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

[2001LC]

G

it's never a good idea to vent your tank with the cap. You wouldn't do it at the radiator, but people do it with a the other tank filled with flammable liquid with a higher than 1 ATA layer of gas on top lol.
At that point I think you can throw out any volume/temp and pressure calculations. Or the ppo2.
It's just bad all around.
Let it idle. It' might not cool faster but there won't be any shooting at the thermo nuclear weapons.

@jerryb do you have logs on your 06LC ECT, FT, IAT and trans temps? Can you post here, perhaps again!

 

[CUBuffs]

it's never a good idea to vent your tank with the cap. You wouldn't do it at the radiator, but people do it with a the other tank filled with flammable liquid with a higher than 1 ATA layer of gas on top lol.
At that point I think you can throw out any volume/temp and pressure calculations. Or the ppo2.
It's just bad all around.
Let it idle. It' might not cool faster but there won't be any shooting at the thermo nuclear weapons.

good point! although anytime I'm refueling in the summer at higher altitude would be a similar situation..

 

[jerryb]

paul, I can say this.
I don't tow anything, there aren't many hills around here.
my coolant temp is never above 194.7F
my intake air temp is always above 110F, if not 115F, between 85-105F ambient.
My S fuel trim is always within +5 or -5 when and if I see it. LT is always negative of zero but less than -3. I see that a lot also
I don't do anything that's going to affect transmission fluid temp. I rarely look at it. I have the part time kit and I don't do 4 lo. not in the last year at least. I've been distracted lately monitoring sensor voltage, I've deleted my cats, for the time being.
Tranny temp is not on my main screen on my phone while driving.
six months now has been all stop and go in the city. No freeway 300 mile treks.

 

[d4nvu]

Wow one more dangerous thing I found under the truck today while crawling around... when I had the tank replaced it seems they pinched one of my fuel lines. Dangerous for sure and very audible hiss coming from the line.. I can’t believe I’ve been driving like this for 8 months. Another thing to replace.

 

[2001LC]

Good point! although anytime I'm refueling in the summer at higher altitude would be a similar situation..

Valid counterpoint.
But also consider when fueling, it's typically when tank at 1/4 full or less. Makes me wonder if when venting (removing cap) with higher level of fuel in tank. That the "shut off" (roll over valve) valve may get pushed shut by expanding fuel. That heat expansion and some gunk from boiling, it may be sticking. Then as you sit and cool down. Valve drops back free up EVAP circulation.

"Pure speculation on my part" But is is one think I've been considering, as to why full tanks have the issue and 3/4 or less do not boil.

The water in your fuel really has me scratching my head. With blended fuels, that's usually not and issue.

Here's pictures of your fuel tanks' valves Dan.

paul, I can say this.
I don't tow anything, there aren't many hills around here.
my coolant temp is never above 194.7F
my intake air temp is always above 110F, if not 115F, between 85-105F ambient.
My S fuel trim is always within +5 or -5 when and if I see it. LT is always negative of zero but less than -3. I see that a lot also
I don't do anything that's going to affect transmission fluid temp. I rarely look at it. I have the part time kit and I don't do 4 lo. not in the last year at least. I've been distracted lately monitoring sensor voltage, I've deleted my cats, for the time being.
Tranny temp is not on my main screen on my phone while driving.
six months now has been all stop and go in the city. No freeway 300 mile treks.

194.7F sound okay for the hotter days of 105F, but on high side for a stock cruiser (not built). Have you cleaned your radiator fins and service coolant system?

I see LTFT here in mile high city, closer to +2.5 - 5.5, never 0 to -3. Doesn't negative LT means EUC correcting for rich ST condition!
Are you using spark plug extenders on the A/F and o2s, while CATs out?

Dan's is FT are interesting, as his logs show he's runs 0-2.5 LTFT in his 07.

 

[abuck99]

Valid counterpoint.
But also consider when fueling, it's typically when tank at 1/4 full or less. Makes me wonder if when venting (removing cap) with higher level of fuel in tank. That the "shut off" (roll over valve) valve may get pushed shut by expanding fuel. That heat expansion and some gunk from boiling, it may be sticking. Then as you sit and cool down. Valve drops back free up EVAP circulation.

"Pure speculation on my part" But is is one think I've been considering, as to why full tanks have the issue and 3/4 or less do not boil.

The water in your fuel really has me scratching my head. With blended fuels, thats ussal not and issue.

