Gas tank building excessive pressure & fuel smell. Dangerous for sure! Why does this happen? (11 Viewers)

[2001LC]

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In hindsight what I originally chalked up to bad gas was not, and is obviously this. I've read through this whole thread since we're now residents of Telluride sharing time between there and Atlanta. The LC will be primarily residing in CO so I'm paying close attention to this thread and will contribute as much as I can.

06 LC "Lucy", bought 2 years ago with 145k. Slee step sliders and 33" tires. Otherwise stock. Purchased in Seattle in 2020 and drove to Atlanta.
When traversing Vail Pass we pulled off at the rest stop there and upon cranking up again had vapor lock. Took about 15min then fired right up and never gave another issue since then. I can't say if there was gas smell but certainly no fuel gush. OAT was 100+ before we climbed to the pass, so a little cooler at the stop.

in GA my ECT is 192-196 in OAT 90+ which seems to now be the accepted standard for the later models. I do plan to clean out the radiators this weekend and see if this lowers any as @2001LC has successfully done but won't be concerned if it stays in that range. It'll be interesting to see what happens when Lucy gets to CO and experiences these different scenarios.

One thing I have not seen mentioned on topic with temperature is relative humidity. Not sure how much of an impact that would have on the fuel but in theory the drier climate (CO) will allow for much quicker evaporation than humid heat (GA). And if we're talking about water vapor in the gas having an impact, that has to play a part, right?

I have my scanner now set up to read ECT, FT, IAT, MPG, RPM, AT1&2, Evap VSV

Typically a fuel boiling event, we do smell fuel. A rig boiling fuel will have muck in gas cap area 9 out of 10 times.

Another issue we have in 06-07 100 series, is a bad fuel pump. When they get hot, by running in high speed. Which ascending hill we run in high RPM, which kicks fuel pump into high speed. On hot days, these fuel pumps build excessive resistance. It's very often thought of as vapor lock. Let it rest and cool, it will start right back up. If using a codes reader during event, we very often get BK 1 & 2 lean codes.

Trying running in high RPM for 10 minutes or so on a hot day, on hot blacktop, after driving around for 30 minutes. Then drop RPM suddenly to an idle. See if it dies.

 

[gatormark91]

Subscribed.
In hindsight what I originally chalked up to bad gas was not, and is obviously this. I've read through this whole thread since we're now residents of Telluride sharing time between there and Atlanta. The LC will be primarily residing in CO so I'm paying close attention to this thread and will contribute as much as I can.

06 LC "Lucy", bought 2 years ago with 145k. Slee step sliders and 33" tires. Otherwise stock. Purchased in Seattle in 2020 and drove to Atlanta.
When traversing Vail Pass we pulled off at the rest stop there and upon cranking up again had vapor lock. Took about 15min then fired right up and never gave another issue since then. I can't say if there was gas smell but certainly no fuel gush. OAT was 100+ before we climbed to the pass, so a little cooler at the stop.

in GA my ECT is 192-196 in OAT 90+ which seems to now be the accepted standard for the later models. I do plan to clean out the radiators this weekend and see if this lowers any as @2001LC has successfully done but won't be concerned if it stays in that range. It'll be interesting to see what happens when Lucy gets to CO and experiences these different scenarios.

One thing I have not seen mentioned on topic with temperature is relative humidity. Not sure how much of an impact that would have on the fuel but in theory the drier climate (CO) will allow for much quicker evaporation than humid heat (GA). And if we're talking about water vapor in the gas having an impact, that has to play a part, right?

I have my scanner now set up to read ECT, FT, IAT, MPG, RPM, AT1&2, Evap VSV

Evap VSV will not always report a bad VSV.

 

[daohaus]

Got my roll of reflective tubing great shield. Going to wrap the fuel lines next to the exhaust to see if it helps with the pressure build up I'm getting when I open my gas cap

 

[DTC72]

Got my roll of reflective tubing great shield. Going to wrap the fuel lines next to the exhaust to see if it helps with the pressure build up I'm getting when I open my gas cap
View attachment 3062410

Get some adhesive backed heat shield to put on the corners of the gas tank by the cat and exhaust also.

 

[daohaus]

Get some adhesive backed heat shield to put on the corners of the gas tank by the cat and exhaust also.

I'll do that as well thanks!

 

[abuck99]

Got my roll of reflective tubing great shield. Going to wrap the fuel lines next to the exhaust to see if it helps with the pressure build up I'm getting when I open my gas cap
View attachment 3062410

I purchased the same roll of heat reflective wrap- NOTE- the thread stitching the velcro on will unravel in 1 pull so be carfefull when you go to trim lengths of it- use some RTV to glue down the threads and Velcro on the ends- this will save it from coming apart.

