Gas tank swelling and leaking

[OEM1984CJ7]

My gas tank will swell when it gets hot and if I have more than 3/4 tank (20 gal tank) it will come back up through the green vent line into the charcoal cannister and leak out the bottom. I have only the one line on my cannister and have the other 3 plugged. I removed my fuel return line and blew through it and it was clear. I removed the green line from the cannister and blew through it and it was clear. I replaced the fuel cap with a new vented one and it still does it. I took my old fuel cap and drilled a hole in it and it seems to be a little better but still does not vent enough.


Any ideas? I put up with this all last summer of only getting to put 10-12 gallons in it at a time.

Couple of years ago I replaced the sender and cleaned the tank and didn't see anything obstructing anywhere so I am kinda at a loss.

1984 CJ7 AMC 258 i6 / 4.2l

 

[Miles]

Gas tank swelling and leaking could be from your weather in Tennessee . Just a guess .....

 

[tarry99]

My gas tank will swell when it gets hot and if I have more than 3/4 tank (20 gal tank) it will come back up through the green vent line into the charcoal cannister and leak out the bottom. I have only the one line on my cannister and have the other 3 plugged. I removed my fuel return line and blew through it and it was clear. I removed the green line from the cannister and blew through it and it was clear. I replaced the fuel cap with a new vented one and it still does it. I took my old fuel cap and drilled a hole in it and it seems to be a little better but still does not vent enough.


Any ideas? I put up with this all last summer of only getting to put 10-12 gallons in it at a time.

Couple of years ago I replaced the sender and cleaned the tank and didn't see anything obstructing anywhere so I am kinda at a loss.

1984 CJ7 AMC 258 i6 / 4.2l

You should look at a fuel and smog line chart for your application......there is either another vent that is plugged or the fuel is siphoning forward to your cannister.....which could be a check valve in the system that is defective.

 

[Saddle Tramp]

The first thought would be the liquid check valve but it sits fairly high up above the tank. As such it could just be the charcoal canister is saturated. You say you have the line in to the canister from the tank but nothing out to the carb. My bet is when the gas in the tank expands due to temperature rise or is bouncing around as you drive down the road, it pushes vapor into the canister line (still check the liquid check valve) which condenses in the canister and is pushed out from the built up tank pressure as it has nowhere else to go. Actually there should be two lines out, one to the carb and the other to the air horn, both of which pull vapors out of the canister. Reinstalling at least one of these lines might help but I question if the canister can be salvaged once it’s saturated. The only part of the OEM canister that is supposed to be servable is the pad on the bottom. I’ve never had one go south but I don’t think the OEM style part is available however I’ve seen threads about an alternate canister that can be used

 

[OEM1984CJ7]

It even does it with the jeep sitting parked and not running. I noticed it the first time when I went to get in it at work and there was gas dripping from the charcoal cannister, went around back and loosened the gas cap and pooof --pressure.

 

[tarry99]

It even does it with the jeep sitting parked and not running. I noticed it the first time when I went to get in it at work and there was gas dripping from the charcoal cannister, went around back and loosened the gas cap and pooof --pressure.

Again, Look at a smog line chart..........there is a vent or check valve that is not working.

 

[OEM1984CJ7]

After looking at it further when I got home today I do not have any of the rollover valve or check valve stuff in my rear wheel well housing. I found a diagram of this at one time on here that Keith posted that was very nice and showed everything but cannot find it now.

 

[Petescj]

I never really looked into this stuff but its probably on the carcass of my 85. Shoot me a pic or 2 of everything you need.

 

[Saddle Tramp]

Try this:

 

[wm69]

I thought the rollover/check valve was in the tank on a 20 gal unit...?

 

[OEM1984CJ7]

It wasnt in there when I pulled it last year and replaced the sender. I don't know what the PO did before.

Petecj, I need the two parts in the previous diagram labled Rollover check valve and Liquid check valve. PM if you have them

thanks.

 

[Petescj]

I'll give it a look when I come home from work tomorrow.