Here's pictures of your fuel tanks' valves Dan.
View attachment 2404753
View attachment 2404755

194.7F sound okay for the hotter days of 105F, but on high side for a stock cruiser (not built). Have you cleaned your radiator fins and service coolant system?

I see LTFT here in mile high city, closer to +2.5 - 5.5, never 0 to -3. Doesn't negative LT means EUC correcting for rich ST condition!
Are you using spark plug extenders on the A/F and o2s, while CATs out?

Dan's is FT are interesting, as his logs show he's runs 0-2.5 LTFT in his 07.

Paul- Look how clean all the fittings/brackets/components are at the top of your tank- I don't think the valve has build up or sticking based on what I see there.

 

[jerryb]

pure gasoline expansion rate is so low it's not going to do anything. It's the layer above that has a direct relationship with pressure and temp.
ethanol absorbs water 50 times faster than gasoline

and to look up fuel thermal expansion I see a 1% increase with a 20 degree rise. figure a 15 gallon increase from a temp of 90 F to 110F and get a .15 gallon bump. BTU's doesn't change though.

at the same time the gas layer above the fuel is pressed higher.
(all assuming it's a closed container that doesn't expand, ,, much..) it will expand, we know that. Also we know removing the cap, like in that video can at some point start a fire, And, depending on gas make up, volatility and the partial pressures of that make up it can ignite spontaneously.

at some point the boiling could be happening in the tank or in the lines. Hopefully the cooling affect of the fuel traveling in the loop will cool the fuel in the tank and the pump and the metal container. I don't think people realize how fast fuel is traveling though those lines.
Picking out a spot where it may be getting hotter than normal and putting a band aid on it may or may not be just enough to keep it one degree closer to acceptable. Just like using non ethanol.

don't forget there isn't any back pressure on the return line past the fuel regulator above the ambient pressure of the gas layer in the fuel tank. There is some bleed off though. That's the fuel bleed off spec for five minutes at 21psig
There will be pressure on the feed line starting at the pump from the cheapy check valve, but it will all equalize pretty fast, couple hours.
What you can hear is gas and fuel traveling through the lines when you shut your car off. The gas bubble is what's making noise.


I only care about the trim if it's out of hand.. CEL light comes on at 35. To me, 10 is a big deviation from my normal running numbers.
just because someone sees a +10 or -10 doesn't mean something is wrong. But in a wide sense of diagnostic tools it could point to a problem somewhere else, aging components, unmeasured air, leaking air, bad air temp etc.
There isn't something necessarily wrong with a car that has has higher LT trim numbers than another identical car. It'd be foolish to think that two identical cars 1000 miles away from each other should exhibit the same numbers.

the front airflow sensors, or o2 sensors in earlier years are before the cat. they don't care if it's there.
I have a urd calibrator on my rear narrow band sensors. I do see a 150 F drop in temp at the 2 bolt flange on the midpipe. (first 2 bolt falnge after the 3 stud header flange)



we already agree to disagree about coolant temp. I don't want mine to run less than what it does.

if cylinder head temp rises then coolant temp rises. That was good enough for them as they didn't include a CHT sensor.
I can't see how dropping coolant temp a few degrees has any affect on CHT or EGT or that a correlation exists between EGT and fuel temp. There was some reference to that earlier in this thread or another one.
The fact is, all our CHTs and EGTs are going to be different just like fuel trims. Different environments, different fuel qualities, and different states of tune and maintenance. All running on different fuel air temp knock maps.

I don't believe there is any relationship between normal operating temp threads and why is my fuel boiling threads.
I'd be more interested in seeing oil temp than thinking a 200F coolant temp is out of bounds.



I'm thinking about putting an oil sensor spacer ring on the filter housing.

 

[2001LC]

Paul- Look how clean all the fittings/brackets/components are at the top of your tank- I don't think the valve has build up or sticking based on what I see there.

Yeah I saw that first picture of a valve look fairly clean. I took pictures in the blind, and viewed later zooming in on picture (s) on my PC. I can't see very clearly, as isn't great res picture.

I suppose it would be self cleaning, as fuel enters and slushes around. But can't say it looks as clean as new, and seems to have a little residue on it. Nor would I expect gunk like seem on fuel door with dust attached to it. I now wished I'd pushed in up, too see if it stuck. I think that one is on fill tube, and a 3rd connected via hard line.

