Gas tank building excessive pressure & fuel smell. Dangerous for sure! Why does this happen?

[econcepts]

DANGEROUS GAS PRESSURE BUILD UP IN GAS TANK!
Why?
What's going on?
How can we fix this?

Edited 7/4/20: What I found in the first case of "fuel boiling" I worked on, was engine overheating or running hot.
Edited 7/5/20: Anyone having and OBDII reader that can watch engine coolant temp and report back here, would be very valuable data. Whether having these issue or not. Other data points in order I feel of most value; Long term Fuel trims (LT FT), Engine RPM, MPH, CAT Temps.

So I'm working on a 99LC w/210K miles. A nice clean rig that's been garage kept and well maintained, or so it seems by history and at first glance. Owner (Gavin) was referred to me. He's been having the issue for ~4 years and it's getting worst. He had a number of local shop work on it, and a few tried to solve this issue. Charcoal canister was replace with a used one from salvage yard.

Gavin reported to me his fuel tank fill cap, when removed, will have fumes blowing out continuously under pressure as cap removed. The sound and smell of gas vapor will go on for an extended period of time, not just the normal short hiss. Fuel smell is filling cabin at times, while driving. At times gasoline smell comes from under the hood. This is worst on hot days, especially when driving in mountains of Colorado. But will also happen just driving around Denver, just to lesser extent and less often.

I've read about fuel tank pressure issues in mud for years now. In some cases the off road guys here in CO, have had fuel coming out gas fill cap area. Reports of cap flying 20 feet through the air as it's removed. Some pictures around, where one can see the fumes coming for fuel fill area. One reported (pictures in mud) of a fire at gas tank.

Seems the off road group have found a few things that help here:
1) Only fill fuel tank 3/4 full.
2) Not using gas with ethanol.
3) Installing heat shield between exhaust and gas lines.

This is first one I've had to work on with this issue. I did not witness issues, so only going on what Gavin explained to me.

I've had my doubts what is cause this being heat from normal exhaust temperatures. Whereas I'm not saying 1), 2) and 3) aren't a benefit. But why isn't every land cruiser having these issues. Why aren't more pictures of fuel running down body at gas cap. Why has this not been addressed by Toyota. If this is a design fault, they'd have a liability if not addressed by now, or did Toyota address? The issue could be deadly. Fumes of gasoline are deadly alone, and highly flammable.

So whats your thoughts on cause or causes?
What has worked?
Is one issue or many that need addressing?
Thoughts?

I'll post some threads on issue here:

100 Caught fire & gas tank venting concerns

forum.ih8mud.com

Had something similar happen in my 60 once at high altitude and it turned out to be oxygenated gas. Something they were doing in CA at the time. eh, probably unrelated.

 

[OwnerCS]

Is there a difference in number of cases between 98-02 vs. 03-07 models with the evap canister location moving from engine compartment to under vehicle?

 

[JohnnyMackerel]

03 LX here

 

[CCFDCAL]

The biggest change for me, and I"m not going to say it's "solved" was the pre-cat O2s (I did this along with spark plugs). I don't have any measurements, but I'm assuming my exhaust gas temps went down.

Sure it's been cold outside, but we are using the crappiest blend of Ethanol here in Utah (85 octane even) and I live above 5k feet, have gone to moab and idled a ton, and hardly get any venting out of the tank at a fillup. I'm not talking boiling now, hardly any venting. And when I do get venting, it's just a quick short hiss (like any other car).

So far I've done: VSV, cannister, gas cap, spark plugs, and pre-cat O2s. I bought stuff for a heat shield, but when I went under there my cat already had a factory shield that was bent to deflect away from the fuel lines so I wasn't sure what I was supposed to do with my homemade thing.

Only summer will tell. I've had dangerous levels of boiling and fumes with both non-ethanol and ethanol fuel at high elevation and low elevation. The only common denominator seems to be heat (the boiling almost always happens when idling or crawling in 4-low for extended periods). This last trip to Moab the temperature was 60F, hardly the 90F which caused me to evacuate the vehicle at 4500 feet using regular gas or a mild ethanol blend two years ago, but the tank didn't even hiss when I went to fill up after the trail. That was a small victory.

This is happening to me to with the same conditions. I never have an issue until the hot temps in Las Vegas come around. I actually plan my fuel ups so I am almost empty when I travel to Utah. If I have too much fuel in the tank and its boiling I am unable to fill up until the temp lowers. I can continue on my journey with fresh cool fuel. Otherwise I'm stuck for an hour or so. I have changed the gas cap, charcoal canister, and plugs as well. I've also applied heat shield. None of that has worked. I just ordered my pre cat sensors. I'm hoping that will solve the problem. If not I may have to get rid of the old girl. I'm over dealing with this problem. I'm optimistic that this will work though.

