Gas tank building excessive pressure & fuel smell. Dangerous for sure! Why does this happen? (9 Viewers)

[Sykoslug]

Following-
Just acquired an 03, have been noticing this issue of fuel smell coming from the DS area around the gas fill area. It's hard to pinpoint most times but certainly in this quadrant. Was wheeling a pretty steep slick rock climb and noticed fuel had escaped the filler and leaked down the fender below the fuel door... Paint isn't happy.

Drove 45mins from 2500ft to 8000ft with 3/4 tank in 108Fdeg weather last night and the fuel smell was present and wafting from the truck for a good 30 mins.

I was hoping this was a simple issue/fix but it appears more complex.

I was considering upgrading to the 40 gal LRA tank and having all the lines replaced.... This problem makes me want to do that even sooner if it will fix the issue.

Has anyone had success with the LRA tank and new lines? Or is this just the fuel getting too hot and the venting system failing?

I'm going to learn how to read my computer with tech stream and see if there's anything there too.

 

[abuck99]

I’ve been thinking about this for a couple of years trying to make sense of it. Here’s my theory on the issue: This condition is less likely due to a singular problem, more likely points to a combination of factors that lead to excess vapor pressure, and collectively contributes to the EVAP system not being able to keep up with and properly manage excess vapor pressure. Let me qualify that I am no expert in thermodynamics. I think the combination of some or all of these various factors impact the fuel vapor issue.

Vehicle Age: Let's be honest, even well maintained 15-20+ year vehicle platforms are not going to be in optimal mechanical condition which contributes to this problem. Further I think when you operate off road, at high altitude, in summer climate; you have to take this into account and ensure you have good mechanical service awareness of your truck and make the appropriate adjustments to mitigate this issue. Below is a compilation of my thoughts on what to be aware of, and where to look for potential issues.

Fuel: Regional blend differences, tank level, fuel quality (adds or lack there of), octane rating, seasonal blend vs summer blend, ethanol content, butane content: more on that below. Note: Fuel blends are different between many different metro markets across the US based on regional pollution requirements which might help explain why this seems more random to those that do and those that dont experience this issue.

Altitude: Higher altitude contributes to increased vapor pressure

High ambient air temps 85~90f+

Excess engine/under hood temps and radiant heat increasing fuel temperature due to:
a.) poorly maintained cooling system: (dirt and debris in radiator, poorly functioning fan clutch, non functioning radiator cap, failing thermostat, low coolant);
b.) lean condition: ( vacuum leaks, exhaust leaks, clogged cats etc)
c.) failing fuel pump: overheating fuel via cavitation, running fuel on low frequently
d.) failing or failed fuel pump resistor: unable to compensate fuel pump speed and over heating fuel
e.) failing or failed fuel pressure regulator: unable to process return fuel flow adequately

Poorly functioning EVAP System
a.) saturated charcoal canister
b.) poorly functioning switching valves/solenoids
c.) partially clogged pressure switching valve
d.) loose fitting or cracked vacuum lines
e.) partially clogged fuel cut off valve
f.) Pinched or kinked vacuum hose

Off Camber Driving at Altitude with 3/4 to full fuel tank in hot weather: my thought that running off camber at various angles, sloshing gas, warm conditions where fuel and vapors expand fuel inside tank the EVAP line gets fuel or condensation in it and cannot process vapor effectively.

FUEL (dynamics) as a key contributor:
I’ve “plagiarized “ some content from various places to articulate my theory:

Region, seasonality of fuel, climate combined with altitude play a big factor in this vapor pressure issue. This doesn't explain away occurrences in late summer but in later spring/early in summer ( June 1) especially with transition from winter blended fuel to summer blended fuels. Especially in 2020 with substantially less fuel sold due to Covid this spring, the transition from winter to summer blend at the pump may be slow due to turnover at both gas stations and in supplier inventory.

What is winter vs summer blend: “Winter blended fuel contains higher concentrations of Butane which is highly volatile- and vaporizes at lower temperatures, in warm conditions it will cause fuel to boil at lower ambient temperatures .”

