Pressure is building up in my gas tank after a period of time. So much was built up that when my father took the gas cap off, while the car was parked and running, quite a bit of gas rocketed out of the tank like a geyser. I replaced the fuel pump last month because it was clogged with pieces of rubber from the old pump. The new pump is making a similar whining noise, so it's unsure if that too is clogged, or if it's another issue. But what I'm wondering is, if the tank is becoming pressurized because of my crappy tires. I picked up some used crappy 33s off Craigslist. I got them balanced, and found out there's a knot in one, causing shaking when I'm driving. It's quite bad. Could that be shaking the tank, causing the pressure? My tank also has a dent in it, but I'm sure it's been there since I've owned it. I'm putting my MTs on tonight to get rid of the crappy tires.

 

I do not understand how tires could cause a pressurized gas tank. It seems like a clog in the vent line, but then it would probably not allow gas to be sucked out, enless the pump is strong enough where it can push fuel out, suck air in (to replace missing fuel) but air cannot flow air out ... IDK! lol somethings gotta be clogged.

 

Well the tires are crappy, and when I drive down the road or on the highway, the truck shakes side to side. There's a bump in one of the tires. And wouldn't that shake the gas tank, causing more pressure? The old pump's rubber nipple deteriorated and there are chunks of rubber in the tank, so I wouldn't be surprised if something is clogged tbh.

Thanks

 

A gas tank isn't like a can of soda, shaking it isn't going to build pressure.

I'd say there's a problem with the gas cap or vent line. Get a vented cap. Problem sounds like the fuel tank is sucking the gas from the tank, but since there is no vent, it's sort of like if you put a straw into a plastic bag and suck the air out - it collapses, right? Well, your gas tank is strong enough to not collapse, but when you take off the gas cap, air suddenly rushes into the tank, at the same time the contents in the tank are being forced out.

 

When my Honda was low on gas it and when I would go fill it up it would make a pressure sounding noise. I couldnt tell if was sucking in or blowing out . Now he stated that it shot gas out, so wouldnt that mean its pressurized of forcing out.

Def seems like a clog though, I am intrigued with your tire shaking hypothesis but I cannot see it be deemed a theory <--sounded pretty smart huh? lol

-Mike

 

replace your gas cap. they fail and dont allow venting. also make sure you hear the clicks when you tighten. I once opened my tank and got 6 gallons to the face and chest of hot gas :-)

 

I thought the gas caps were non-vented.....the tank vents thru the EVAP system, no?

 

That is what I thought. It does sound like the vent line has collapsed or is plugged. And NO, bad tires making your jeep shack will NOT cause you tank to pressurize.

 

Where exactly is the EVAP system? I was told it's a charcoal grey box, with a bunch of lines going into it. I couldn't see anything from a quick glance. I have a 92, so it's possibly it's been removed by the previous owner. Just don't know what to look for in place of it.



Also, feel kinda stupid because I solved what was causing my issue. Ready for this? I had to redo my exhaust over the weekend because my u joint driveshaft broke, broke my muffler from my cat, and then once the shaft was fixed, the cat fell off. So I threw on some pipe to put it past the doors, then a glasspack to muffle some noise. Well turns out I forgot where the glasspack was pointing.. Yeah, about 6'' from the tank. The plastic cover is melted. I planned on adding a tailpipe, just couldn't get to it at that moment. Getting the rest of the pipe is now on top of my list, lol.


Thanks for the help guys. Do I have to pull the fuel pump out and inspect it? Since I was pretty much boiling the tank?

 

I KNOW THIS ONE!

Trust me on this......

Double double double check the vent tube coming OFF the Transfer case and make sure your gas tank evap hose is NOT, I repeat NOT connected somehow to that tube!!!!!! physically visually check the two hoses running from the top of the tank , they will go into a T-section then into a hard line running along side the driver side frame next to the brake and fuel lines. then it will come up at the firewall and then go to a rubber hose across the engine at the fire wall, then make sure it goes into the canister.

Mine was like this for like 4 years before I got tired of the gas smell in the cab after i got below a half tank. and decided to check it out.

it turns out when i had the clutch slave cyl replaced ( long story there but it is what it is), they connected the gas tank evap hose to the xfer case vent and the charcoal canister line that it is supposed to go to was left off.

check my other post on this issue for verification (search my username)

"gas smell in cab" or sumthin like that.

good luck an let us know what you find.!!!!

cpnwrench

 

Thanks for this! Turns out my new exhaust system I setup over the weekend was pointing at my gas tank. Heh.

 

my bad, you fixed it.

charcoal canister is just left of the dipstick on the 4.0L

cpnwrench

 

Oh OK, it's under the hood. Would've found it eventually.


And since I'm already at this point, I'll go over what you posted just to check it.



Thanks again!