 

[CCFDCAL]

Interesting. If this works as a solution, then it means the temperature of the return fuel plays a significant role in causing the boiling and excessive pressures in the fuel tank. The boiling over in my LC100 was solved by wrapping the fuel return lines with reflective heat wrap where the lines pass close to the exhaust -- also lowering the temperature of returning fuel. I'm not saying its the only cause, but trying to lower the temperature of the returning fuel seems like an important solution as long as other maintenance is up to date.

I agree about the returning fuel temps, but why the change in temps? Why does the temp of the returning fuel increase over the life of the vehicle? Mine started at about 100k. I bought it with 88k.

 

[JohnnyMackerel]

This is happening to me to with the same conditions. I never have an issue until the hot temps in Las Vegas come around. I actually plan my fuel ups so I am almost empty when I travel to Utah. If I have too much fuel in the tank and its boiling I am unable to fill up until the temp lowers. I can continue on my journey with fresh cool fuel. Otherwise I'm stuck for an hour or so. I have changed the gas cap, charcoal canister, and plugs as well. I've also applied heat shield. None of that has worked. I just ordered my pre cat sensors. I'm hoping that will solve the problem. If not I may have to get rid of the old girl. I'm over dealing with this problem. I'm optimistic that this will work though.

If you can please definitely give an update if the pre cat sensors work out. Since you’ve seen to do all of the other mods already it would be pretty interesting to see the outcome. If it solves the problem you may have struck gold

 

[CCFDCAL]

I'm curious if anyone has made any progress. The temps in Vegas hit the high 90's for a couple days and I've already had an issue. I was able to restart my rig after about 10 minutes, but still. I haven't had a chance to put new O2 sensors in, but now after talking to quite a few mechanics, I'm not optimistic that will solve anything. I'm still going to replace them since I bought them and can't return them now.

I'm intrigued with this idea of putting a power steering cooler on the fuel return side. Has anyone given this a shot. It still doesn't answer the question why this is happening, but at this point I almost don't care if it solves the problem.

 

[8lifgr8]

I'm curious if anyone has made any progress. The temps in Vegas hit the high 90's for a couple days and I've already had an issue. I was able to restart my rig after about 10 minutes, but still. I haven't had a chance to put new O2 sensors in, but now after talking to quite a few mechanics, I'm not optimistic that will solve anything. I'm still going to replace them since I bought them and can't return them now.

I'm intrigued with this idea of putting a power steering cooler on the fuel return side. Has anyone given this a shot. It still doesn't answer the question why this is happening, but at this point I almost don't care if it solves the problem.

We've only hit 80F (at 5200ft) and did some serious 4-wheeling in 4-lo (but ambients were only mid 60s at the time). White Rim in early June will tell me more, but so far so good, only a normal/brief hiss at the pump so far after doing the plugs and the o2s.

 

[2001LC]

I'm curious if anyone has made any progress. The temps in Vegas hit the high 90's for a couple days and I've already had an issue. I was able to restart my rig after about 10 minutes, but still. I haven't had a chance to put new O2 sensors in, but now after talking to quite a few mechanics, I'm not optimistic that will solve anything. I'm still going to replace them since I bought them and can't return them now.

I'm intrigued with this idea of putting a power steering cooler on the fuel return side. Has anyone given this a shot. It still doesn't answer the question why this is happening, but at this point I almost don't care if it solves the problem.

Listing year, miles and any aftermarket parts. i.e bumpers, slider, skids, rack, winch, etc. Help all here, get better understanding of your rig. You can just add all, to your signture line.

You mention a few things you tried. But I did not see, some of the key points, which should be first as PM. If you began reading the first post here. You know I'm big, on getting basics inline first. We'll spin are wheel endless if not.

#1 PM is Coolant system service. I find so many in a mess. Why in a mess. Improper service or PM (preventive maintenance).

1. Clogged radiator fins. They need washing every ~5K or after long dirty roads, driving through bug swam, cotton wood, grasses, weeds, birds, etc. I've even found large sheet of Styrofoam blocking radiator fins.
2. Coolant reservoir empty.
3. Coolant res hose blockage.
4. Coolant res hose curled upward.
5. Bad or importantly installed thermostat.
6. Bad radiator cap.
7. Not flushing with block draining and or using improper coolant.
8. Low coolant.

