Gas tank building excessive pressure & fuel smell. Dangerous for sure! Why does this happen? (14 Viewers)

[2001LC]

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

Edited 3/15/25:
Since first posting this thread. I've corrected many boiling fuel. By working in this order:

1. Coolant system if first on the list, must be operating as designed. Which radiator fins cleaning is key.
2. Engine tune, so it's running at peak, is a must.
3. EVAP system must be work as design. Which I find all 03-05 and 70% of the 98-02 boiling fuel, have bad Charcoal canister.
4. Built rigs, especially with belly pans. Are directing heat onto: fuel & EVAP line and onto fuel tank. Shielding, air diverts/channeling air where wanted and extra air holes. Can help reduce, preheating fuel.
5. 03-07, understanding the causes that flood the charcoal canister and eliminating them. Such as: Over topping fuel tank, topping on hot days, paking after topping on hot day and or at angle (Think teapot spout) and topping fuel tank before asscenting a pass.
6. Overheating engine (Note AT fluid overheating contributes), for any reason. must be corrected.
7. Replacing, charcoal canister. Do it last, to reduce chances of contaminating another.

Edited 7/4/20:
Charcoal Canister! What I found in most every case of "fuel boiling", that I've worked on. Was in most, the engine was running hot (over 200f). That once the issue contributing to running hot (coolant system, engine & A/T fluid), brought back to factory spec. The Charcoal Canister (CC) then needed replacing, in most all 03-07 and many of the 98-02.

Charcoal Canister replacement is number one, in curing fuel boiling. We must correct what caused CC to become saturated (clogged) with raw fuel in the first place or risk damaging the replacement CC.

Edited 12/29/23:

Once fuel tank overflows. We dump, raw fuel into Charcoal Canister (CC). In models where CC in rear near gas tank, as in the 03-07 100 series. This happens very easily! Whereas 98-02 100 series, the CC in engine compartment, they're more forgiving. But all CC, will become saturated.

Once a Charcoal Canister is saturated, it must be replaced!

The CC will soak up and retain fuel, just with time/miles. But in a well maintained 100 series, this takes a very long time.

I've found, after all done to correct fuel boil. Be it correcting hot running engine, hot transmission fluid, shielding excessive radiant heat, stop over filling gas tank, fault in EVAP system or any combination. Charcoal Canister, must be replace as a final step!

A sure sign of bad CC, is putrid smell. Like old gas, that has gone bad sitting in a gas can for years. This however is later stage, once Charcoal so saturated, it can't soak up fumes any longer.

These saturated CC, are noticeable heavier than a fresh new OEM. Due to raw fuel, it has soaked up contaminating and clogging them.

If CC clogged, the fuel tank builds excessive pressure.

We must corrected reason, Charcoal Canister was contaminated in the first place, before replace CC. Or we risk damaging CC again."

Number one reasons, the 03-up CC become contaminated:
1) Topping fuel tank, by adding more fuel after "auto shut-off" of filling station pump handle.
2) Fill to auto shut-off, on very hot sunny day, then parking. Not driving to draw down fuel level. Fuel then heat and expands in gas tank and into CC.
3) Topping to auto shut-off, then ascending a rocky road.

A sure sign of fuel boil an CC contaminated: Gas cap area crudy looking.
This 07 with only 24K miles. CC was badly contaminated.

07 w/170K, with Slee belly pan tonnulling heat of exhaust to fuel lines and fuel tank. You can bet the CC is bad.

Original post:

Please report your ECT (engine coolant temp) here. The info, will be very valuable. Whether or not, having this issue of fuel boiling. Other data points; 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 seem, 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. The used CC may not have be a good option. As it could be contaminated.

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. Also, 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 tank at 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) above, 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 what is 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

 

[2001LC]

This post #2, is a work in progress as time allows I'll add to it!. So keep checking back.

Here's 99LC I'm attempt to solve of fuel tank pressure and fumes issue on. I began with the basics to correct issue.

Basic's being: Air, fuel and cooling of the engine. I explained to Gavin, we need to first make sure engine is operating properly. Unfortunately I did not test drive or run scan before beginning the work.

So I pulled engine cover and took a look around (visual inspection).