Consider FUEL VOLATILITY. “The ease with which gasoline vaporizes is called volatility. High volatility gasoline vaporizes very quickly. A low volatility gasoline vaporizes very slowly. Higher octane fuel has lower volatility, and lower octane fuel has higher volatility.”

“Gasoline is composed of a variety of ingredients that evaporate at different temperatures. The faster vaporizing components evaporate at lower temperatures then the slower vaporizing components. Established standards for gasoline volatility (ability to vaporize). “

"Gasoline with lower evaporation temperatures (more highly volatile) starts easier, warms up better and contribute less to deposits but would have more fuel losses and would be more likely to vapor lock. If the gasoline has too low a boiling temperature it may boil in fuel pumps, fuel lines or in carburetors at high operating temperatures. The vapor causes a decrease in fuel flow to the engine resulting in loss of power, rough engine operation or complete shut down of the engine”.

“Gasoline with higher evaporation temperatures (decreased volatility) wouldn’t have the losses or vapor lock problems but would start harder and not warm up as easily with increased deposits and dilution of engine oil. Exhaust emissions could also increase. If the gasoline doesn’t vaporize sufficiently it will be hard to start a cold engine, cause poor warm up and acceleration, and unequal fuel distribution to the cylinders. To minimize the effects of these driving conditions gasoline specifications change from season to season and take into account geographic considerations. To minimize the effects of volatility on the formation of smog there are further limitations during the summer months.”

“A key aspect of gasoline stability is vapor pressure. This is determined by how much pressure builds up inside a sealed fuel container when the fuel is heated to 100°F. A higher vapor pressure suggests a higher concentration of low boiling point hydrocarbons that vaporize under 100°F. Pump fuels with high (12 pounds/square inch, psi) vapor pressures are used in cold weather to prevent engine starting issues due to low temperatures. Pump fuels are limited to 7.8-9psi maximum in warm weather depending on county and state (www.epa.gov). If stored in a vapor tight container the vapor pressure can be maintained for long periods of time. Fuel exposed to the atmosphere can lose light components within a couple of days. Over time as vapor pressure decreases the fuel can become stale. Stale fuel doesn’t evaporate as easily and can cause rough engine idle and hard starting. Butane is a volatile gasoline component used to tailor vapor pressure in accordance with seasonal needs. Cold weather fuel has higher concentrations of butane. Butane has a high blending octane value which helps manufacturers hit their octane targets. The main downfall of butane is that it boils at 32°F. If the fuel tank is vented to atmosphere the butane can start to evaporate out unless the daily temperatures are below freezing. This makes cold weather fuel more susceptible to vapor pressure loss and octane decreases.”

“The higher the temperature, the higher the altitude, the more likely it is that Gasoline vapors build, This tendency is higher in hotter climate and in higher altitude. Ethanol blending affects the vapor pressure. Adding 10% of Ethanol to Gasoline – as is currently done in the USA - drastically reduces the V/L ratio temperature. Therefore a critical vapor liquid ratio, which can cause vapor lock, will be reached at lower temperatures with Gasoline-Ethanol blends than with regular Gasoline “

“Winter specification fuel will not perform well during the summer months and visa verse it is important to ensure adequate inventory turnover to avoid non-compliant situations as the seasonal requirements change.”


Take what you will from my thoughts on this- or add to it. I believe that a properly maintained engine and properly functioning EVAP system should be able to handle the majority of user conditions for city and highway general offroad use driving from sea level to 10,000+ feet anywhere in the country. We know Ethanol attracts moisture, one theory I have is that as fuel in tank heats up and expands, warm moist vapor and condensation propagates and collects at the top of the tank where the cut off valve is and where the outbound evap line from tank to charcoal canister runs- I think condensation and or sloshing fuel when running trail gets into this line making it difficult for vapor to pass, and what does pass moisture saturates the charcoal in the canister making it difficult for the canister process vapor and keep up.. I have experienced some of these issues at 1,000 feet and 12,000. I noticed as I vented the gas cap very warm and moist vapor came out of the tank- for more than a minute. Since then I’ve made substantial improvements/updates to my cooling system, fuel system and engine so I will report back after my high country trip next month to say if any of it helped and if my theory holds any water.