The second valve pictures above, seems to be separate from frist & 3rd. There is a 3rd valve or sensor. It appears connected via a hard tube to the first (shut off valve) fill tube

I've looked at parts diagram for this 2007. I do not see the first valve pictured above, as being sold separate from fuel tank. But it looks like a rollover shut off valve.



Here's the another (3rd) sensor, valve or breather of some sort in the tank the 07.

We need some old tanks (98-02, 03-05 and 06-07) to rip apart. Preferable of one with fuel boiling issue.

 

[2001LC]

pure gasoline expansion rate is so low it's not going to do anything. It's the layer above that has a direct relationship with pressure and temp.
ethanol absorbs water 50 times faster than gasoline

and to look up fuel thermal expansion I see a 1% increase with a 20 degree rise. figure a 15 gallon increase from a temp of 90 F to 110F and get a .15 gallon bump. BTU's doesn't change though.

at the same time the gas layer above the fuel is pressed higher.
(all assuming it's a closed container that doesn't expand, ,, much..) it will expand, we know that. Also we know removing the cap, like in that video can at some point start a fire, And, depending on gas make up, volatility and the partial pressures of that make up it can ignite spontaneously.

at some point the boiling could be happening in the tank or in the lines. Hopefully the cooling affect of the fuel traveling in the loop will cool the fuel in the tank and the pump and the metal container. I don't think people realize how fast fuel is traveling though those lines.
Picking out a spot where it may be getting hotter than normal and putting a band aid on it may or may not be just enough to keep it one degree closer to acceptable. Just like using non ethanol.

don't forget there isn't any back pressure on the return line past the fuel regulator above the ambient pressure of the gas layer in the fuel tank. There is some bleed off though. That's the fuel bleed off spec for five minutes at 21psig
There will be pressure on the feed line starting at the pump from the cheapy check valve, but it will all equalize pretty fast, couple hours.
What you can hear is gas and fuel traveling through the lines when you shut your car off. The gas bubble is what's making noise.


I only care about the trim if it's out of hand.. CEL light comes on at 35. To me, 10 is a big deviation from my normal running numbers.
just because someone sees a +10 or -10 doesn't mean something is wrong. But in a wide sense of diagnostic tools it could point to a problem somewhere else, aging components, unmeasured air, leaking air, bad air temp etc.
There isn't something necessarily wrong with a car that has has higher LT trim numbers than another identical car. It'd be foolish to think that two identical cars 1000 miles away from each other should exhibit the same numbers.

the front airflow sensors, or o2 sensors in earlier years are before the cat. they don't care if it's there.
I have a urd calibrator on my rear narrow band sensors. I do see a 150 F drop in temp at the 2 bolt flange on the midpipe. (first 2 bolt falnge after the 3 stud header flange)



we already agree to disagree about coolant temp. I don't want mine to run less than what it does.

if cylinder head temp rises then coolant temp rises. That was good enough for them as they didn't include a CHT sensor.
I can't see how dropping coolant temp a few degrees has any affect on CHT or EGT or that a correlation exists between EGT and fuel temp. There was some reference to that earlier in this thread or another one.
The fact is, all our CHTs and EGTs are going to be different just like fuel trims. Different environments, different fuel qualities, and different states of tune and maintenance. All running on different fuel air temp knock maps.

I don't believe there is any relationship between normal operating temp threads and why is my fuel boiling threads.
I'd be more interested in seeing oil temp than thinking a 200F coolant temp is out of bounds.



I'm thinking about putting an oil sensor spacer ring on the filter housing.

Thanks for info Jerry.

We do agree on fuel trim. It's the constant adjusting by ECU that makes, modern systems so superior to carburetor. Gone are the days of changing carb jet to adjust for altitude. The only reads of any importance are when engine RPMs steady.

Only a few things I feel certain of, with subject at hand:.

1) Blended fuel, is issue in what is cause fuel boil (excessive tank pressure)

2) Engine running hot, as seen by monitoring ECT. Is a factor in this fuel boil issue. Of this I have no doubt!

3) That Belly Pans apparently trap heat from CAT. I've some logs before and after a belly pan & skids install. They clearly show a rise in ECT after belly pan and full skids installed.
Additionally as Dan has stated, and as pictures I posted shows. His wire housing, is damage by what looks like heat damage. Only in area or tunnel created by belly pan near the CAT.

