Excessive fuel tank pressure

[Atoyot1031]

Got to GJ. With the 30k in the fan ckutch, the temp on my RT modded gauge never got over half.

The surface temp on my gas tank (nearly empty) was ~125F. My LR was 106F. For comparison the asphault was 128F. All measued by my IR thermometer.

There was a gas smell from the filler neck. When I went to gas up, with the cap cracked open, it ook ~30 seconds to vent, but as previously mentioned the tank was almost empty.

 

[Ebag333]

I'd say that's normal. 30 second venting time for me is fairly common, especially if low or empty.

 

[MaddBaggins]

My question exactly - is this a new issue just coming to light, or is is something that has been discussed before when the vehicles were only, say, 11 years old... Does not seem like anyone was aware of issue prior.

I think it has a lot to do with the newer gas formulations. They are adding more ethanol and ethanol lowers the boiling point.
I've been smelling gas from lots of other vehicles besides our older cruisers.

 

[SUMMIT CRUISERS]

I think it has a lot to do with the newer gas formulations. They are adding more ethanol and ethanol lowers the boiling point.
I've been smelling gas from lots of other vehicles besides our older cruisers.

I think you're right on it. As gasoline/gasohol is heated the lighter ends vaporize off. When I experienced the problem, even my wife and kids commented on the strong alcohol/ethanol smell not the smell of gasoline. In Oklahoma 100% gasoline is widely available and is the only fuel I purchase so we know what real gasoline smells like. I only have these gas tank pressure issues while 4 wheeling in high altitudes and while using E-10. One more comment, I have never been able to find 100% gasoline in these higher altitude areas to test this theory.

 

[Ebag333]

So over the last few weeks we've had some pretty strange weather around here. Not so good for your garden, or even picking what to wear in the morning, but great for testing fuel line temps.

We've gone from 50* temps to 107*. One morning was over 90* and in the afternoon had hail so large I was worried I was going to break my windshield!

Anyway, through all of that I can absolutely say that the number one factor in fuel temps would be ambient temp. I don't think there was much doubt about that, but I think many of you would be surprised at how hot that ambient temp gets. I have a temp gauge in my engine bay, and the fuel tank would regularly get as hot as my engine bay would just by sitting outside in the sun (regularly 110*-125* F). What ever my engine bay temps were, the fuel temps were very close to that. On a couple of the hottest days, temps were pushing 150*. And that was before I even turned the key!

I know that there have been studies that have shown that the inside of vehicles can push 200* in the hottest climates. That's far above the boiling point for gas.

The second biggest factor is load and time. If you're running with a low load, then temps could very likely drop (assuming you started with a high ambient). If you're running a high load (stop and go traffic, up hills, heavily loaded, etc), especially over a lengthy period of time, then fuel temps can climb quite significantly.

I haven't had the chance to go wheeling yet, but considering that your temps are going to be significantly higher than just driving around, I have no doubt that fuel temps will be significantly higher as well.

 

[ajax1]

i have an a 94 80 series and have never had a fuel pressure prob yet, i live at 7800 ft in gunnison colorado and regularly drive up to 13000 ft, and i run ethanol blend of gas i think it is up to 10 percent, it also doesnt get hot here>my truck has also been at high altitude its whole life

 

[1972FJ55]

I think it has a lot to do with the newer gas formulations. They are adding more ethanol and ethanol lowers the boiling point.
I've been smelling gas from lots of other vehicles besides our older cruisers.

I can confirm that (at least in my case) fuel in the tank is boiling. I drove to Bisbee (5300') last weekend, temps in the mid to high 90's. While unloading the tool, dogs and misc crap, the vapor smell was pretty strong. I removed the gas cap (took about 30 seconds to release the pressure) and I could distinctly hear the fuel in the tank boiling. I waited a few minutes to see if it would stop, but it continued. I replaced the cap for just a few seconds, and when I removed it, pressure had already built up in the tank. So now the question is what, if anything to do about it. I haven't suffered any driveability problems, and mileage is still in "normal" range, so just accept it?

 

[landtank]

What are you guys running for fuel? Maybe there is a better brand than others for this problem.

 

[nocrawl]

that's your cruisers way of asking for a cold beer

 

[The Moe]

So, do you guys think that this venting may effect the performence... If so, would insolating the tank help? I do have the same effect in my 97 40th she burbs for a min or so when the fuel is low... I have a 06 4Runner that never done that...

 

[SUMMIT CRUISERS]

What are you guys running for fuel? Maybe there is a better brand than others for this problem.

Rick, not to get into a fuel debate here, but brands don't really matter. How the fuel is distributed, delivered and the station tank and equipment condition really does matter. I ran Conoco 91 purchased in Durango and Silverton and had the problem. I never run anything but 100% 87 in Oklahoma but up there with the strain on the motor from climbing I chose the 91 with ethanol. How much ethanol was in it? I couldn't tell you. That's the key, ethanol, is it in the fuel? and how much?
Steve

 

[SUMMIT CRUISERS]

So, do you guys think that this venting may effect the performence... If so, would insolating the tank help? I do have the same effect in my 97 40th she burbs for a min or so when the fuel is low... I have a 06 4Runner that never done that...