Intake AIR & Vacuum:

• Air filter box with a K&N filter (not clogged) and 1 of 4 fastener missing (busted off). -- Oily MAF.
• The air tube had been glue together. -- Possible blockage and or Vacuum leak within.
• The rear air pipe vacuum line (~8") was past useful-life, as most I see. -- Vacuum leak.
• The idle up control vacuum line at air pipe was past useful life. -- Vacuum leak.
• The charcoal canister (CC) was from a local Toyota salvage yard. -- Questionable condition.
• Vacuum line from intake manifold VSV to CC was loose fitting. -- Vacuum leak.
• PCV hoses both cracked and grommet hard as a rock with loose fitting PCV valve.-- Vacuum leak.
• Oil around head covers, likely gaskets leaking. -- Vacuum leak (well kind of)

Fuel.

• Costco primary source of premium fuel
• Fuel filter was newer OEM.
• Gas cap newer OEM.
• No fuel leaks observed.
• Fuel pressure regulator factory installed (aged)
• No raw fuel smells.

Cooling:

• Engine was hot, so I could not remove the NON OEM radiator cap. Some white dried film around top of radiator.
• Lower radiator hose had screw clamp. Nut on thermostat housing cap, damage from improper wench use and over torquing.
• Coolant reservoir was near full line with red coolant, and it's draw tube was straight.
• Heater Tees had pink crusty on them at hose.
• No other trials of pink/red crusty and no real pink/red crust signs of coolant leak.

Other observations:

• Holes in Muffler.
• Fuel tank skid shield old grimy oily look. Could be long term fuel drenching attracting grim, or could be totally unrelated. Would expect some surface rust from mag chloride or just clean painted metal.

No raw fuel smell around fuel tank or anywhere (cold siting in garage).

So I dug in:

Work begins, making sure basic all in order. I so often find many issue under the hood, in rigs with even with the best service history. The top finds are; coolant issues, vacuum leaks, loose spark plugs (<<<Link), leaky head cover gaskets, low transmission fluid, improperly routed wires and hose, missing retain & guide clamps along with fluids like oil, power steering and brake fluid needing proper PM service.

This 99's issues have been getting worst, for ~4 years now. Now becoming so bad, it's dangerous to drive, due to fumes and potential fire hazard.. Getting basics in-line first is very important, or we'll "chase our tails". So often just a series of little things add up to bigger headache over time.. Which may be case here!

Findings:
While inspecting and working on completing below stuff. I found below notable and more:

• Coolant low (1 gal).
• Vacuum leaks.
• K&N filter.
• MAF oily looking.
• Thermostat was missing jiggle valve (just gone, strange!).
• Radiator cap can't hold 5PSI.

Thermostats O-ring installed poorly, which became pinched. Seems whomever worked on thermostat, likely had leak after install. Which would explain why so very over-torqued and damage the 3 nuts were. Apparently they did a lower radiator hose replacement and found pitting on goose neck. Removed, cleaned and installed, at which time, mess up the gasket and over torque to stop leak (bad idea).

I also replaced Fuel Pressure Regulator, as a hunch, more due to age really. Thoughts here is; old FPR allowing to much fuel to return to fuel tank too fast, and reducing fuel pressure in fuel rails. This can cause a lean running condition and increase amount fuel returning to tank, possible making it difficult for EVAP to handle pressure. Just my thoughts, no real evidence of this..

Big thing was coolant very low, IMHO. Overheating or running hot can occur, without much movement of temp gauge on dash or even read low temp (cool running) on gauge. Gauge does not move much as temp swings in most 100 series. But the real problem is when coolant so low, temp sending unit is reading air rather than coolant. The temp sending unit sit high in the engine. So we don't have to be very low to get a false reading.

List or services preformed and parts used:

Inspect, Pull shielding #2, CLN upper engine
Competed​	Parts used.​
Coolant Sys	Found ~ 1 gal low: Drain, clear PS block drain & restore threads. BG flush.​
Heater Tees​	OEM​
N0 1 Heater hose​	OEM​
Thermostat​	OEM​
Thermostat Gasket​	OEM​
Coolant​	2 gal. Toyota LL RED 100 %​
D Water​
BG flush Kit w/ cool​	BG​
Radiator Cap​	OEM​
Inlet housing cap (goose neck)​	1283B to temp repair filling pits​
Nut, inlet housing cap​	Nuts where damaged and very over torqued. O-ring in wrong​
Minor tune
Throttle body CLN​	CRC or BG cleaner​
MAF sensor CLN​	CRC​
Battery post CLN & Grease​	White lithium grease, to stop oxidation.​
Fuel pressure reg​	OEM​
Air filter​	Denso, (had lying around, prefer Toyota)​
Head cover re-torque​	Cover gaskets leaking oil. Bolts loose. This may stop leaks. If not, new head cover and oil tube seals will be needed.​
Propeller shaft & spider lube points
Grease MI tube​	Just some PM​
Oil & Filter
M1 5w-30​	Cust sup​
Drain plug gasket​	OEM​
M1 Filter​	M1 209 is the larger we use​
Vacuum & PCV Repair
Air tube R&R​	OEM Used​
Air pipe/engine cover bolt​	Replaced with used. (Old air pipe glued, may have had leaks and or blockages).
8" vac rear air pipe​	OEM​
VSV to CC vac assemble lines​	OEM​
PCV hose PS OEM​	OEM​
PCV hose DS OEM​	OEM​
PCV grommet​	OEM​
PCV Valve​	CLN​
Cut tip of Idle up control vac hose to air box​	Shop​
Clip double VAC line VSV to CC​	Shop​

After working on basic's:

I took for a short test drive just around town, w/OAT of 95F in the mile high city (Denver). I noticed, via my bluetooth tech stream app. engine temp would rapidly jump to 205f with both A/Cs on sitting at a stop lights, and hold around ~182 to ~192F just driving around w/A/C off. Rapid changes in engine water temp is not normal, nor is reaching 205F. I suspected radiator fin clog, cleaning radiator fins which I find often. I did not get any fuel smell. I did 3 stop and shutting downs opening gas cap. I did not get anymore than the normal very short hiss (<1 sec). No fuel smell at all. Only concern was temperature of coolant behavior.

I was trying to be very minimal on this service, as Gavin did not want anymore done (money spent) until we solve the fuel smell and fuel tank pressure issues. He said he just sell it, if I can't correct the issue. So I never even had front (#1) skid plate off. But I did wash radiator fins from engine side outward, just a little tad. I saw front of #1 skid collecting gunk from radiator washing as I did so. So thought good enough for test drive by Gavin. I should have looked closer or re-test drove first, to check temps!

Running better with reduced instance of fuel issue, but:

Gavin loaded with the family (4 grown-ups), drove up into foothills of Boulder CO. He said it was 100 % better running and no fumes on way up and driving around town. But after returning from a hike up Boulder Canon, they smelt fuel as the walked up to the vehicle. Then while driving further into mountains, fuel smell became overpowering. They turn back to Denver.

Thorough cleaning of radiator fins and now much better:

I had him bring it back over. I need to take a better look at radiator. What I found, was coolant/engine temp was still going up. So pulled #1 skid plate and really clean the radiator. In fact, it was the worst/dirtiest I'd seen. I must have gotten a shove full or more, of bugs, cotton, grass, gunk, etc out of fins

Notice how bank 1 long term fuel trim is 7%. That is a bit high. Long term indicates what the ECU is doing to adjust for short term. So this indicates, bank 1 running lean (HOT). Fuel line run along side Bank 1 CAT..
Just idling before fully cleaning radiator fins (after lite cleaning, no AC), after tune and coolant flush with new thermostat & Cap. Also used BG flush/cool kit.:

After fully cleaning radiator (hours). Notice how temps and fuel trims improved.

I added a can of 44K to fuel tank, the night before my test drive. After which I kicked-up Fuel injectors to max fuel ~24.8% (my new trick), through tech stream. Than idling a few minutes and shutting down, soaking overnight with this rich mixture of 44K now in the fuel system and combustion cambers.

Now I took on 6 hour test drive, into mountains and city streets.
Engine coolant temp stayed between 184 & 189 most of the drive, OAT 75F to 95F. The one exception was after near 6 hours of driving, I ended up in stop and go traffic in the city, with OAT 95F. Here I saw temps up a little higher. Throughout the day, I stop and remove gas cap periodicity, hiss was normal, with exception of end of day. At which time I heard the hiss for a few seconds. No fuel smells at any time!