4) Placing heat shield(s) between CATs and fuel lines is reducing if not eliminating fuel boiling issue.
Aftermarket heat shield should not be necessary on a stock rig. Also looking at @abuck99 as example of a well tune proper running heavy built 2005LC, with full belly pans and skids. He does not need extra heat shield. He drives from GA, thur states like OK, TX, NM to CO in the sumner, and hits many high mtn trails. He uses whatever gas the station offer. He fills his fuel tank. He does not have this fuel boil issue. His ECT is only slightly elevated from what I see in 98-02 stock igs.

So again I'll say, get basics in line first. ECT is a good indicator of basics, in line, as is fuel trims.



For now what I'm really tried to find out: Do we have variation in normal ECT, which gives us operating temp, based on year.

In 98-02, I'm sure, at evation of 5K to 8.5K ft above sea level. ECT of 184 to 187f is normal for OATs of 77f to 97F with full sun. Seems even at sea level or 12K this would not vary to much. But as we go higher air is thinner. So engine runs leaner. ECU corrects fuel delivery (fuel injector modulation) get a stoichiometric 14.7 to 1.

 

[Skidoo]

In 98-02, I'm sure, at evation of 5K to 8.5K ft above sea level. ECT of 184 to 187f is normal for OATs of 77f to 97F with full sun. Seems even at sea level or 12K this would not vary to much. But as we go higher air is thinner. So engine runs leaner. ECU corrects fuel delivery (fuel injector modulation) get a stoichiometric 14.7 to 1.

That increase in altitude also means lower air pressure which changes boiling points, using water as an example at sea level it boils at 212F, at 12,000 feet however, it boils 190F so at a 10% lower temperature. From an earlier post we know E10 has a 10% lower boiling point than non-ethanol gas. So both altitude and temperature are factors in fuel boiling and probably sum together. So how close to the EVAP system design limits is E10, are some heat shields enough to keep it inside the limits.

 

[jerryb]

I never had the boiling issue before a heat shield either. I did put it on because it's easy, and you can do it without taking anything apart.
I did have fuel boiling when I first bought it. After a fuel pump change it was gone. Then all the cooling components a year to 18 months later.
My coolant temp changes did not go down from 207F to 194.xxF until after a radiator change around 18 months or so after I was messing with fuel pumps. My coolant temp didn't affect my fuel temp at all. And it shouldn't. Not in a my fuel is boiling kind of way.



But as we go higher air is thinner. So engine runs leaner. ECU corrects fuel delivery (fuel injector modulation) get a stoichiometric 14.7 to 1.

The higher the altitude the richer the engine runs if nothing else is changed.
The changes happens so fast you probably can't even watch it. Everything working correctly, that in itself shouldn't affect egt or cht and it certainly doesn't affect ect. If egt was affected it'd be negligible, just a blip or another slow curve.
The afr is a commanded number. It's not necessarily 14.7/1 most often it isn't.

 

[NearJetties]

At what point does this become a recall worthy issue for Toyota? Is there an avenue to report this to them?

not that they should replace the entire cooling system but engineering insight into what specifically is causing this issue and perhaps an official fix for the evap/pressure management system/heat shielding is in order. It wouldn’t be the first major recall involving fuel tanks on Cruisers.

 

[Skidoo]

At what point does this become a recall worthy issue for Toyota? Is there an avenue to report this to them?

not that they should replace the entire cooling system but engineering insight into what specifically is causing this issue and perhaps an official fix for the evap/pressure management system/heat shielding is in order. It wouldn’t be the first major recall involving fuel tanks on Cruisers.

Or do we sue the EPA / Congress for legislating E10 knowing that its evaporative loading could be at or outside the design of vehicles at high altitude / temperature.
Legislating is not engineering, EPA granting a waiver for E10 shows they knew its evaporative loading was higher.

 

[abuck99]

Or do we sue the EPA / Congress for legislating E10 knowing that its evaporative loading could be at or outside the design of vehicles at high altitude / temperature.
Legislating is not engineering, EPA granting a waiver for E10 shows they knew its evaporative loading was higher.

Get in line- the AMA has been fighting it for years and are a well organized grass roots organization that has barely been able to move the needle, ethanol lobby is formidable, our trucks will be in recycle before a case is brought before congress.

 

[2001LC]

At what point does this become a recall worthy issue for Toyota? Is there an avenue to report this to them?

not that they should replace the entire cooling system but engineering insight into what specifically is causing this issue and perhaps an official fix for the evap/pressure management system/heat shielding is in order. It wouldn’t be the first major recall involving fuel tanks on Cruisers.

