Too much pressure in fuel tank? Leak at filler neck gasket. (1 Viewer)

[Tighe]

Hi all,

I had a bit of an unsettling experience this morning- I parked my (new to me) FJ60 on a hill, nose up, last night and this morning discovered a pretty steady fuel leak originating from the gasket just behind the fill cap and before the filler neck. The two screws on either side of the fill cap are tight.

I rolled the truck down the hill to flat/level ground and opened the fill cap, and a big gush of gasoline came out. It subsided, and I put the fill cap back on.

That was a few hours ago- I just went outside to check the pressure by taking the fill cap off, and again a substantial amount of gasoline came gushing out. I have not started it this whole time, and it has been sitting in the sun.

The gasket at the filler neck may very well need replaced, but there seems to be something else preventing the fuel pressure from escaping. I've been driving it steadily for the last few weeks with no apparent issues, and I just filled it up with gas last night, so the tank's full.

I've been reviewing related threads on this forum, and will continue to do so, but I wanted to post this in case it anyone's had the same experience and can chime in.

Thanks for the help.

 

[Dynosoar]

First place to check is your Charcoal Canister. your tank is not venting properly. Gasoline can boil at temps as low as 90 F. Some people have had success switching the lines on their canister. Search for related posts/threads.

Dyno

 

[Tighe]

Thanks Dyno. The CC's on my list of things to check- I'll put it to the top. Off to buy a fire extinguisher first!

 

[Joe_E]

Check with Toyota if your fuel tank recall has been done.
Mine did that before they changed the tank many moons ago.

 

[brian]

Check with Toyota if your fuel tank recall has been done.
Mine did that before they changed the tank many moons ago.

thought i read something a few months ago about that recall being closed.

 

[Slow Left]

Also might want to take a quick peek in behind that PS panel in the rear cargo area (where the gas tank vent separator/hoses are) and make sure the gas hasn't pooled down in the rear quarter panel area.

 

[Tighe]

Thanks for the replies. I'll check with Toyota tomorrow about the recall and will report back.

Slow- gas definitely would have pooled under the filler neck but there must have been a way through to the outside- I first noticed the leak from the exterior of the truck- there was a small pool of gas under the PS of the rear bumper.

I have since backed the truck up so the rear was higher than the front, and, with the cooler temps here at night in Santa Fe, NM, there seemed to be no pressure buildup. I just checked the gas cap after sitting (sun's been down for several hours now) for a few hours, and there's no drip from the gasket, and no gas smell inside the cabin. A relief.

I will investigate the charcoal canister and the lines to it over the next week. I have noticed that every time I go to fill up there is a strong woosh of gas vapors that come out. Only today did any liquid gas actually come out- presumably because of the combination of a full tank, parking on a slope, and sitting heating up under the sun all day. Glad I caught it, thanks to all for the help.



In other news I figured out today that I could use a bump stop from the rear bench seat bottom as a bump stop for the hood. The stops for the hood were cracked and useless, and I had some extra rear seat parts laying around. Perfect fit.

 

[Bear Lake Cruiser]

I often hear the fuel bubbling and a cooking in the tank and fuel separator area but have yet to have a pressured overflow. and vapor. And it does this regardless of temperature

 

[Joe_E]

Also might want to take a quick peek in behind that PS panel in the rear cargo area (where the gas tank vent separator/hoses are) and make sure the gas hasn't pooled down in the rear quarter panel area.

Yes.
That's where some of the gas will collect. It thens melts out any of the asphalt coating in the corner panel and causes the drain slot at the bottom to clog.
Next thing you here will be water sloshing around in the corner panel because of the clogged drain slots.
It's the natural turn of events.

 

[Output Shaft]

The usual culprit for an improperly venting '60 gas tank is the charcoal canister's internal check valve.. it gets gummed up and sticks. You can clean it by spraying a little Chemtool down the IN (Tank) tube on the canister, and blowing low pressure (40 psi) air down the tubes as described in the manual. That will usually fix it up and let the tank breathe properly.. or just swap the purge and vent hoses on the canister to bypass that pesky check valve. Also, don't fill the tank full to the brim.

 

[Tighe]

Thanks! I picked up an extra charcoal canister from a jy 60 that I was going to try. Haven't gotten to it yet but I will report back. I really appreciate the advice.

 

[Spook50]

The usual culprit for an improperly venting '60 gas tank is the charcoal canister's internal check valve.. it gets gummed up and sticks. You can clean it by spraying a little Chemtool down the IN (Tank) tube on the canister, and blowing low pressure (40 psi) air down the tubes as described in the manual. That will usually fix it up and let the tank breathe properly.. or just swap the purge and vent hoses on the canister to bypass that pesky check valve. Also, don't fill the tank full to the brim.

View attachment 933429

Hey @OSS, is this the same procedure for the 62 charcoal canister? I know I've asked this question before, but I can't for the life of me find the thread where I asked about the canister.

 

[OSS]

I'm not familiar with the 62 charcoal canister... but they all fail the same way—internal check valve gets gummed up and doesn't work properly. Unfortunately the check valve is built into the canister when it's getting formed and isn't accessible without wrecking the canister

 

[fjbj40]

80 series experience the same thing, here is a cure, I did it and it ended my problem of over pressuring the tank. I put an end to my Charcoal Canister problems for good!
I did not figure out this fix, a long time contributor did!

 

[Spook50]

I'm not familiar with the 62 charcoal canister... but they all fail the same way—internal check valve gets gummed up and doesn't work properly. Unfortunately the check valve is built into the canister when it's getting formed and isn't accessible without wrecking the canister

I finally found my FSM this afternoon, so I got it all figured out. Just gotta pull the canister and see if I can get it functioning right, then make sure the VSV is working as it should. New fuel tank cap should get here on Thursday so hopefully all will be well with the world once it's all done

 

[joecat66]

my tank was so pressurized it blasted me head to toe w/gas when i removed the cap...it was the charcoal canister. I also had gas inside the rear fender by the filler neck. Unlike some old cars i don't believe it can be opened up and serviced w/fish tank charcoal...you can switch the hoses around on the top and essentially bypass it to solve the problem