If you want to test your EVAP system there is a very detailed procedure listed in the Emission Control section of the FSM. (attached)

 

[DTC72]

Vapor lock has happened to my 2006 LC100 4 times over the last 5 years. I’ve replaced a bunch of stuff. Also, I get the heavy fuel smell quite often in the summer here in Las Vegas. This weekend I took a heavily loaded trip to Lake Mead at 102+ and monitored my Absolute Evap System Vapor Pressure readings using my BlueDriver OBD2 and app. I had no gas smell or vapor lock this weekend. My question is does anyone know what the normal range for the Absolute Evap System Vapor Pressure is in inH2O? Mine ranged from 348.07 to 358.41 I just have no idea what is high or normal.

 

[abuck99]

Vapor lock has happened to my 2006 LC100 4 times over the last 5 years. I’ve replaced a bunch of stuff. Also, I get the heavy fuel smell quite often in the summer here in Las Vegas. This weekend I took a heavily loaded trip to Lake Mead at 102+ and monitored my Absolute Evap System Vapor Pressure readings using my BlueDriver OBD2 and app. I had no gas smell or vapor lock this weekend. My question is does anyone know what the normal range for the Absolute Evap System Vapor Pressure is in inH2O? Mine ranged from 348.07 to 358.41 I just have no idea what is high or normal.

The only output I can find related is the value the ECM provides in relation to the specified kPa range in the FSM ( not necessarily the psi, inHg, mmHg? parameters provided BlueDriver). Techstream can read this data, not sure how to get that in BlueDriver

 

[LonghornMudder]

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.

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.

 

[LonghornMudder]

<deleting duplicate post that resulted from poor wi-fi connection>

 

[saucebox]

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.

Replacing the canister helped mine out some...but I still get vapor out of the rear canister at elevation + heat. The canister did help—daily driving at 4500-5500ft is totally normal now except when temps hit triple digits, and then I get the stink. I haven't had it completely boil out of the tank since replacing the canister.

I've also got a new-ish gas cap and a new fuel filter (everything replaced last fall). I've never had vapor lock, but I'd look to the fuel pump at that mileage. I have yet to get around to creating a shield, but one is definitely on the list.

I think I'd start working my way up from the cheapest solutions. Replace the filter, the gas cap, and add a heat shield. Troubleshoot further if problems persist. Or in other words, don't immediately jump to throwing $300+ at a charcoal canister that likely won't totally solve it anyway. Like I did.

I think @abuck99 is on the right track—it's probably not a single component, but a combination of things.

 

[abuck99]

Vapor lock- possibly fuel pump cut off due to excess heat. I think fuel slosh makes this worse.

Curious
Is fuel pump original?
Fuel pressure regulator original?
Radiator clear of dust & debris?
O2 sensor indicating possible lean condition- & running hot


Before throwing any $$ at possibe corrective measures you’ll want to plug in with TS and check for any DTC since engine cut off.

IMO the only way to know for sure what the cause may be is to go step by step through the diagnostic procedure for the EVAP system- its friggin 20+ pages in the DI section of FSM starting around DI-222 that will walk you through trouble symptoms and possible causes tests for each component. Techstream would be helpful to you for this set of tests.

Until you isolate the issue and correct ( if you can correct), if on the trail and its a short stop, its better to leave the truck running as this keeps EVAP operational. If you have the no start condition again- try opening the hood to allow ambient heat to dissipate faster, spray bottle with some water on fuel rail, fuel lines.

 

[bluesquirrel]

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 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 feed back here on what years?

@2001LC I have a '98 and had the smell symptoms, without the fuel tank pressure issues. I'm in PHX and with drives up to 7000+ in Flagstaff, I never got the tank pressure. My vacuum hoses were old and leaking, so I replaced those as well as all the VSV valves in the circuit.

