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Unread 11-21-2005, 10:24 PM   #1
Wolf359
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Fuel Leaking from Charcoal Canister

I recently replaced my canister because it had broken hose nipples and I needed to get the CJ smogged. It passed with no problems. Yesterday while I was out in the desert, I notice fuel dripping from the bottom of the canister. I've double checked the hose connections, especially the one going to the fuel tank and it is all hooked up correctly.

I suspect the rollover check valve is bad. Is there a way to check it without rolling over the Jeep?

Also.. I'm using a canister for a 258 motor... My CJ has a '92 4.0L. The 258 canister has 4 nipples on top and the one for the 4.0L has only two. Should I just get a canister made for the 4.0L?

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Unread 11-21-2005, 10:36 PM   #2
only in a jeep cj
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The only time I ever had fuel leaking out of the can was after my Jeep came back from the shop (I was rearended and they dropped the tank to replace the rearframercross member) AND after I filled up the tank all the way....I knew they f'ed something up because 14 years of driving and working on this Jeep, I knew it inside and out. The lines are hard to trace through the frame and down the rails, etc. I thought they were right at first, but found they mixed up the vent and return line. So I had gas going from the filter into the rollover valves and the lower return tube (part of the sending unit) was sending fuel down it via tank pressure build up. It poured out of the char can. This may or may not help, but that is what happened to me.
I'm doing a 1994 4.0 swap now and will be using a YJ can....I figure play it safe. The CJ version has a carb vent that the YJ didn't......
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1975 CJ-6 304 T15 Dana20 30/44 3.73
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Unread 11-22-2005, 12:29 AM   #3
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Thanks ED... I think I'm going to go with a 4.0L canister as well. It's weird because I haven't seen this problem until yesterday on a trail which wasn't even that bumpy. I'll go through the system again and trace out the hoses.


Pete
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Unread 11-22-2005, 03:10 AM   #4
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Mine used to do that when the tank would build up pressure and drip out of the canister. It sucked something back up into the line and plugged it up. I never unclogged the line when I put the new frame under it about 5 years and still don't have any problems with it. You might just clamp the line off, after your gas cap gets old it will vent it.
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Unread 11-22-2005, 10:41 PM   #5
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I was going to put another valve inline but I suppose pinching it off will stop the fuel from getting into the canister for sure... Thanks.

I'm probably still going to get a canister for a 4.0L to replace the original one for the 258. I wonder if a new gas cap will help. The one that's on there is a locking type and it's hard to take off sometimes...
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Unread 11-23-2005, 04:57 PM   #6
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A good gas cap is what caused my problems the tank would build up pressure . The pressure would leak out the gas cap and forced gas out the canister.
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Unread 11-24-2005, 12:00 AM   #7
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Yeah, but even under tank pressure, liquid gas should not reach the canister due to the check valves. I believe its a plastic ball or a rubber diaphram type of flap that that closes if liquid pushes on it.....plus these valves are at the highest part of the tank. Gas fumes or air/gas pressure will not close them though. The other two lines are either sucking up gas or returning it so if the vent line is clogged shut, the cap will then vent as it has a slight pressure bypass built in. Either way, if gas is comming out of the evap can, something is wrong.
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1975 CJ-6 304 T15 Dana20 30/44 3.73
1983 CJ-8 258 T5 300 30/44 3.31 Looking for full or half hardtop buy or trade
1986 CJ-7 Laredo 4.6 stroker T5 300 30/44 3.31
1986 TJ-7 Trail Jeep project in the works
2003 Inca Gold TJ Rubicon
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Unread 11-24-2005, 06:53 PM   #8
Scrambler Jimmy
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If your CJ has the 15 gal tank, then it'll have an external liquid check valve. That's what prevents the gas from reaching the charcoal canister. IIRC, the 20 gal tanks had a built-in liquid check valve.

The top to the liquid check valve snaps on like a 5-gal bucket lid. If you're real careful, you can unbolt the valve, pop off the lid, and clean it out if there's something keeping the float stuck in the open position. It has a needle and seat system similar to a carburator. It should make sense once you have it out and opened up.

EDIT - I should have added... I just put one on my Scrambler after the exhaust pipe got bent up under the body when wheelin' some big rocks at PAP. The hot exhaust collecting in the corner of the tub melted/dissolved the LCV. So I picked up another off a parts vehicle and opened it up and cleaned it out as a just-in-case.

Last edited by Scrambler Jimmy; 11-24-2005 at 06:57 PM.. Reason: Added add'l info
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Unread 11-24-2005, 08:19 PM   #9
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Do you have to run the charcoal canister? Why is it needed?
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Unread 11-24-2005, 10:38 PM   #10
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I live in San Diego so the canister is required because of California's emissions laws.
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