Now, Gavin has taken on a second test drive, up into mountains. He's happy, all is working great.

I feel we're 98% of the way to correcting the problem. I'd like additional test drive, with full tank of gas while climbing offload to at least tree-line (12,500 above sea leave). That is the acid test here in Colorado. I feel that last gas cap removal test I did in the city, with OAT at 95F, had a little longer hiss than it should. This may be due to hanging up of venting valve (cut off valve perhaps), due to gunk.

Gunk from fuel boiling, over pressuring fuel tank and EVAP:

Cut off valve: I've never look at one, until I saw picture just a few days ago. It made me wonder about gunk causing it to stick.

I say gunk, because I noticed something on this 99's gas tank skid plate. That it was kind of gunky, rather than painted metal or rust. Kind of oily looking. Then I recalled the Unicorn , which had a very badly overheated engine, it blew the head gaskets and cooked the engine. I believe the Unicorn had and overheating issue, due to low coolant from improper burping of coolant system. That issue went on for 20K miles (~1 yr) and kill the engine for good. It also had a palatially clogged radiator (fins) from cotton, grasses and Styrofoam. With the Unicorn, I had noticed a lot of gunk in gas cap area under lid. I remember thinking, how could this area under gas cap cover/lid of body, be so gunky. Was PO putting in some strange fuel or what. In fact, it was in part, why I drained that fuel tank. I now realize it was fuel tank boiling over. Pressure building in tank, due to gasoline being overheated by the hot engine and hot CATs heating the fuel lines. That the fuel as it boils, an fumes blow out gas cap, from high pressure. It leaves behind a gunk. I got further anecdotal evidence of this last weekend, while working on a family from FL 00LX. They'd been traveling here from FL and started having issues with shutting down and EFI fuse. I found the engine was likely overheating due to coolant issues. It's reservoir hose was not straight in the reservoir. It got hung up on the shelve within. This cause radiator to suck air during cool DN cycles. So air bubble get in radiator. Then next cycle reservoir overfill as air displace more coolant, and blows off excesses in reservoir and more air is sucked in radiator. The cycle leads to low coolant level. He was 2 qts low in radiator and 1 qt low in res. I checked gas cap area, and sure enough some gunk on gas door/lid and inside area.

So this same gunk may be getting into cut off valve and VSV valves of EVAP. I need to look closer and get better understanding of the venting and valves of the fuel re-circulation and EVAP and venting. But this sticking may not trip a DTC, and may be effect by filling gas tank and going up rough mount roads. The cut off valve "may" (IDNK), be limiting venting. As we fill tank, than get into shaking/sloshing fuel going up mountain off road passes. It may push up the shut cut off valve, and it may stick up in a near or complet cut off position. Again I do not have a good understand of this cut off valve. This is just a thought that I need to explore. The valve may not have anything to do with venting. It may just function to stop fuel from leave gas tank, in a rollover or too great and angle.

But in at least this 1999 case. I'm sure overheat was the factor the cause the issues of fuel smell and fuel cap pressure (long hiss). That the bank 1 CAT was running very hot, heating fuel lines due to engine overheating. That it is very likely most all excessive fuel pressure issues, without a DTC being set off, is due to engine not running properly. Other cause that may not set off a DTC, could be things like missing heat shield or damaged CAT (fuel soaked over heating of CAT).

Bottom line, 4.7 2UZ are great engines and just keep ticking. But all engine need to be properly tuned.

I hope this thread helps shine a light on this issue. I hope to see more of these cases. I will tackle all the same. By first getting the basic in line.

 

[Mike6158]

I'm going to follow this thread. I think that you've asked very good questions. Doesn't the charcoal canister have a connection to the vacuum system? I don't have my service manual so I can't look at the fuel system diagram. If pressure is building it has to come from somewhere and be the result of something not working correctly. Pressure "could" be heat related but gasoline is a hydrocarbon that is sometimes polluted by alcohol. Natural Gasoline has an RVP specification that it has to meet quoted from here

"Depending on the state and month, gasoline RVP may not exceed 9.0 psi or 7.8 psi (@100 deg F). EPA provides a 1.0 psi RVP allowance for gasoline containing ethanol at 9 to 10 volume percent." It's not PSI though... it's PSIA (absolute pressure takes altitude into account)

In Colorado, PSIG = PSIA - 12.x ish. So to get a 9 psia RVP fluid to be a positive pressure in the tank in Colorado you have to lower the outside pressure (higher altitude) and/or raise the temperature of the fluid.