Just some of the other areas of concern:
What is your ECT (engine coolant temp) during various drive condition and different OAT. Gauge on dash is near useless in most.
What are your fuel trims, during various drive condition. Most revealing, when boiling fuel and when driving on flat road/HWY cruising at 55 to 65 MPH.
Have all vacuum leaks be stopped. Fuel trims can be revealing here.
Fuel filter.
Weak fuel pump. (runs lean, HOT)
Weak FPR. (runs lean, HOT)
Clogged fuel filter, soak or injectors. (runs lean, HOT)

 

[CCFDCAL]

Listing year, miles and any aftermarket parts. i.e bumpers, slider, skids, rack, winch, etc. Help all here, get better understanding of your rig. You can just add all, to your signture line.

You mention a few things you tried. But I did not see, some of the key points, which should be first as PM. If you began reading the first post here. You know I'm big, on getting basics inline first. We'll spin are wheel endless if not.

#1 PM is Coolant system service. I find so many in a mess. Why in a mess. Improper service or PM (preventive maintenance).

1. Clogged radiator fins. They need washing every ~5K or after long dirty roads, driving through bug swam, cotton wood, grasses, weeds, birds, etc. I've even found large sheet of Styrofoam blocking radiator fins.
2. Coolant reservoir empty.
3. Coolant res hose blockage.
4. Coolant res hose curled upward.
5. Bad or importantly installed thermostat.
6. Bad radiator cap.
7. Not flushing with block draining and or using improper coolant.
8. Low coolant.

Just some of the other areas of concern:
What is your ECT (engine coolant temp) during various drive condition and different OAT. Gauge on dash is near useless in most.
What are your fuel trims, during various drive condition. Most revealing, when boiling fuel and when driving on flat road/HWY cruising at 55 to 65 MPH.
Have all vacuum leaks be stopped. Fuel trims can be revealing here.
Fuel filter.
Weak fuel pump. (runs lean, HOT)
Weak FPR. (runs lean, HOT)
Clogged fuel filter, soak or injectors. (runs lean, HOT)

First Off, Thanks for taking the time to respond and so thoroughly. I have been following this thread since the beginning, but I think I've made some assumptions about the condition of my rig without a thorough check. I"m going to revisit the coolant system before I do anything drastic.

Well it looks like I have some homework to do. I'll report back.

 

[2001LC]

First Off, Thanks for taking the time to respond and so thoroughly. I have been following this thread since the beginning, but I think I've made some assumptions about the condition of my rig without a thorough check. I"m going to revisit the coolant system before I do anything drastic.

Well it looks like I have some homework to do. I'll report back.

Hope it helps! Starting at basics. is so important!

Again I'll encourage you, to add your vehicles info to signature line. I did see in another thread you've an 07. But I assure you I'll not remember that. Nor do I know miles, stock or a heavily built. It matters! Adding once to your signture or type into each post, when asking for help. 06-07 have very special issues. With the USA & Canada 100 series we've 5 different variation.

Look at my signature line. You can click on master link and you'll find a lot of useful link.

 

[gatormark91]

This is happening to me to with the same conditions. I never have an issue until the hot temps in Las Vegas come around. I actually plan my fuel ups so I am almost empty when I travel to Utah. If I have too much fuel in the tank and its boiling I am unable to fill up until the temp lowers. I can continue on my journey with fresh cool fuel. Otherwise I'm stuck for an hour or so. I have changed the gas cap, charcoal canister, and plugs as well. I've also applied heat shield. None of that has worked. I just ordered my pre cat sensors. I'm hoping that will solve the problem. If not I may have to get rid of the old girl. I'm over dealing with this problem. I'm optimistic that this will work though.

Get a piece of hose and a couple of vacuum tube connectors. Bypass the VSV on the intake manifold so the charcoal canister sees vacuum all the time. You'll likely get some codes thrown, but they don't affect how the truck runs. See if this helps (don't leave it like this forever, of course, and make sure the connectors are properly secured with clamps so you don't get gas vapor roaming free under the hood). If it does help, get a new VSV. If it does not, look at a weak fuel pump for the culprit.

 

[J1000]

I'm curious if anyone has made any progress. The temps in Vegas hit the high 90's for a couple days and I've already had an issue. I was able to restart my rig after about 10 minutes, but still. I haven't had a chance to put new O2 sensors in, but now after talking to quite a few mechanics, I'm not optimistic that will solve anything. I'm still going to replace them since I bought them and can't return them now.

I'm intrigued with this idea of putting a power steering cooler on the fuel return side. Has anyone given this a shot. It still doesn't answer the question why this is happening, but at this point I almost don't care if it solves the problem.

Search for my posts in this thread and the other one about the truck catching on fire. I solved this problem. My fuel doesn't get over 20F higher than ambient. Just got back towing across country 30 hours fuel never went above 105F. I actually have a fuel temperature sensor.