 

[daohaus]

I purchased the same roll of heat reflective wrap- NOTE- the thread stitching the velcro on will unravel in 1 pull so be carfefull when you go to trim lengths of it- use some RTV to glue down the threads and Velcro on the ends- this will save it from coming apart.

And I appreciate this tip thank you!!!

 

[daohaus]

Think I got the critical areas. I purchased this roll of reflective velcro wrap, i used two cut to the same length to get it wrapped around the 3 lines. Worked out pretty good. The adhesive backed heat shielding was pretty good to work with as well. This is a 2 job if that.

 

[Berkut10r]

I know that this suggestion maybe too far out but has anyone concerned Jet-Hot treatment for the exhaust components?

 

[AlamoCruiser]

Lastly, I used some embossed heatshield material to shield the front crossover y-pipe from the front of the fuel tank: Amazon.com: Design Engineering 050503-16 Floor and Tunnel Shield: Automotive This stuff is really lightweight and easy to bend and and cut and work with but also extremely effective at blocking radiant heat.

I don't know if this is a dumb question, but would exhaust wrap accomplish the same thing? I'm in the process of performing these steps to mitigate my fuel vapor issues at elevation, and this thought popped into my head. I really appreciate the extent of your testing and data gathering, it's making this process easier than I initially expected, and I know I'm not the only one

 

[Brandon Ryder]

I don't know if this is a dumb question, but would exhaust wrap accomplish the same thing? I'm in the process of performing these steps to mitigate my fuel vapor issues at elevation, and this thought popped into my head. I really appreciate the extent of your testing and data gathering, it's making this process easier than I initially expected, and I know I'm not the only one

I asked the same question at one time and it was brought to my attention that those wraps can accelerate rust if the exhaust system. So if you live in an environment that has wet roads or road salts, the wrap can hold onto the moisture and can't really be washed off.

 

[J1000]

Wrapping is a huge pain in the butt also so you'd definitely have to do it with the exhaust off the car. I think you would still need a heat shield, wrap will reduce the heat it puts off but not eliminate it. If you get the exhaust ceramic coated that would be the best option but also expensive.

 

[AlamoCruiser]

Thanks for the responses. I went ahead and ordered stuff for Steps 1, 2, and (partially) 3 as noted by J1000 and should have it arriving this week for install. I'm looking forward to (hopefully) not worrying about the fuel vapor issue anymore as it really concerns my wife when we're on the trail

 

[Joe422]

Yea, In Big bear around 6-7K elevation, long slow drive up the trail... my fuel got hot, pressurized and started smelling outside.
I pulled the fuel cap off and the lower atmospheric pressure from the altitude made the fuel boil soon after.
I let it sit venting for 10-15 mins, and everything was fine after that... but everything was hot... the fuel filler tube, etc.

The interesting note for me was when my wife complained that the floor (passenger front) was hot, as well as the front passenger seat frame. I was running AC on the trip, cus it was in the low 90's outside, so no need for the seat to be hot.

Looked under the LX, and the cats are right under the front, passenger seat. (Magnaflow direct fit cats).
Made me realize its not just gonna be shielding the fuel lines, but I wanted to shield the Cats themselves too
(Magnaflow cats have no heat shield like OE does).

Im going to try this route... already ordered all the materials (Heatshield Products... 1/2" thick) to cover the cats, and some of the pipes.
Will wrap the fuel lines too w/ the Velcro style wraps (DEI) as well.

 

[daohaus]

Happy to report after installing the heat wrap around the fuel lines as well as shielding portions of the gas tank near the exhaust pipe I have not witnessed any pressure when I crack open the fuel cap to pump gas into the LX

 

[bajaguy949]

I just came back from Coyote Flats this weekend and had extreme venting occur and gas spilling out. As other have reported having issues on this trail I tried to prep and do some of the suggested remedies. I wrapped the fuel lines with reflective velcro wrap and stuck adhesive heat shield on the exposed corner of the fuel tank.

Tank began to start venting early on in the trail as we climbed at the start (steep) 4k to 10k feet. The temp was 95 degrees at the start with a full tank. I stopped for 15 minutes to let the 100 cool down with no success when I noticed the smell of gas. Venting would not stop and I eventually made the decision to keep going.

We got up to the flats and ran some other trails and got above 11K with the tank continuing to vent. When we got to camp a few hours later the venting had finally subsided.


Attached are pictures if anyone has any suggestions (wrap fuel lines higher up? Heat shield on Cat and Fuel Tank?). I installed a new OEM radiator about 6K miles ago and monitored temps which never fluctuated so no heating issues.

Vehicle is a 99 LX with 193K miles.

 

[DTC72]

I wrapped fuel lines all the way into the engine bay to engine and up to the fuel filter. Heat shield only on two sides of gas tank. 2006 LC. I just got back from Silverton, CO running peaks to 12k and 13k feet. No vapor lock or fuel boil at all.

