Fuel leak out of gas cap. (FJ62)

[FJlynch]

So there I was, enjoying my coffee on a nice Spring day. I decided to open some windows and let the breeze come in only to be surprised with the strong smell of gasoline.

I look outside and there it is, a giant puddle underneath the left rear panel of my 62. I expected the worst.

I walked outside to check out what was going on and wash the gasoline away. Gas was literally seeping out of the gas cap. It did this for awhile before it finally stopped.

I filled up my gas tank for the first time yesterday. (Bought the truck two weeks ago) I suspect I overfilled it, I've read a few other reports of this happening.

My gas gauge must be off or it's extremely generous. I was close to the E line and only put in a little over 16 gallons, meaning I had almost 8 gallons of gas left in the tank. This is what caused me to try putting in more fuel.

Anyways, I'm wondering if there is a chance something else could have caused this. I made sure there were no other leaks from the gas tank, it was only leaking from the gas cap. No issues until today, the day after I filled up. Guess I will stop short a couple gallons from full from now on because I don't like watching money pour out on the ground.

 

[FJlynch]

Also I should mention I will definitely be getting an OEM gas cap. I don't think the one on it now is original and it's probably really old.

 

[SteveH]

Check the rubber gaskets in your existing cap to see if they are rotted. Not overfilling is a good idea, but at the rate FJ62s suck down gas, I rarely have a 'buildup' of gas by the time I drive home 10 miles from the gas station.

 

[Output Shaft]

Only way it could gush out like that is if you filled it all the way up.

Gasoline stored in underground tanks is cooler than the afternoon air. The gas in your tank probably heated up and expanded.

An OEM cap won't let fuel flow out of the filler neck when tightened up. Only lets air IN.

 

[FJlynch]

Check the rubber gaskets in your existing cap to see if they are rotted. Not overfilling is a good idea, but at the rate FJ62s suck down gas, I rarely have a 'buildup' of gas by the time I drive home 10 miles from the gas station.

They aren't rotted but loose, so I'm sure that didn't help the issue. Gas station is only 4 miles away and it's all down hill on the way home.

Thanks for your input.

 

[FJlynch]

Only way it could gush out like that is if you filled it all the way up.

Gasoline stored in underground tanks is cooler than the afternoon air. The gas in your tank probably heated up and expanded.

An OEM cap won't let fuel flow out of the filler neck when tightened up. Only lets air IN.

That's what I suspected. It was a hotter than usual day here in the mountains. Ordering the gas cap tonight. Thanks

 

[LAMBCRUSHER]

remove lines from charcoal canister and vapor seperator and blow clear. Test VCV on Charcoal Canister. Test Charcoal Canister. these lines/vcv/canister serve as the vent for the tank to prevent things like this. If it is spewing gas, it needs to have the vent path checked...

 

[FJlynch]

remove lines from charcoal canister and vapor seperator and blow clear. Test VCV on Charcoal Canister. Test Charcoal Canister. these lines/vcv/canister serve as the vent for the tank to prevent things like this. If it is spewing gas, it needs to have the vent path checked...

It wasn't "spewing gas", just seeping out. The truck happened to be leaning to the left as my driveway is slanted, which didn't help my case. The combination of overfilling and bad gas cap is probably what caused this, but I will check the charcoal canister and vapor separator as I don't think they have ever been looked at. Thanks.

 

[jgschmitt99]

Having the same issue. If I have an OEM gas cap and it doesn't spew out when the pressure builds up, isn't that even more dangerous? I don't want something to burst. Thoughts?

 

[micruz60]

Having the same issue. If I have an OEM gas cap and it doesn't spew out when the pressure builds up, isn't that even more dangerous? I don't want something to burst. Thoughts?

Overpressure is handled by the Charcoal canister, and if not functional it could rupture your tank.
More here:

1987 FJ60 charcoal canister replacement question

I know there are other threads, but I’m have a question that I haven’t found the answer to yet. On the AC Delco replacement canister, there are three ports on top. The original has three on top and one on the bottom. This leaves me with one extra port. I have figured out the intake and purge...

forum.ih8mud.com

Similar for FJ62

 

[micruz60]

Having the same issue. If I have an OEM gas cap and it doesn't spew out when the pressure builds up, isn't that even more dangerous? I don't want something to burst. Thoughts?

Also:

Fuel tank over pressurizing

I think this is related to the fuel smell that I had noticed a short while back (which I hadn't noticed since then, so that's kind of odd), but the other day I saw sings of fuel getting past my filler cap and out underneath the fuel door on my 62. I checked the cap and it still has a good gasket...

forum.ih8mud.com

 

[OSS]

A properly functioning new OEM gas cap won’t release pressure in the tank. It will allow air to get sucked in though through its check valve

 

[Roonie]

It is your charcoal canister. All of them clog all the time eventually. Mine is still oem but I just switched the tubes on top and it stopped the gas leaking out problem. The gas leaking out is when it is full and warm out it expands. It has been happening to my truck for almost 25 years. Some people will drill a small hole in their gas cap but I would worry about water intrusion. Yes I have replaced the gas cap many times and made it air tight but you risk rupturing the gas tank or seals. When you release the cap a huge woosh of air is heard.

 

[Paullus]

If after opening the cap there is no "spew" then I think the charcoal canister is doing its job.

I "rebuilt" my charcoal canister. It has an upper and lower filter disc with charcoal media in between. I changed out the old charcoal with new. The old didn't look too bad but reaked of gasoline. I no longer get any pressure/vacuum noise when removing the gas cap (I should point out I'm not really driving my FJ60 and haven't had more than 4 gallons in the gas tank). I say "rebuilt" cause I cut the thing open just above the upper filter disc.

The layout of the fuel tank is such that once it is over 3/4 full there will be fuel sloshing into the big horizontal hose (looks like a radiator hose). There is a backflow flap but it might be rusted open or stuck open due to aftermarket fuel tank resealer. If the fuel level/sender is working, I wouldn't fill it to the max in the summer.