Gas Tank PRESSURE??? Or Fuel RELIEF PRESSURE?? - JeepForum.com

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post #1 of 23 Old 04-09-2011, 04:01 PM Thread Starter
915kingwrangler
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Gas Tank PRESSURE??? Or Fuel RELIEF PRESSURE??

My yj has problem I havent been able to explain, evrytime I go and put some gas, when I unscrew the cap it sounds like all this pressure is built up in the tank and I can hear it release when I remove the cap, like alot of air coming out, also I have to hold the nozzle when I put gas, I cant just leave the nozzle filling like everybody else does when filling up, I have to press on it and hold it, I have only a ideas but not very solid on this...any jeepin help is appreciated....

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post #2 of 23 Old 04-09-2011, 04:08 PM
HurricaneRZA
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When you fill up, and you let go... Does it go *click* as if it was full? Then you have to hold it a little less than all the way to get gas in?

Always happened to me, don't know what it is but I dropped some of that fuel cleaner/fuel injector cleaner that I had in the garage in there. Hasn't happened since, I don't know if its related but that's what it did for me.

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I always get people coming over and saying things like "I wish I knew how to do that," etc- but they don't realize- at some point I didn't know how to do it either- I had to figure it out.
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post #3 of 23 Old 04-09-2011, 06:40 PM
terryjeep
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I have this problem also and although I don't know what causes it, I think safe to assume attention to fuel pressure regulator, fuel filter, or fuel pump is in order. I checked my fuel pressure and it was approx 10 psi too high. Hopefully we will get some answer from a more expert person.
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post #4 of 23 Old 04-09-2011, 07:17 PM
moonshinefuel
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Tanks have pressure release valves, and vent lines. Maybe a vent line is pinched somewhere on top of the tank, or another area.
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post #5 of 23 Old 04-09-2011, 07:55 PM Thread Starter
915kingwrangler
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Well the problem is that my fuel pump is less than a year old, I also replaced the fuel filter when I changed the pump, tomorrow Ill check all the fuel lines, it just seems strange you know how it sounds everytime I unscrew the fuel cap, you can hear this hissing sound like alot of pressure is in the gas tank..I know there is supposed to be some pressure ,but I mean when I put gas I have to hold the nozzle and press against the filler neck, like I cant just press on the nozzle and let it sit there filling my tank, if I dont press against the filler neck it just pops the nozzle out...this is the weirdest thing my jeep has done...
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post #6 of 23 Old 04-09-2011, 08:18 PM
moonshinefuel
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I was wondering if you had the tank out, the vent line is probably pinched against the body, on top of the tank.
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post #7 of 23 Old 04-09-2011, 08:34 PM
linusb
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it's normal to have some pressure and hiss. if it's excessive could be vent as suggested or your fuel getting too hot in tank. your exhaust routed properly?

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post #8 of 23 Old 04-09-2011, 09:38 PM
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Quote:
Originally Posted by linusb View Post
it's normal to have some pressure and hiss. if it's excessive could be vent as suggested or your fuel getting too hot in tank. your exhaust routed properly?
X2 on the tank possibly being heated up a lot from a bad exhaust routing.. on my old YJ I was running without a tailpipe for a bit and with the exhaust basically blowing straight onto the gas tank I had a TON of pressure build up in the tank.

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post #9 of 23 Old 04-09-2011, 10:36 PM
Krochus
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My YJ has just recently started doing this. Id been smelling excessive fuel vapors and when i stopped to investigate So much pressure had built up that the tank hissed for several several seconds after the cap was removed.

A basic check today confirmed that the vent valve was functional

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post #10 of 23 Old 04-10-2011, 01:13 AM
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Speak of the devil... mine did this after work today right when i got home (i wanted to siphon some gas out).
Just did the 15 gal to 20 gal conversion to my tank with fellow JF member Chillpill109... Had a quarter of a tank left in and still put in about 15 gallons... Feels wrong spending that much on gas.

Anyway, since I had both fill and vent hoses off (and had to cut the inner tube in one of 'em) I'll update if mine hisses or I smell vapors again. It might just have been an awkward angle on the vent hose.

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This is the most metal thing I have ever heard.
Quote:
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I always get people coming over and saying things like "I wish I knew how to do that," etc- but they don't realize- at some point I didn't know how to do it either- I had to figure it out.
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post #11 of 23 Old 04-10-2011, 03:50 AM
shadow57
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I had this same problem. I found the metal vent line that runs along the frame rail had rusted shut. I routed a rubber vent hose and ty raped it to the metal vent lint problem solved.
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post #12 of 23 Old 04-10-2011, 09:14 AM
linusb
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I am a little confused about the vent line because the nipple on the charcoal canister where it connects does not seem to have an opening? it seems as if it's nothing more than a plug for the vent hose?

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post #13 of 23 Old 04-10-2011, 12:23 PM Thread Starter
915kingwrangler
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so then do i have to drop the tank?? no my exhaust is good, actually Im running open headers so my exhaust is no where near the tank, and do you guys know what could happen if i dont fix this quick, i mean the pressure building up in the tank??
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post #14 of 23 Old 04-10-2011, 12:38 PM
moonshinefuel
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Originally Posted by 915kingwrangler View Post
so then do i have to drop the tank?? no my exhaust is good, actually Im running open headers so my exhaust is no where near the tank, and do you guys know what could happen if i dont fix this quick, i mean the pressure building up in the tank??
Worse case scenario, the gas cap has a determined pressure release, and it will release there if it gets too high, or do I have that backwards, it vents air in..
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post #15 of 23 Old 04-10-2011, 12:47 PM
Castr8r
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Pressure build up in the tank is released through the "roll-over" valve(s) into the vent tube that goes to the charcoal cannister. From there it is metered into the intake to be burned. Some pressure is o k in that it is not all released into the intake at once (causes driveability problems). My guess is that the vent line is pinched or rusted shut.

As far as holding the fill nozzle lever, that sounds fairly normal for the YJ. It's not a good idea to walk off and leave the gas pumping in 'cause the nozzle has an annoying tendency to fall out. Some nozzles don't release when they hit the concrete, and lotsa gas on the drive with clueless people- you can figure that out.

I've been throwed out of a carwash- too much mud!

I've done bodywork useing a winch, a tree, a prybar, and a BFH!

Now, my wild oats have turned to prune juice and all-bran...
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