Circling back to the charcoal canister / vacuum system paragraph, if gasoline condenses in the charcoal canister, @ normal temperature (colder at altitude) and pressure you would have to pull a vacuum on the canister. A leaking vacuum line might prevent that. If the canister is too cold, the vapor pressure of the fluid may be too low and the vacuum system might night be able to cause the fluid to vaporize. Also, if you pull the pressure down the act of vaporizing the fluid makes it cool (latent heat of vaporization). The fluid wants to be at equilibrium.

 

[2001LC]

My thinking is along the lines of vacuum as you. Also pressure that is delivery into tank.

Yes the CC does have vacuum lines coming off it, connected to intake manifold via a VSV on DS and from air pipe (resonator) on PS. This is on the 98-02.

In 03 CC was moved to the rear near spare, from the engine compartment. I'll need to look at the newer 06-07 vvt, but 03-05 for sure has the same vacuum points off DS & PS from intake & pipe. I'm not sure if vacuum pulled from other point also, but can't think of any.

I'm also not sure if this issue spans all years. Perhaps will get some feedback here on what years?

Edited 7/4/20: But before all else, engine basics need addressing.

 

[saucebox]

It definitely happens on a 2003 LX at either high altitude or high OATs (98+ ºF).

I've replaced the charcoal canister in the rear with new OEM (last fall), and gave it a new OEM gas cap as well. Neither have solved the problem—as it's warming up here, the pressure and fumes are back.

 

[ZREM]

Following this thread for sure. I have same issue, usually see symptoms related to heat (90*+outside temp), towing and/or altitude. I have replaced charcoal canister and fuel cap with no positive results. My kids hate the smell, and this issue may be the thing that pushes me to sell the LC if I can't figure it out.

 

[JunkCrzr89]

I'm going to follow this thread. I think that you've asked very good questions. Doesn't the charcoal canister have a connection to the vacuum system? I don't have my service manual so I can't look at the fuel system diagram. If pressure is building it has to come from somewhere and be the result of something not working correctly. Pressure "could" be heat related but gasoline is a hydrocarbon that is sometimes polluted by alcohol. Natural Gasoline has an RVP specification that it has to meet quoted from here

"Depending on the state and month, gasoline RVP may not exceed 9.0 psi or 7.8 psi (@100 deg F). EPA provides a 1.0 psi RVP allowance for gasoline containing ethanol at 9 to 10 volume percent." It's not PSI though... it's PSIA (absolute pressure takes altitude into account)

In Colorado, PSIG = PSIA - 12.x ish. So to get a 9 psia RVP fluid to be a positive pressure in the tank in Colorado you have to lower the outside pressure (higher altitude) and/or raise the temperature of the fluid.

Circling back to the charcoal canister / vacuum system paragraph, if gasoline condenses in the charcoal canister, @ normal temperature (colder at altitude) and pressure you would have to pull a vacuum on the canister. A leaking vacuum line might prevent that. If the canister is too cold, the vapor pressure of the fluid may be too low and the vacuum system might night be able to cause the fluid to vaporize. Also, if you pull the pressure down the act of vaporizing the fluid makes it cool (latent heat of vaporization). The fluid wants to be at equilibrium.

My thinking is along the lines of vacuum as you. Also pressure that is delivery into tank.

Yes the CC does have vacuum lines coming off it, connected to intake manifold via a VSV on DS and from air pipe on PS. This is on the 98-02.

In 03 CC was moved to the rear near spare, from the engine compartment. I'll need to look at the newer 03-07 for sure the same point off DS from intake. I'm not sure if vacuum pulled from another point also.

I'm also not sure if this issue spans all years. Perhaps will get some feed back here on what years?

I agree that this is most likely related to the evap system. Cracked/clogged charcoal canister, VSV stuck/failed, etc. However, any of those issues should throw CEL at some point...hopefully before it goes up in flames. Easy to periodically check function of everything in evap system with Techstream.

 

[Mike6158]

My thinking is along the lines of vacuum as you. Also pressure that is delivery into tank.

Yes the CC does have vacuum lines coming off it, connected to intake manifold via a VSV on DS and from air pipe on PS. This is on the 98-02.

In 03 CC was moved to the rear near spare, from the engine compartment. I'll need to look at the newer 06-07 vvt, but 03-05 for sure the same points off DS & PS from intake & pipe. I'm not sure if vacuum pulled from another point also.

I'm also not sure if this issue spans all years. Perhaps will get some feed back here on what years?

2000 LC. It's a problem at higher (than the gulf coast of TX) altitude and in the desert heat of Big Bend. If there was a way to circulate hot coolant around the charcoal canister that might help. It seems like Toyota would have addressed it

 

[J1000]

I'm about to replace all of the lines in my entire fuel system and gas tank probably with quality Gates not OEM. Even the gas fill neck connection. On my truck I have the opposite problem, no pressure build up in the tank at all but fumes around the rear end at times. The earlier trucks built up crazy pressure, the newer trucks just leak it out. Fuel temp gets well over 110F on an average 70-80F day, and if it's hotter then 120+F fuel temperature is reached. Since no pressure build up this means the fuel boils.

I have followed the FSM procedure for pressure testing the fuel vapor system and I have multiple leaks from nearly all hose connections on or around the gas tank.

I've already done shielding of the fuel lines the next step after I replace all of the fuel vapor lines is adding a fuel cooler radiator and fan with a 100F thermostat.

Fuel cooler: Amazon.com: Dorman 918-337 Fuel Cooler for Select Chevrolet/GMC Models: Automotive
100F thermostatic switch: Amazon.com: Midwest Hearth Thermal Fan Switch for Fireplace Blower (115 Degree ON, 90 Degree OFF): Home Improvement

My two point plan is to try and further reduce fuel temperature and secondly stop all vapor leaks.

 

[BadReligion]

It definitely happens on a 2003 LX at either high altitude or high OATs (98+ ºF).

I've replaced the charcoal canister in the rear with new OEM (last fall), and gave it a new OEM gas cap as well. Neither have solved the problem—as it's warming up here, the pressure and fumes are back.

That's not encouraging. My 03 is doing the same and before putting in a LRA aux tank, I was planning on replacing the charcoal canister. At like $400 I was hoping this would take care of the problem. No fumes in the cabin but lots of vapor release when opening the fuel cap. Not as bad as my 80 which will actually spray fuel.

I also have issues mostly in the summer and after extended or high elevation driving. I'm sure the 10% ethanol blends do not help. Heat shielding around the fuel lines is not a bad idea. Definitely following this thread.

 

[87warrior]

I continue to have excessive fuel pressure in the gas tank, even here in Kansas. 1999LC @ 336k miles. Had the issue when I bought it @ 245k miles. The only time I had a violent fuel boil and gas spew past a good gas cap was on Fathers Day in Colorado a few years ago, at 90° and 10,000' climbing Hayden Pass.

I am convinced the issue is due to excessive heat around the fuel tank due to the exhaust routing. At a low speed there is no where for the excessive heat to go, so it boils the gas in the fuel tank.

In an effort to combat the problem I have replaced the following parts with NEW Toyota parts:

• Charcoal Canister
  • Purge valve
  • Vapor pressure sensor
• Gas Cap
• Fuel tank vent
  • Fuel tank vent tube assembly
• Fuel pump gasket

And non-Toyota parts I have used:

• Denso Fuel pump
• Bosal Muffler

I now no longer smell raw fuel vapor. In my case, I believe the fuel vapor smell was coming from the line connecting the charcoal canister to the frame rail. I assume this is an "overflow" vapor line for the canister. I do get a huge blast of fuel vapor when I remove the gas cap to fill up. I've noticed no difference in fuel vapor pressure between starting with a "full" tank or a "3/4" tank. Interestingly enough I have not noticed a difference between the stock fuel tank and the LRA 40 gallon. The result is always the same. I HAVE noticed a drop in fuel vapor pressure by using Ethanol Free gas, but not eliminated.