Coolant system is fine as designed. It just most 100 series on the road today; have not been properly PM thur service history. Many miss the fact Toyota state's; wash the radiator fins. Or run old or non OEM rad. cap and/or thermostat, or have not properly flushed and topped coolant system. Fan clutch (FC) needs consideration also. I find some FC incredibly difficult to make the call on.

If we can find some part, component or system design is unable to handle this blended fuels. Than we can take to Toyota and DOT. But date USA enacted blended fuel, would be key to any recall.

We have to prove this out in a stock rig. Once 100 series modify, driven overweight or towing limits. Toyota can wash their hands of it.

So far on pure stock rigs. Which I've only been looking at this issue for a few weeks. I've gotten 98-02 stock fuel boiling issue resolved. By resolving coolant system issues. In those 89-02 I've gotten ECT down to 184 to 187F range in OATS up to 97F and sunny.

In Dan's 2007 ( @CUBuffs ) I only drop ECT, at best 2F. We've not found what is keeping its ECT higher than I fell normal yet. But by looking at old logs of Merlot before and after full belly pan (BP) and skids, it did raise ECT with the addition. In Dan's once we've exhausted coolant system and fuel trims concerns. I'd like to swap out the belly pan. See than if we get a drop in ECT. Biggest issue is time, as fall is approaching. We need summer heat.

 

[2001LC]

Did another 98 coolant system service. Was with timing belt R&R. This 98LC has 275K on it. It also has some non stock mods and parts. No reports of fuel boiling or signs at gas cap area (gunk).


Pre service 190-201 F.
Post service 187-192 F.
OAT ~90F. Sunny (pre was 6PM, Post was 2:30PM hotter sun)

So this post service ECT, was ~3 to 5F higher than other pure stock with foam on 3 side of radiator. Was it mods, lack of foam or combo resulted in a higher ECT than the 184 to 187F I've been seeing in 98-02!

Mods:
Snorkel.
Aluminum #1 skid extends extra ~12" to No.3 crossmember, with less air catching & venting ability. But very cool looking
Sliders.
Radiator aftermarket of questable design. No foam and misaligned fan shroud and reservoir bolt hole.
Intake manifold was loose sucking air (major vacuum leak), for great than 25K miles. Also sucking dust, not good!
1 PCV hose bad (vacuum leak).
Air filter seal curled, sucking dust. Not good!

 

[Skidoo]

It is interesting that ethanol was forced on us as a renewable fuel. There are other renewables, even other alcohols. The alcohol that makes the most sense is butanol and when it is combined with gasoline does not lower the boiling point of the fuel.
Wikipedia - Butanol at 85 percent strength can be used in cars designed for gasoline (petrol) without any change to the engine (unlike 85% ethanol), and it contains more energy for a given volume than ethanol and almost as much as gasoline, and a vehicle using butanol would return fuel consumption more comparable to gasoline than ethanol blend.
Butanol can made by fermentation processes or can be made by converting ethanol. But the ethanol lobby wanted to maximize their profits rather than do the right thing.

 

[JunkCrzr89]

At what point does this become a recall worthy issue for Toyota?

I can’t imagine this would go anywhere on a 20 year-old vehicle. Especially since this thread exists demonstrating the importance of maintenance (or the lack thereof) to the problem. Hell, Toyota never issued a recall for the hundreds of thousands of 95-04 Tacomas that had severe frame rot and frame breakage... I’m not a lawyer, but @Skidoo suggestion about E10 litigation sounds like It has substantial merit.

 

[abuck99]

Also- there's evidence that blended ethanol content is often more than 10%- major producers are fully aware of it. This can have significant effect on fuel boil especially in summer months.

 

[nsaladin]

Does anyone hear gurgling like sound coming from the fuel tank area when idling? I hear my tank gurgle, and turn the engine off, it instantly goes away.

Brand new fuel pump, new fuel filter, new gas cap.

coolant temp: 194with A/C at idle @5900 ft elevation.

I have had similar issues to as described by lots of posts in this thread with fuel smell, gas puking out at higher altitude trailheads, but this was all prior to replacing cap, pump, filter. Went to altitude (10,500’) on Jones pass yesterday and only heard the gurgling when idling, no fuel smell, or puking out.