I added heatshields and a power steering cooler on my return line. Stopped posting in this thread because people kept insulting me.

 

[JJ_SC]

Unfortunately, I ran into this issue for the first time on my last trip. Death Valley, 91 degrees outside temp. We went from below sea level to about 4000ft in only a few miles. Not a super hard trail, but steep and slow the whole way. By the time we got to the top I could smell fuel and hear it boiling in the tank. I let it sit for about 45 minutes and all was fine again.

I've had the truck since new. 06, (mod in signature) with ~160k miles. I've always kept to factory maintenance schedule and my mechanic is a certified Toyota mechanic who started his own independent shop. But, he's not a Land Cruiser guy specifically. Coolant system has been flushed per Toyota's maintenance schedule and done with Toyota coolant. I don't notice any vacuum leaks and the lines/hoses all seem to be in good shape.

After that trip, and based on reading posts from @2001LC, I started monitoring ECT and fuel trim while driving. Basically it runs about 190 - 196 with the long term fuel trim around 3-7% at freeway speeds and they drop to less than 1% at idle (in the In-N-Out drive through line.) Admittedly, I don't really know what those are supposed to be reading and I'm also not sure what normal temp is for the 06-07s. Seems like maybe they run a little hotter?? On a recent 4 hour highway trip with outside temps in the mid 70s to low 80s, ECT stayed close to 190 most of the time. Up a few steep grades it increased to around 197 - 200. I don't think it ever went above 200.

I am planning to do the following: hose the radiator fins, replace the charcoal canister (I have always topped off, but will break that habit now) and install a heat shield next to the fuel lines. I am also replacing the exhaust with the Borla SS cat-back set up. The stock muffler is pretty shot but doesn't have any actual holes in it.

Any additional input or suggestions would be appreciated! Cheers.

 

[J1000]

On the rear-passenger corner of the fuel tank it comes closest to the exhaust as it starts to go up and over the rear axle. There is no factory heatshielding in that spot, but there is on the rest of the fuel tank. One of the most effective things I did to lower fuel temperature was place a small piece of adhesive heatshield on that spot.

Heatshield material: https://www.amazon.com/Thermo-Tec-13575-Adhesive-Aluminized-Barrier/dp/B00029KC2K?tag=ihco-20

I was actually towing 60 hours, 30 hours was the return trip with Toyota pickup on the trailer. Denver to Myrtle Beach and back right through the muggy south.

 

[slacker24-7]

Is there a difference in number of cases between 98-02 vs. 03-07 models with the evap canister location moving from engine compartment to under vehicle?

Mine is a 01 and Ive had it happen At lower elevations in the Utah and Arizona heat a few times over the years, as well at elevation , I’ve never experienced it here in Ark. I’ve put a heat shield on it that helped, but last summer in 115 degree Utah heat it was even boiling in my fuel filter . Ya just can’t open the fuel cap. Shutting it down and letting it cool eventually stops the boil, but it’s spooky. I have a buddy in Phoenix that won’t drive his 04 100 out to run with us if it’s summer temps. He drives his tundra and lets the 100 sit

 

[silver02accord]

i had the gas tank vent vapor this past week. we drove 13 hours straight from san diego to canyonlands and then did the last 1-1.5 hr in 4lo over elephant hill. temps were in the mid 80s and i didn't smell it until about 45 minutes into the drive. i have full asfir skids( i will post a pic for 2001lc to see). i didn't have time to plug in my reader to get engine temps BUT the 06 lx seems to run well within specs and was running at 181 deg when i checked in on it after several hours of driving in the mid 80s. it usually runs at 185, haven't seen it above 191 since i replaced tstat, cleaned radiator, new rad hoses, new reservoir hoses, new rad cap. it took a while to vent out -maybe an hour after it was shut off. i have yet to install a heat sheild and wrap but will do so soon(sitting in the garage)

 

[OwnerCS]

I've used a product named DEI cool tape (flex conduit and tape) to wrap wiring and hoses that are near exhaust components.

 

[JJ_SC]

I added a heat shield between the catalytic converter and the fuel lines today. I also wrapped as much of the fuel and vapor lines as I could in the engine compartment. Tomorrow I’ll pull the old exhaust and see what I can do about a shield between the muffler and that gas tank. Then, install the Borla exhaust. The muffler is significantly skinnier than stock, so that should help. Replace the charcoal filter, then after that, I’ll tackle the radiator and see if I can get it running a bit cooler.

My daughter is stealing it for a 3 week trip in July and I’ll be hauling the whole fam to Moab in September. I hope this works, cuz I don’t want to have to stress it!

 

[JJ_SC]

Pics: