Gas Tank Vent Issues - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 06-18-2003, 10:01 PM Thread Starter
 
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Gas Tank Vent Issues

I have my 83 CJ7 with a plastic gas tank.. I bought a new gas cap since I have been having problems with pressure building up in my tank. Well it actually came to the point where when I moved my gas return line to get at a bolt, it developed a small leak, and actually was forcing gas back through the return from the tank...

Anyway, my question is, does the tank vent through the gas cap, or does it have another method for this?

Would this problem contribute to me only getting 8.5 mpg with the rebuilt 360?

Thanks..

Justin.
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post #2 of (permalink) Old 06-18-2003, 10:50 PM
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Re: Gas Tank Vent Issues

1. The 83 has a Roll-over valve on the supply line,
2. Two top mounted spring loaded emission valves on the top of the tank.
3. One return line in the sender assembly.
4. The cap should be vented.
5. If you've moved the gas line and it leaked...
5. You'd best replace the line...
6. That "flexi" line is nasty to find a leak in...
7. It could alos be the flexible line to the vents and senders.
8. I CAN NOT STRESS ENOUGH FIND THAT LEAK.
9. This has now become a serious safety issue.





Last edited by LEVE; 03-24-2009 at 07:44 PM.
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post #3 of (permalink) Old 06-18-2003, 11:07 PM
 
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Re: Gas Tank Vent Issues

Do a search on gas tank vent and you should find all the info. you'll need.

Here is a diagram that might help also.


Lee
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post #4 of (permalink) Old 06-18-2003, 11:13 PM Thread Starter
 
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Re: Gas Tank Vent Issues

Actually the leak developed where the rubber hose, joins with the steel line between it and the filter.. I have one of the cheap clamps, and not an actual hose clamp.. Anyway, I took off the cheap clamp, and pulled the hose off, and that's when the gas really started flowing from the tank, back up the return line.. I now have a good hose clamp on, and no more leak..

As for the build up of pressure, I have a vented gas cap, but still build up a lot of pressure in the tank.. When I remove the filler cap, I have to remove it slowly to let the pressure release..

Any more thoughts?

Thanks..

EDIT: Didn't see the next post before I replied.. I don't think my tank is set up like that, but I will have another look tommorow.. Thanks for the breakdown..

Justin..
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post #5 of (permalink) Old 06-18-2003, 11:37 PM
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Re: Gas Tank Vent Issues

1. CJ7inBama, that's not an '83 stock CJ7 Poly tank...
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post #6 of (permalink) Old 06-18-2003, 11:41 PM
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Re: Gas Tank Vent Issues

1. There is some vacuum built up in the tank,
2. That's a given.
3. A mechanical fuel pump can't collapse the tank,
4. Due to suction,
5. If you've got the leak cured,
6. I'd not worry about the vacuum.
7. Pressure will neutralize over time.
8. That vented cap doesn't have a hole in it...
9. It's designed to keep vapors in.
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post #7 of (permalink) Old 06-19-2003, 12:13 AM Thread Starter
 
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Re: Gas Tank Vent Issues

I don't think that is it vacume building up in the tank.. It is actually pressure.. This pressure wants to force the gas out of the tank. when I disconnected the line when it was leaking it was coming out of the *return* line FROM the tank.. Now I know there will be some ags in the line, but I would say that after disconecting the line, it probobly purged all the gas sitting in the line from the tank back..

There was one time then I took the cap off too fast and it actually forced gas up the filler tube, and out.. Now I haven't had that happen since I replaced the cap, but I have also been careful taking the cap off, and slowly letting the pressure out...

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post #8 of (permalink) Old 06-19-2003, 12:16 AM
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Re: Gas Tank Vent Issues

1. OK, now I'm getting a better picture.
2. I wonder if that Evaporation Canister is bad?
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post #9 of (permalink) Old 06-19-2003, 12:40 AM Thread Starter
 
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Re: Gas Tank Vent Issues

No such thing anymore.. All emissions *stuff* is gone.. Except for the EGR valve..
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post #10 of (permalink) Old 06-19-2003, 09:06 AM
 
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Re: Gas Tank Vent Issues

Woops.... Sorry for spreading disinformation. I saw "Gas Tank" and "Vent" in the subject line and jumped the gun. Thanks for correcting me.
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