Probably not, just smells really bad and produces passenger headaches. I'm thinking the problem comes from the fuel rail being directly above the exhaust manifold (3FE Inline 6, Not sure about the fuel rail on the 97 1FZ or the 06 4Runner)
When this happened on my 92, I vented the tank by taking off the cap slowly. After the boiling stopped, sometime later, I tried to start it. It acted like I just changed the fuel filter, no fuel pressure and it took a while to get it started. When I left the fuel cap on the truck, it started right up. Conclusion...Fuel line is puking/boiling back into the tank when the pressure is relieved (cap removed). Is the entire tank boiling, highly unlikely, mine was 3/4 to full when it happened.

 

[MaddBaggins]

What are you guys running for fuel? Maybe there is a better brand than others for this problem.

I've tried various brands, nothing helps.

 

[MaddBaggins]

i have an a 94 80 series and have never had a fuel pressure prob yet, i live at 7800 ft in gunnison colorado and regularly drive up to 13000 ft, and i run ethanol blend of gas i think it is up to 10 percent, it also doesnt get hot here>my truck has also been at high altitude its whole life

I can confirm that (at least in my case) fuel in the tank is boiling. I drove to Bisbee (5300') last weekend, temps in the mid to high 90's. While unloading the tool, dogs and misc crap, the vapor smell was pretty strong. I removed the gas cap (took about 30 seconds to release the pressure) and I could distinctly hear the fuel in the tank boiling. I waited a few minutes to see if it would stop, but it continued. I replaced the cap for just a few seconds, and when I removed it, pressure had already built up in the tank. So now the question is what, if anything to do about it. I haven't suffered any driveability problems, and mileage is still in "normal" range, so just accept it?

I now understand that it isn't a pressure issue. The gas cap is rated at 4psi IIRC, so pressure is not an issue. The gas is boiling and the evap system can't keep up with the excess vapor. When you open the tank it allows the gas to boil rapidly.

just leave the gas cap on and let it calm down on it's own.

 

[MaddBaggins]

Rick, not to get into a fuel debate here, but brands don't really matter. How the fuel is distributed, delivered and the station tank and equipment condition really does matter. I ran Conoco 91 purchased in Durango and Silverton and had the problem. I never run anything but 100% 87 in Oklahoma but up there with the strain on the motor from climbing I chose the 91 with ethanol. How much ethanol was in it? I couldn't tell you. That's the key, ethanol, is it in the fuel? and how much?
Steve

10% ethanol in Tucson.

 

[Jeeper]

Just posted a new thread, and thought a cross-post would be useful for those following this thread:

https://forum.ih8mud.com/80-series-tech/412261-charcoal-canister-great-option.html#post5860891

Basically, I found an almost drop-in replacement canister for $36 that has solved completely solved my problems after 6 fillups. Details in the link above.

Hope this helps,

 

[Ebag333]

Awesome find! I'm going to have to pick up one of these I think.

Interestingly enough, I recently replaced my gas cap. I was parked on a driveway that was sloped after filling up, came outside to smell fuel and see it dripping from my rig!

Appears that the seal on the gas cap failed. That would explain why I was having problems, the system never got up to 3 PSI which would allow the fuel to start evaporating when it was hot out. So far so good, fuel smells are gone, no extremely high pressure like before.

 

[Marc311]

When you all speak of "excessive pressure", are you talking about positive pressure? I always have a vacuum when I open the tank to fill up. Not sure if it is a cap issue, canister issue, or no issue.

I also know from my old HS chemistry class, that liquids boil quicker with less pressure. It seems these altitude problems would be aggravated by a vacuum, not from excessive positive pressure.

 

[treerootCO]

Mine spits fuel out the filler neck and you can hear the fuel boiling in the tank. If I want to fill up, the pressure is enough that it kicks off the pump. It boils for literally five minutes when I take the cap off. This is at 9953ft in elevation for reference.

 

[BirfMark]

I drove from 5000' to 8400' on a 43 mile trip Friday night while towing my 3,000lb popup. My temp gauge was reading 215°+, and my transmission gauge was running near the 195° mark. When we finally got to camp & shut the truck off, I noticed a pretty strong gas smell up around the hood.

I assume my charcoal canister/evap system was overloaded & venting, though I did not hear my fuel boiling in the tank. Anytime I crack the fuel cap at the gas station (whether after driving around town, or across the state), there's always pressure in the tank - it noticeably 'whooshes' a decent volume of air out, oftentimes for 10 seconds or more. If I put my hand over the filler area, I can actually feel the fumes coming out.

Is it possible that the evap system can siphon out of the tank, even after the engine is shut off? The reason I ask is because this trip on Friday night afforded me my worst ever fuel mileage - right at 11mpg. The motor is on a fresh tune-up with new plugs, wires, cap & rotor, air filter, & both fuel filters. I know these trucks don't get good mileage, but 11mpg just didn't seem right for that trip.