 

[DTC72]

The only output I can find related is the value the ECM provides in relation to the specified kPa range in the FSM ( not necessarily the psi, inHg, mmHg? parameters provided BlueDriver). Techstream can read this data, not sure how to get that in BlueDriver
View attachment 2349244

Hmmm...so the BlueDriver reading uses inches of H20 (inH2O) in a water column. Conversion is inH2O = kPa x 4.01463 so the FSM max rating you provided (thanks!) of 2.125 kPa = 8.5396 inH2O so that would make my reading of the charts. Unless BlueDriver is messed up and it is actually measuring Pa (not kPa) then I would be well within tolerance. I will reach out to BD.

 

[2001LC]

@2001LC I have a '98 and had the smell symptoms, without the fuel tank pressure issues. I'm in PHX and with drives up to 7000+ in Flagstaff, I never got the tank pressure. My vacuum hoses were old and leaking, so I replaced those as well as all the VSV valves in the circuit.

I've added a lot to post #2. In it you'll see we've solved or 98% solved issue of smell and gas tank over pressure. In that post you'll see over-heating was the main issue.

Your case may be the same, may not. Try this: use some app to read temp through tech stream as you drive. See what you get as fuel smell comes and go. With AC on and off climbing hills and city driving. But before you do, make sure you do not have a fuel leak.

 

[2001LC]

I’ve been thinking about this for a couple of years trying to make sense of it. Here’s my theory on the issue: This condition is less likely due to a singular problem, more likely points to a combination of factors that lead to excess vapor pressure, and collectively contributes to the EVAP system not being able to keep up with and properly manage excess vapor pressure. Let me qualify that I am no expert in thermodynamics. I think the combination of some or all of these various factors impact the fuel vapor issue.

Vehicle Age: Let's be honest, even well maintained 15-20+ year vehicle platforms are not going to be in optimal mechanical condition which contributes to this problem. Further I think when you operate off road, at high altitude, in summer climate; you have to take this into account and ensure you have good mechanical service awareness of your truck and make the appropriate adjustments to mitigate this issue. Below is a compilation of my thoughts on what to be aware of, and where to look for potential issues.

Fuel: Regional blend differences, tank level, fuel quality (adds or lack there of), octane rating, seasonal blend vs summer blend, ethanol content, butane content: more on that below. Note: Fuel blends are different between many different metro markets across the US based on regional pollution requirements which might help explain why this seems more random to those that do and those that dont experience this issue.

Altitude: Higher altitude contributes to increased vapor pressure

High ambient air temps 85~90f+

Excess engine/under hood temps and radiant heat increasing fuel temperature due to:
a.) poorly maintained cooling system: (dirt and debris in radiator, poorly functioning fan clutch, non functioning radiator cap, failing thermostat, low coolant);
b.) lean condition: ( vacuum leaks, exhaust leaks, clogged cats etc)
c.) failing fuel pump: overheating fuel via cavitation, running fuel on low frequently
d.) failing or failed fuel pump resistor: unable to compensate fuel pump speed and over heating fuel
e.) failing or failed fuel pressure regulator: unable to process return fuel flow adequately

Poorly functioning EVAP System
a.) saturated charcoal canister
b.) poorly functioning switching valves/solenoids
c.) partially clogged pressure switching valve
d.) loose fitting or cracked vacuum lines
e.) partially clogged fuel cut off valve
f.) Pinched or kinked vacuum hose

Off Camber Driving at Altitude with 3/4 to full fuel tank in hot weather: my thought that running off camber at various angles, sloshing gas, warm conditions where fuel and vapors expand fuel inside tank the EVAP line gets fuel or condensation in it and cannot process vapor effectively.

