Fuel Tank Venting? - Off-Road Forums & Discussion Groups
Jeep-Short Wheelbase All discussion of short wheelbase Jeeps: CJ, TJ, YJ and JK

Reply
 
LinkBack Thread Tools Display Modes
post #1 of (permalink) Old 07-10-2009, 01:37 AM Thread Starter
I Might Just Know What I'm Talking About
 
JeepDawg's Avatar
 
Join Date: Dec 2006
Location: S. CA
Posts: 1,503
Thanks: 0
Thanked 0 Times in 0 Posts
 
Fuel Tank Venting?

I have a 'slight' issue with my gas tank.

If I fill up all the way I start leaking gas out of the top of my tank. What I think is happening is the vent valve on the top of the tank is getting fuel up to it....the anti-roll over valve shuts.....gas tank builds up pressure and eventually pushes gas around the valve.

If I take the gas cap off there is pressure in the tank....relieving the pressure stops the gas from leaking out....once I get the gas level down a couple of gallons I don't have an issue.....

As some of you may remember I did an SBC swap a couple of years ago....for the most part the vent system is the same....gas tank vent goes to the charcoal canister....though the SBC setup is a lot simpler....only two hoses...one to the tank...the other to a solenoid on the engine....computer does the rest.

Suggestions? Ideas? Thoughts?

AKA DDawg16
84 CJ7, SOA, 5.7LTBI, 4L60E, 35"x12.5, 4.10 gears, F/Det, R/ARB, Full Roll Cage,
D44 Flat top in progress...
Link to my Frame up Restore
JeepDawg is offline  
Sponsored Links
Advertisement
 
post #2 of (permalink) Old 07-10-2009, 03:38 PM
Addict
 
Join Date: Jun 2007
Location: Southern Maryland
Posts: 363
Thanks: 0
Thanked 1 Time in 1 Post
 
Is your solenoid working? That should be pulling some of the pressure off. I had the same problem with my 5.0 swap then I figured out one vacuum hose was out of place, once that was corrected everything was okay. Mine used to build up sooo much pressure the cap would sing at stoplights, very annoying.

BOOGER

IKSS now
Booger is offline  
post #3 of (permalink) Old 07-10-2009, 07:24 PM
I Might Just Know What I'm Talking About
 
Raduckal's Avatar
 
Join Date: Sep 1999
Location: Owensboro, KY
Posts: 1,905
Thanks: 3
Thanked 4 Times in 4 Posts
 
I'd just try a vented gas cap. Don't sic the EPA on me.

"Beer is proof that God loves us and wants us to be happy."

Benjamin Franklin
Raduckal is offline  
Sponsored Links
Advertisement
 
post #4 of (permalink) Old 07-10-2009, 08:44 PM
Veteran
 
TeamRush's Avatar
 
Join Date: Mar 2009
Location: So.West Indiana
Posts: 826
Thanks: 0
Thanked 0 Times in 0 Posts
 
In almost EVERY situation I've had to fix this problme it's been a fill/vent hose rubbed though or split,
OR,
The vent hoses on the top of the tank have given up...

Either way, the ONLY way to fix is to drop the tank and find out what gives!

If you have the PLASTIC tank, there are TWO roll over valves on both sides of the tank and they vent to the emission canister...
These line will harden and crack...

If you have a steel tank, you will probably find the vent line from the sending unit has rusted through and is puking fuel/vapors,
or the line to that vent has given up.

If it were the suction line, you would notice that in a see through fuel filter between the fuel pump and carb....
If the suction line leaks, you will see bubbles in the line,
And you would notice the smell/leak at all times, not just when the tank was full.
----------------------

As for vented gas cap...
STUPID IDEA in a jeep that is going to be driven out of the front yard...

Vent should go through the emissions canister (with roll-over protection)
OR,
Through the roll over valve in the rear of the vehicle....

Unless you just WANT to die in a gasoline fueled fire!

So Many Cats, So Few Recipes...