 

[saucebox]

That's not encouraging. My 03 is doing the same and before putting in a LRA aux tank, I was planning on replacing the charcoal canister. At like $400 I was hoping this would take care of the problem. No fumes in the cabin but lots of vapor release when opening the fuel cap. Not as bad as my 80 which will actually spray fuel.

I also have issues mostly in the summer and after extended or high elevation driving. I'm sure the 10% ethanol blends do not help. Heat shielding around the fuel lines is not a bad idea. Definitely following this thread.

Shielding is next, fingers crossed. I hate the idea of underfilling by 1/4 tank as a fix (but that does work).

 

[katit]

• Purge valve
• Vapor pressure sensor

Just speculating here. Reading all the posts - it's got to be an issue with circuitry and not so much with hardware.

Sensor should "sense" pressure.
Then valve should purge it.

Is there "brain" between those? To read sensor and command valve?

Is there tests in computer diagnostics to read pressure and command valve?

It is very simple system. I bet on valve not opening for some reason.

 

[ikarus]

Might be good to check with the 80 series guys as well. A couple years ago I was on a mountain pass at 10K feet when the gas pressure/boiling happened to me and a few 80s. One of the guys shurgged and said it had been going on in his cruiser for 10 years - and he'd rather just have it vent vs building pressure in the tank and having the tank rupture or explode.

 

[ticoman]

I take it this is only an issue in the UZ models and not the HD models. I have an Diesel 80 and 100 and have never experienced this. Nor have I heard of it.

 

[abuck99]

Mainly North America issue with EVAP emission controls and gasoline engines.

 

[Jfoofighter16]

So I dont know how to link my other previous posts from my phone here, but I have this problem, just had it happen today, notnboiling but if I had driven another hour I bet it would have been, definitely venting fumes/pressure from brand new gas cap, almost like a dull farting as it pushes against the rubber/silicone cap gasket. I have 03 as well.

I think for some reason some of our engines are running hot to where the return fuel line gets too hot. I did some random googling for fuel boiling/hot fuel issues on any cars and this seems to be the most common culprit. So now the question to me is how do we keep our fuel cool (seems to be that old carburated engines this was common place to rig up some sort of ice box situation to avoid vapor lock/fuel heating).

I also came across this Advance Auto Parts - Down for Maintenance
I know this could the fuel prior to entry but in theory it would keep engine cooler from the get go.

The part that bugs me most is I ran me obd2 app and while my old 03 combined with whatever app/obd2 product I'm using (bluedriver) same me engine coolant temp never even got over 195 the whole trip today. But when I got home I opened hood and I could see how return fuel would be boiling hot with how freaking hot the area of engine/bay was where the fuel returned are. Also if you read my old posts, yes I have replaced the ECT with OEM part so I dont think I'm getting false reading on engine temp. Also toyo dealer just rechecked evap system this last week and reported no issues

Not sure if anyone thinks this product I found would work or of someone with the wherewithal to install (as I do not have that) on my vehicle as an experiment would be fine with me. While I love my rig and have built it up and spent way too muchl$ to try and fix this problem, since I have kids I cant just shrug the problem off and vent the gas or other bandaids other may be comfortable with.

While my long list of things I have done seems to have helped delay the problem, it is still not gone. Now with building up my rig, more weight and having a trailer, it seems easier to cause this problem.

My only other thought is polling how many ppl have regeared there front/rear riffs versus not and if the regeared rigs experience this problem less. Inknow it's a long shot but if we are running bigger tires/lift/armor and invariably making engine work harder there will be more stress/heat. If regearing eases some of this stress, would engine not run cooler in theory?

At this point I'm just desperate probably (and despite the problem still down to build up me rig more by regearing lol!)

Definitely following this but I dont know what else to do/say this problem saddens me because I have no other problems with my rig at all and this is just too big/risky of a problem for me and makes me feel like this is going to be what makes me get rid of rig eventually.

 

[saucebox]

My only other thought is polling how many ppl have regeared there front/rear riffs versus not and if the regeared rigs experience this problem less. Inknow it's a long shot but if we are running bigger tires/lift/armor and invariably making engine work harder there will be more stress/heat. If regearing eases some of this stress, would engine not run cooler in theory?

At this point I'm just desperate probably (and despite the problem still down to build up me rig more by regearing lol!)