 

[harshjay]

Adding to this thread just to share my recent experience and provide a bump in case anyone has managed to identify a more definitive remediation action or sequence of actions...

I was in the deep backcountry of the Needles district in Canyonlands National Park yesterday tackling Elephant Hill trail with some buddies in jeeps. Area elevation was ~5,000 feet and afternoon temperatures were approximately 103 degrees Fahrenheit as we worked our way through a couple of hours of challenging obstacles, inclines, and deep sand on portions of the trail. My well maintained 2006 LX470 with 225k was already showing a set of lights due to an O2 sensor that lit up the day before our Moab trip began, so I can't speak to any visual indicators that may have accompanied the behavior during the trail run.

We stopped for about five minutes and I turned my engine off. I could smell fuel, but had experienced this same behavior on previous trails upwards of 10,000' elevation in Colorado, so I wasn't immediately concerned with the whiff of fuel or the slight fuel seepage showing from under the fuel door. See photo indicating this slight seepage where the red dust adhered to the rear quarter panel.
View attachment 2349290
I restarted the vehicle and it idled rough for about 30-seconds as I began driving forward in the sandy trail. I stopped the truck and the engine died. Multiple restart attempts failed in the next 5 minutes. Tank was 3/4 full of high octane gas and engine temp and oil gauges showed normal operating range. Fearing a long, complicated extraction effort, we immediately began towing the vehicle out in the easiest direction but encountered a boulder-strewn obstacle within about five minutes. We got out to scout a path and make a plan for the tow vehicle and my LX470 sat under shade of a nearby rock for about 15 minutes. Before we attempted the tow through the obstacle ahead, I gave it one more try & she started up with no rough idle. We quickly unhooked and I drove through the obstacle and then out the next 30+ miles of mild trail and another big obstacle called "Bobby's Hole" with no issues other than exhaust that smelled very rich.

I plan to replace the fuel filter with an OEM and then consider a heat shield between the exhaust & fuel supply lines, but would love to hear any first-person accounts from folks who've had similar experiences and found one or more corrective actions to successfully remediate the behavior. I was dismissive in the cool mountain air of Colorado when it occurred, but when the engine wouldn't start in the deep backcountry of Utah with almost no one around for hours, it was unnerving and I'd like to prevent it from recurring.

We just went through the same exact area, and did a mountain climb outside of Logan the day before. I have had zero fuel pressure / vapor issues up here in Canada (doing big elevation changes up here as well, but not as hot). I got the fuel seepage at Logan, where we went from 3600 ft to 9700 ft, enough to melt my paint within the fuel filler recess. After this, I would stop and vent the cap every few hours. After getting back around Montana....zero fuel vapor issues, still was doing good elevation changes as well. I think this is definitely a heat related + atmospheric pressure problem. Our truck has 100k miles, and is mint. New Charcoal can as well.

 

[harshjay]

I dont have it at all on a '99, regardless of elevation, fuel, load, etc.

At 140k a fuel vapor release valve was replaced which is what I believe causes this. Will try to find the receipt.

186k now. Routinely change from 5k elevation to over 10.5. Several times a year we peak out at around 12k.

what part is a "fuel vapor release valve"... not sure what piece / where that piece exists

 

[harshjay]

And this thread and specific post on Yota Tech explains Toyota's "intrusive" type EVAP system very well ( the best explained step by step diagnosis process I've read yet). This is related to EVAP systems where CC is located above spare tire. Also this requires scan tool or Techstream.

P0446 code - what have you replaced to fix? - YotaTech Forums

95.5-2004 Tacomas & 96-2002 4Runners - P0446 code - what have you replaced to fix? - A few weeks ago, the check engine, VSC OFF and TRAC warning lights came on. In 8-1/2 years and 184,000 miles, I've never had a CE light come on. So I swung by Advance Auto, borrowed their reader and found that...

www.yotatech.com

Basic operation Explained:
"EVAP DESCRIPTION AND OPERATION

Pressure in Tank
As the pressure in the tank builds, it will unseat the tank valve assembly, travel through the charcoal canister, and exit through the fresh air drain.

Vacuum in Tank
As pressure drops in the tank, fresh air comes through the Canister Control VSV, through the air valve, through the canister, through the vacuum check valve, and into the tank through a rollover valve.

Secondary Vacuum Release
The secondary vacuum release is the one way check valve in the gas cap.

Refueling
While refueling, high pressure in the tank forces fumes through the rollover valve, out through the On-Board Refueling Vapor Recovery Valve, through the charcoal canister, and out the fresh air valve.

Purge Mode
While purging, when the EVAP VSV is turned on, it draws air in through the Canister Closed Valve, through the air inlet valve, charcoal canister, and EVAP VSV and into the engine so the hydrocarbons stored in the canister can be burned."

so, if this is all happens as above...why the hell does my gas cap eject as I open it?.... is the gas cap the 'fresh air valve' in the toyota system?