Last edited by TeamRush; 07-10-2009 at 08:46 PM.
TeamRush is offline  
post #5 of (permalink) Old 07-10-2009, 09:15 PM Thread Starter
I Might Just Know What I'm Talking About
 
JeepDawg's Avatar
 
Join Date: Dec 2006
Location: S. CA
Posts: 1,503
Thanks: 0
Thanked 0 Times in 0 Posts
 
Plastic 20 gal tank....

All the hoses are new....when I did the SBC swap I basically did a frame up restore......all new rubber...all new fuel lines....stainless in fact....

So what I think is happening is that when the tank is totally full, both roll over valves close...hence, no where for the fumes to go.....

Makes me think I need a vent on the filler tube.....

AKA DDawg16
84 CJ7, SOA, 5.7LTBI, 4L60E, 35"x12.5, 4.10 gears, F/Det, R/ARB, Full Roll Cage,
D44 Flat top in progress...
Link to my Frame up Restore
JeepDawg is offline  
post #6 of (permalink) Old 07-11-2009, 04:36 AM
Keyboard Implanted
 
GeeAea's Avatar
 
Join Date: Sep 1999
Location: Pottstown, PA
Posts: 2,076
Thanks: 0
Thanked 1 Time in 1 Post
 
Hmmm...I'm losing something here (conceptually) ..what's stopping it from venting to the charcoal canister ..or is this part of a cycled purge thing?

Gary L. Allan, Sr.
Pottstown, PA

If it ain't broke ..fix it 'til it is
GeeAea is offline  
post #7 of (permalink) Old 07-11-2009, 04:42 AM
Keyboard Implanted
 
GeeAea's Avatar
 
Join Date: Sep 1999
Location: Pottstown, PA
Posts: 2,076
Thanks: 0
Thanked 1 Time in 1 Post
 
If everything is intact and unencumbered (lines working), I'd throw a new cap on. I'm pretty sure that they're still only supposed to sustain so much pressure:vacuum before venting.

Gary L. Allan, Sr.
Pottstown, PA

If it ain't broke ..fix it 'til it is
GeeAea is offline  
post #8 of (permalink) Old 07-11-2009, 09:46 AM
I Might Just Know What I'm Talking About
 
Raduckal's Avatar
 
Join Date: Sep 1999
Location: Owensboro, KY
Posts: 1,905
Thanks: 3
Thanked 4 Times in 4 Posts
 
Wow, I didn't realize what a wild and crazy risk taker I was, driving that 76 CJ-5 with a vented cap all those years. Anybody got one one of those stupid ones that the gas tank was under the seat? Make me a deal and I might save your life. Yes I am stupid and ready to be taken advantage of.

"Beer is proof that God loves us and wants us to be happy."

Benjamin Franklin

Last edited by Raduckal; 07-11-2009 at 10:54 AM.
Raduckal is offline  
post #9 of (permalink) Old 07-11-2009, 10:15 AM Thread Starter
I Might Just Know What I'm Talking About
 
JeepDawg's Avatar
 
Join Date: Dec 2006
Location: S. CA
Posts: 1,503
Thanks: 0
Thanked 0 Times in 0 Posts
 
Quote:
Originally Posted by GeeAea View Post
Hmmm...I'm losing something here (conceptually) ..what's stopping it from venting to the charcoal canister ..or is this part of a cycled purge thing?
I 'think' the fuel is up high enough that it causes the roll over valves to close....which closes the vent.....which causes the pressure to rise....which causes gas to be pushed out....

That or my roll over valves are deffective?......mmmmmmm

AKA DDawg16
84 CJ7, SOA, 5.7LTBI, 4L60E, 35"x12.5, 4.10 gears, F/Det, R/ARB, Full Roll Cage,
D44 Flat top in progress...
Link to my Frame up Restore
JeepDawg is offline  
post #10 of (permalink) Old 07-11-2009, 10:30 AM
Keyboard Implanted
 
GeeAea's Avatar
 
Join Date: Sep 1999
Location: Pottstown, PA
Posts: 2,076
Thanks: 0
Thanked 1 Time in 1 Post
 
Okay ...thanks for the logic train. I needed it.

Gary L. Allan, Sr.
Pottstown, PA

If it ain't broke ..fix it 'til it is
GeeAea is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Off-Road Forums & Discussion Groups forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome