC120
Excessive fuel tank pressure
forum.ih8mud.com
A lot of us are having this issue, ethanol blend gasoline seems to make matters worse. Look up land Cruiser Phil's fix so far I have the best luck going this route
Charcoal canister, I found a thread that recommended a cheap GM one you can find on Amazon that's a good enough replacement. 5yrs and no problems since.
Tried that it did not work for me.
inkpot
SILVER Star
Mine does it with and without ethanol gas. So I just crack the cap enough to let pressure out, put my card in the pump, push all the buttons, pull the nozzle over to the rig, remove the cap because all the pressure is gone, and fill the tank. Not rocket science.
Glad that works for you. When I’m wheeling at high altitude the pressure builds so bad that the gas stinks without loosening the gas cap you can hardly drive in the car. If you open the gas cap it’ll literally spit gas out at you
Change your gas cap. If it’s 20+years old he vent in it is also clogged. This plus new carbon canister.
^^^^^^ x2
The gas cap vents both ways (or should) to help maintain proper pressure.
The gas cap vents both ways (or should) to help maintain proper pressure.
Just as an FYI the caps on these trucks do not have a vent in them. Because of CA. and federal emissions requirements vented gas caps went away decades ago. The cap used on our trucks have a one way valve on them that allows air to flow in as fuel is used other wise the tank would collapse because of vacuum. All the fuel fumes inside the tank are supposed to be dawned into the charcoal canister, held there until a valve under the intake opens, and draws those fumes into the engine to be burnt.
In the state of Arizona part of the IM240 emission test is to test you're gas cap to make sure that the cap ONLY allows air into the tank ,not out. If your cap allows fuel fumes to vent out you'll fail the test and not be allowed to renew your car tags until you replace your gas cap with a new one.
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If replacement is not an immediate option, I've found Oil Eater on a q-tip shoved into the top ports of the canister can help. There are two check-valves in there that are the usual culprits. Mine were thoroughly frozen. A few dips of the q-tips and an overnight sit seemed to loosen them enough to function. It's been a few months since and no further tank pressure/fuel boiling issues. Otherwise the VC-120 route is probably the most succinct resolution, despite the bolt length refit.
I vented mine directly for a while, fumes were intolerable, replaced with the VC120 and have been happy since. I still have my OEM unit in case I get bored someday and want to repair it, but its so low on the priority list it will be a long time.
There should be ZERO pressure when you remove your cap on a 80 series. If you have pressure either your canister is bad (see below) or the line from the tank to the canister is clogged.
forum.ih8mud.com
forum.ih8mud.com
I put an end to my Charcoal Canister problems for good!
In the past I rebuilt my canister but recently the problem popped back up and once I experience a problem 3 times I change directions and look for a final fix. The canister has 3 lines - 1 - comes straight from the tank with a one way valve at the canister < the problem 1 - goes to the VCV...
forum.ih8mud.com
Charcoal canister rebuild - 80 Series
80 Series Charcoal Canister rebuild. Bench grinder removes the seal cleanly. Wrap up is clean the valves, replace the old charcoal, button it up and reseal. You can weld it closed or use a good epoxy like JB weld. I will finish mine up later today with a little rattle can paint. The problem was...
forum.ih8mud.com
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MoJ
Moderator
Not sure “zero” is accurate. I’ve owned a number of new vehicles and they all let out a whoosh after driving on a hot day.There should be ZERO pressure when you remove your cap. If you have pressure either your canister is bad (see below) or the line from the tank to the canister is clogged.
I put an end to my Charcoal Canister problems for good!
In the past I rebuilt my canister but recently the problem popped back up and once I experience a problem 3 times I change directions and look for a final fix. The canister has 3 lines - 1 - comes straight from the tank with a one way valve at the canister < the problem 1 - goes to the VCV...
Charcoal canister rebuild - 80 Series
80 Series Charcoal Canister rebuild. Bench grinder removes the seal cleanly. Wrap up is clean the valves, replace the old charcoal, button it up and reseal. You can weld it closed or use a good epoxy like JB weld. I will finish mine up later today with a little rattle can paint. The problem was...
MoJ
Moderator
Do we know an 80 didn’t let out the typical “whoosh” when new? Is the system designed differently than all others?