Definitely following this but I dont know what else to do/say this problem saddens me because I have no other problems with my rig at all and this is just too big/risky of a problem for me and makes me feel like this is going to be what makes me get rid of rig eventually.

Also regeared, though barely moved up to 4.30 (added a locking third to the rear, matched at the front). Very heavy at 7500lbs. No change, but then I'm only running 100-200rpm less than before.

 

[ikarus]

So I dont know how to link my other previous posts from my phone here, but I have this problem, just had it happen today, notnboiling but if I had driven another hour I bet it would have been, definitely venting fumes/pressure from brand new gas cap, almost like a dull farting as it pushes against the rubber/silicone cap gasket. I have 03 as well.

I think for some reason some of our engines are running hot to where the return fuel line gets too hot. I did some random googling for fuel boiling/hot fuel issues on any cars and this seems to be the most common culprit. So now the question to me is how do we keep our fuel cool (seems to be that old carburated engines this was common place to rig up some sort of ice box situation to avoid vapor lock/fuel heating).

I also came across this Advance Auto Parts - Down for Maintenance
I know this could the fuel prior to entry but in theory it would keep engine cooler from the get go.

The part that bugs me most is I ran me obd2 app and while my old 03 combined with whatever app/obd2 product I'm using (bluedriver) same me engine coolant temp never even got over 195 the whole trip today. But when I got home I opened hood and I could see how return fuel would be boiling hot with how freaking hot the area of engine/bay was where the fuel returned are. Also if you read my old posts, yes I have replaced the ECT with OEM part so I dont think I'm getting false reading on engine temp. Also toyo dealer just rechecked evap system this last week and reported no issues

Not sure if anyone thinks this product I found would work or of someone with the wherewithal to install (as I do not have that) on my vehicle as an experiment would be fine with me. While I love my rig and have built it up and spent way too muchl$ to try and fix this problem, since I have kids I cant just shrug the problem off and vent the gas or other bandaids other may be comfortable with.

While my long list of things I have done seems to have helped delay the problem, it is still not gone. Now with building up my rig, more weight and having a trailer, it seems easier to cause this problem.

My only other thought is polling how many ppl have regeared there front/rear riffs versus not and if the regeared rigs experience this problem less. Inknow it's a long shot but if we are running bigger tires/lift/armor and invariably making engine work harder there will be more stress/heat. If regearing eases some of this stress, would engine not run cooler in theory?

At this point I'm just desperate probably (and despite the problem still down to build up me rig more by regearing lol!)

Definitely following this but I dont know what else to do/say this problem saddens me because I have no other problems with my rig at all and this is just too big/risky of a problem for me and makes me feel like this is going to be what makes me get rid of rig eventually.

That's interesting, hadn't thought of that. The only data points I have are these:

May 2018 (referenced earlier in the thread) - Henry Mountains, UT. Stock gears with 34" tires. 6500-7000 lbs. Drove from 6,000 feet to 10,500 feet in a couple hours. Got to the top of the pass and had fuel puking out the filler tube - ate my paint and was hissing for a while. Probably 1/2-3/4 of a tank.

May 2020 - Deep Creek Mountains, UT. 4.88 gears with 35" tires. 6500-7000 lbs. Drove from 5,000 feet to 9,000 feet in a few hours. Got to the top with no problems, but I could smell gas venting from the charcoal canister under the hood. Again probably 1/2-3/4 of a tank.

Don't know if that helps but if it helps it sell gears and lockers to you and/or your accountant, hell yeah brother do it

 

[95Fantasma80]

It definitely happens on a 2003 LX at either high altitude or high OATs (98+ ºF).

I've replaced the charcoal canister in the rear with new OEM (last fall), and gave it a new OEM gas cap as well. Neither have solved the problem—as it's warming up here, the pressure and fumes are back.

add me to the list of smelling gas in cabin sometimes, happens in 🏜 and when climbing mountains at lower speeds. Might also have close to full tank or 75% or more.

I also get a code once or twice a year, which people say it's either a new charcoal canister i need or a gas cap... I've always just reset it and made sure the gas cap is tight and doesn't come back...

I also sometimes notice when i take off gas cap it vents out like if there was a lot of pressure inside, that might be contributing.