fuel tank not venting - JeepForum.com
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post #1 of 19 Old 06-19-2019, 10:14 AM Thread Starter
ghostrder 04
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fuel tank not venting

si i took a ride out to the mountain's yesterday when i got up to about 5000 ft the jeep started to bog out i removed the gas cap and a lot of pressure came out the jeep ran for about 100 yards and quit again i was able to turn around took the cap off and after a couple of hours and multiple try's the jeep started and ran for about a1000 yards and quit i coasted down to about 3000 ft took the cap off put it back on the jeep started and ran fine all the way home when i got home removed the cap no pressure ,,,,,, anyone have this problem not sure whats goin on 1978 jeep CJ7 304 v8 auto trans all stock

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post #2 of 19 Old 06-19-2019, 11:54 AM
Matt1981CJ7
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I'm inclined to think is was a clog in the roll over check valve that worked it's way free, and not elevation related.

Matt


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post #3 of 19 Old 06-19-2019, 12:46 PM Thread Starter
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ghostrder04

I don't think so because the same thing happened the day before un just about the same place on the road seems like the tank is not venting it is hot weather about 90 degrees or warmer thank you for your suggestion. Also when I opened up the fuel cap along with all the air pressure it also sprayed a little fuel out of the filler

Last edited by ghostrder 04; 06-19-2019 at 01:02 PM. Reason: just to add a little more
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post #4 of 19 Old 06-19-2019, 01:58 PM
keith460
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Where do your vent lines from the fuel tank terminate to?
They should go to a Liquid Check Valve


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post #5 of 19 Old 06-19-2019, 02:56 PM Thread Starter
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yes i see in the manual they should go to a limit fill valve but in looking at it it looks like it goes straight to the charcoal canister
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post #6 of 19 Old 06-19-2019, 03:46 PM
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What have you done to the jeep? Any changes?


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post #7 of 19 Old 06-19-2019, 07:46 PM Thread Starter
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No Changes it was smog checked and passed before i bought it last year it runs fine around the valley i just made the first trip to th mountain's and started having this problem
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post #8 of 19 Old 06-19-2019, 09:29 PM
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If I'm reading your post correctly, you put the gas cap back on each time?

What made you take if off in the first place?

I would have left it off if I suspected a vent issue.


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post #9 of 19 Old 06-20-2019, 07:38 AM
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Quote:
Originally Posted by ghostrder 04 View Post
No Changes it was smog checked and passed before i bought it last year it runs fine around the valley i just made the first trip to th mountain's and started having this problem

Remove the vapor canister and check the filter on the bottom of the can. When they get clogged with road grime, they will cause venting problems.

Beyond that, you are going to have to confirm the vent lines from the tank to LCV, and from RCV to canister, are clear, and that your LCV and RCV are functioning properly.

You should also pick up a venting gas cap. It sounds like you have a non-venting one now.

Matt
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post #10 of 19 Old 06-20-2019, 07:50 AM Thread Starter
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i took it off to relieve the pressure and i put it back on when it started because I had a near full tank of gas and didn't want to drive down through the national forest with the cap off in the heat of the day during fire season spilling gas on the jeep road .
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post #11 of 19 Old 06-20-2019, 08:06 AM Thread Starter
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Thank you Matt I will check that everything you mention is clear yes i do have a non venting gas cap its oem what the book calls for it is a closed system but i will be looking for a vented one today thanks again.
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post #12 of 19 Old 06-20-2019, 08:31 AM
Matt1981CJ7
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The fuel systems on a Cj are not an air-tight system. The tank should never build pressure.

A while back, I was fueling up at a gas station, when a fellow CJ owner pulled up to the pump beside me. When he removed his gas cap, I heard a loud "whoosh" of pressure being released. When I politely mentioned to him that he had a venting problem, he responded irritably and said "that's normal." I just shook my head and continued with my business.

You can lead a horse to water.....

Matt


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post #13 of 19 Old 06-20-2019, 08:54 AM Thread Starter
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Yes you are you are right Matt what i meant was the caps are closed not vented i will try and fix it checking for the hoses or canister being clogged like you suggested but i will also be getting a vented cap for back up before i head out there to check the system
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post #14 of 19 Old 06-20-2019, 03:36 PM
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Quote:
Originally Posted by ghostrder 04 View Post
Yes you are you are right Matt what i meant was the caps are closed not vented i will try and fix it checking for the hoses or canister being clogged like you suggested but i will also be getting a vented cap for back up before i head out there to check the system
What state are you in?

A vented cap is ok for backup, but I wouldn't want to run it like that all the time. Need to find your problem.

If you can, take a pic of the drivers side of your engine compartment and post it.


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post #15 of 19 Old 06-21-2019, 07:58 AM Thread Starter
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I'm in Mendocino county ca. found the problem at some point the nipple on the top of the LCV broke so they put a screw in it causing the tank to vent back into its self thank you for your reply
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