FUEL (dynamics) as a key contributor:
I’ve “plagiarized “ some content from various places to articulate my theory:

Region, seasonality of fuel, climate combined with altitude play a big factor in this vapor pressure issue. This doesn't explain away occurrences in late summer but in later spring/early in summer ( June 1) especially with transition from winter blended fuel to summer blended fuels. Especially in 2020 with substantially less fuel sold due to Covid this spring, the transition from winter to summer blend at the pump may be slow due to turnover at both gas stations and in supplier inventory.

What is winter vs summer blend: “Winter blended fuel contains higher concentrations of Butane which is highly volatile- and vaporizes at lower temperatures, in warm conditions it will cause fuel to boil at lower ambient temperatures .”

Consider FUEL VOLATILITY. “The ease with which gasoline vaporizes is called volatility. High volatility gasoline vaporizes very quickly. A low volatility gasoline vaporizes very slowly. Higher octane fuel has lower volatility, and lower octane fuel has higher volatility.”

“Gasoline is composed of a variety of ingredients that evaporate at different temperatures. The faster vaporizing components evaporate at lower temperatures then the slower vaporizing components. Established standards for gasoline volatility (ability to vaporize). “

"Gasoline with lower evaporation temperatures (more highly volatile) starts easier, warms up better and contribute less to deposits but would have more fuel losses and would be more likely to vapor lock. If the gasoline has too low a boiling temperature it may boil in fuel pumps, fuel lines or in carburetors at high operating temperatures. The vapor causes a decrease in fuel flow to the engine resulting in loss of power, rough engine operation or complete shut down of the engine”.

“Gasoline with higher evaporation temperatures (decreased volatility) wouldn’t have the losses or vapor lock problems but would start harder and not warm up as easily with increased deposits and dilution of engine oil. Exhaust emissions could also increase. If the gasoline doesn’t vaporize sufficiently it will be hard to start a cold engine, cause poor warm up and acceleration, and unequal fuel distribution to the cylinders. To minimize the effects of these driving conditions gasoline specifications change from season to season and take into account geographic considerations. To minimize the effects of volatility on the formation of smog there are further limitations during the summer months.”

“A key aspect of gasoline stability is vapor pressure. This is determined by how much pressure builds up inside a sealed fuel container when the fuel is heated to 100°F. A higher vapor pressure suggests a higher concentration of low boiling point hydrocarbons that vaporize under 100°F. Pump fuels with high (12 pounds/square inch, psi) vapor pressures are used in cold weather to prevent engine starting issues due to low temperatures. Pump fuels are limited to 7.8-9psi maximum in warm weather depending on county and state (www.epa.gov). If stored in a vapor tight container the vapor pressure can be maintained for long periods of time. Fuel exposed to the atmosphere can lose light components within a couple of days. Over time as vapor pressure decreases the fuel can become stale. Stale fuel doesn’t evaporate as easily and can cause rough engine idle and hard starting. Butane is a volatile gasoline component used to tailor vapor pressure in accordance with seasonal needs. Cold weather fuel has higher concentrations of butane. Butane has a high blending octane value which helps manufacturers hit their octane targets. The main downfall of butane is that it boils at 32°F. If the fuel tank is vented to atmosphere the butane can start to evaporate out unless the daily temperatures are below freezing. This makes cold weather fuel more susceptible to vapor pressure loss and octane decreases.”

“The higher the temperature, the higher the altitude, the more likely it is that Gasoline vapors build, This tendency is higher in hotter climate and in higher altitude. Ethanol blending affects the vapor pressure. Adding 10% of Ethanol to Gasoline – as is currently done in the USA - drastically reduces the V/L ratio temperature. Therefore a critical vapor liquid ratio, which can cause vapor lock, will be reached at lower temperatures with Gasoline-Ethanol blends than with regular Gasoline “

“Winter specification fuel will not perform well during the summer months and visa verse it is important to ensure adequate inventory turnover to avoid non-compliant situations as the seasonal requirements change.”


Take what you will from my thoughts on this- or add to it. I believe that a properly maintained engine and properly functioning EVAP system should be able to handle the majority of user conditions for city and highway general offroad use driving from sea level to 10,000+ feet anywhere in the country. We know Ethanol attracts moisture, one theory I have is that as fuel in tank heats up and expands, warm moist vapor and condensation propagates and collects at the top of the tank where the cut off valve is and where the outbound evap line from tank to charcoal canister runs- I think condensation and or sloshing fuel when running trail gets into this line making it difficult for vapor to pass, and what does pass moisture saturates the charcoal in the canister making it difficult for the canister process vapor and keep up.. I have experienced some of these issues at 1,000 feet and 12,000. I noticed as I vented the gas cap very warm and moist vapor came out of the tank- for more than a minute. Since then I’ve made substantial improvements/updates to my cooling system, fuel system and engine so I will report back after my high country trip next month to say if any of it helped and if my theory holds any water.

If you want to test your EVAP system there is a very detailed procedure listed in the Emission Control section of the FSM. (attached)

Great write up my friend. We are on the same page here! Properly maintained rigs make so much difference.

 

[DTC72]

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.

Every time this has happened to me if I wait ~15 minutes for cool down it starts right up. A Toyota mechanic told me to tap on the gas tank to disturb the equilibrium in the tank. That to me is a disturbing suggested action and I have not had the nerve to try it.

 

[abuck99]

Hmmm...so the BlueDriver reading uses inches of H20 (inH2O) in a water column. Conversion is inH2O = kPa x 4.01463 so the FSM max rating you provided (thanks!) of 2.125 kPa = 8.5396 inH2O so that would make my reading of the charts. Unless BlueDriver is messed up and it is actually measuring Pa (not kPa) then I would be well within tolerance. I will reach out to BD.

Do you have access to TechStream- you get accurate reading that way.

 

[DTC72]

Do you have access to TechStream- you get accurate reading that way.

Nope. BlueDriver is all I have.

 

[JunkCrzr89]

Nope. BlueDriver is all I have.

Techstream is practically mandatory for this stuff. It has multiple tests that you can run to help pinpoint where the problem is.

 

[2001LC]

I've updated post #2 in this thread. Well worth reading or reading again, as I've added more.

I actually 98% solved this fuel boiling issue, in this 1999 100 series, before starting the thread. I apologies, but I've been very behind in posting, being very busy helping others with their 100 series and 200 series. To make things more difficult, my email service (comcast.net) has blocked ih8mud as spam. Not my PC filters, but at comcast servers for everyone using comcast.net. Wood's is working on it! Then to compound the issue all of my PC and my TV crashed at same time.

I'll go though, as time allows, and read each post in this thread.

I've long held this is not an issue of poor design in the 100 series. I do not believe we all (or any) need to add heat shields next to fuel line as they pass CAT.

I finally I had one to work on, this 99. Your issue may be different. But to get the basic's in line, should be everyone first step...

 

[bluesquirrel]

Agree with the heat shielding. I have an LRA 40 gal tank coming in August and I'm going to refresh the fuel system lines, add shields in various places. I've never had the boiling issue or overheating. But just in case

 

[jerryb]

regardless of what conversions, or numbers or units you guys get, that # from -4.1 to +2.1 is next to zero pressure. Your lungs can blow just under +4. kPa So it should be easy to just say you're over what it should be.

umm..... where is this vapor pressure sensor and how can I see it. TS reads Kpa? I've never looked. In the canister?
I'm guilty of not having a fuel smell, vapor, issue for a few years now.

I only put a shield up on the drivers side. I use to hear it boil all the time.
Seems simple to me, it gets hot, it boils, you can hear it boil, do what you got to do keep it from getting hot. MOTO

 

[gatormark91]

VSVs will DEFINITELY indicate working when tested but still stick. The one on the intake should be checked closely. If that one sticks, you get no vacuum on the canister at all. And again, I'll add this - check for exhaust leaks. Even a small leak is putting 500-800 degree exhaust under the truck, and will boil your fuel. It will be worse if you are towing any trailer, as well, since the trailer messes with the cooling flow of airflow under the truck.