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It totally makes sense to me that there could be a failing valve messing with the system pressure. I can't imagine it being designed in a way that fuel boils out of the tank at 100F without something in the system failing.
You likely have mupile issue to address.
The first vac line going to front of intake manifold. Is always cracky. If never removed, I'll bet it is still tight (not lose, no vacuum leak)
Waht was this temp? "The highest I saw was 120F during the hottest part"1. Your IR temp gun is ok for gathering data but unless you can use it many times per drive per day as well as watch it change as you drive, then it's not really telling you anything. This problem's #1 cause is time, #2 is time spent at low RPM/idle. Because it's heatsoak over time of course all of the points you measure will be within a few degrees at any given time.
2. I have a new fuel pump, new FPR, new fuel damper, new filter, replaced tons of lines, rebuilt my charcoal canister, new radiator, new thermostat, new coolant hoses, new COPs, new plugs, new exhaust, etc etc.
I have done the heat shield mod.
I have used all types of fuel.
I can tell you right now that moving my return line up on to the firewall is the only thing that I did that had a measurable effect on the fuel temperature.
OEM fuel pressure regulator: Amazon.com: Genuine Toyota Parts - Regulator Assy, Fuel (23280-50050): Automotive
OEM fuel pump: Amazon.com: Denso 951-0003 Fuel Pump: Automotive
OEM fuel filter: Amazon.com: WIX Filters - 33875 Fuel (Complete In-Line) Filter, Pack of 1: Automotive
OEM fuel pulse damper: Amazon.com: Toyota 23270-50011 Fuel Pressure Pulsation Damper Assembly: Automotive
Replaced the heatshield with black slightly larger so it fits over without cutting and looks a lil better: https://www.amazon.com/gp/product/B0039Z3R76/?tag=ihco-20
Just got back from wheeling this weekend again over 10k feet and fuel temperature was noticeably lower on the highway up and it took longer to heat up than I was expecting. Maximum temperature was about 5-10F lower than I expected based on conditions. The highest I saw was 120F during the hottest part of the day (88F) and it was 110-113F for most of the day before that (70-80F ambient).
You're running to hot and temp swing to fast. Come by and I'll give a look at why! Just PM, or text or call first with ETA!
I replaced the purge valve on my '99 four years ago to try and combat this vapor issue. It is an expensive little part and it didn't change the amount of vapor release or pressure in the tank. In an weird turn of events, last week a P0441 triggered my CEL (first time I've ever had an emissions code). I replaced the purge valve with the original valve. Now I wait to see what happens.
I installed the LRA 40 gallon earlier this year and haven't made it to the high country yet to test. However, I do have a pretty substantial pressure release from the cap when I go to fill up when its hot outside (+90°). The rollover valve (77380-26010) and tube assembly (77018-60060) were replaced when I installed the tank. The LRA tank sits closer to the driver side cat than the factory tank, so I have some concern about heat soak. I might try some adhesive backed insulation material on the tank near the cat if there is a problem.
Fuel temperature reached 120 maximum.
Water temp 188-194F
Good info, thanks!
I agree with a lot of this after throwing myself at all sorts of new oem parts in the past year to immediately boiling on the trail right off the bat in the spring I was about to give up on my 100. Now I've been running ethanol free consistently the past two weeks with no boiling/venting. Even went above 10k ft last weekend around mammoth gulch area outside rollinsville/Nederland this last weekend and was fine. Any other time I do something like that and I'm generally boiling even at lower altitudes. Will report back if anything changes goes here but so far so good. I'd be curious if 200 series or tundra gas tanks, pumps evap systems tanks in more recent years have some material change we can model for or use newer part to handle E10 fuel?I don't believe it is a defect in design, its a defect in the fuel for the vehicle design. The 100 was designed for gasoline, not ethanol blends with higher evaporation.
In the desire to use more renewable fuels, politicians and the EPA decided that corner cases like EVAP overload at high altitude or very hot ambient temperatures would be sacrificed, the data they collected below shows they knew there was an issue.
I have done multiple trips comparing non-ethanol vs ethanol E10 and never have an issue with non-ethanol.
I think the worst case testing ground is the San Juan Mts. due altitude and availability of non-ethanol.
You have several high passes with one over 13,000 and temperature can get in the 80s
My first trip there in 2017 for HIHs running E10, I had high gas tank pressure and some gas blow by when opening the filler on the high passes.
We were told it was common problem and to not fill tanks above half full, which I did for the rest of the event. Still had high pressure to vent but no gas blow by.
In 2018 the first day had E10 from trip in, and had high tank pressure when venting on the high passes. Next day filled tank to little over half with non-ethanol in Silverton, no pressure on vent on high passes. So decided to go for broke third day filled tank to the top (FULL) with non-ethanol, and headed to top of Black Bear pass (12,840ft) at the pass, opened the filler and no pressure, none!!! My friend in an 80 series found the same results.
In 2019 only used non-ethanol and filled up every time and no pressure on any of the passes including Imogene Pass at 13,114ft. On this trip two friends in 80 series and two friends in 100 series also found no tank pressure on high passes using non-ethanol.
These trips have all been the first week of August.
By the way this is the original factory evaporative emission control (EVAP) system, no changes.
Ethanol blends are neither bad nor good just need to be used in systems designed for them. Since the majority of our fuel is now E10 I think it is good that a number of you are testing modifications to improve how our vehicles deal with E10. Keep up the good work.
Scientific data below.
While ethanol does boil at higher temperature (i.e. has lower vapor pressure) than gasoline, blends have a non-linear relationship.
For blends below about 40% ethanol the vapor pressure can be over 10% higher than gasoline. In order to market E10 the EPA granted a waiver on vapor pressure requirements for E10 as it could not meet the EPA requirement on gasoline.
The following graph is from the National Renewable Energy Laboratory which is part of the US DOE.
From the NREL report.
However, when blended into gasoline at relatively low concentrations the more numerous gasoline molecules disrupt the attractive forces between ethanol molecules and allow the ethanol to readily evaporate, raising the vapor pressure of the blend.
I will be replacing a few fuel and cooling related parts this weekend as it's preventative and I'm nearing 200k anyways, but will report back if there are any changes.
I am not interested in being nitpicked like this. I was off-roading at slow speeds for hours which resulted in a large increase in fuel temperature compared to driving on the highway briefly.
No the temperature is absolutely fine and right on the money.
Several times an hour from start up in the morning until I park back at home at the end of the day. Fuel temperature is measured on the input line right before the fuel filter.
You do recall correctly and I would not be able to fit everything I've done in my signature line. Test assured I'm taking this problem seriously and I work on my own vehicle so I've looked at the whole fuel system front to back to address the weaknesses I've seen. And I'll say it again the best mod I did was move the return fuel line up away from the engine but no one will believe me or listen anyway.
I know because I've searched this very forum and have found posts about it from before my truck was even manufactured.
Agree the fuel is a band aid here, just saying it resolves the issue for me as of now. I'm still closely looking at my cooling system now to see if something is going on there. Will update from my end as well. Agree basing all my trips/travel around fuel is not optimal!!That's great that it's working for you, butit just seems like a temporary fix. I cannot get ethonal-free gas for 100s of miles away from where I am and it just seems like a huge inconvenience to look for ethanol-free gas stations just to get into the mountains. Just went up to the Sierras this past weekend (7000') and the same problem occurred- vapor leak and built up pressure.. Conditions were 90 degree weather with fully loaded truck. This only happens when going to elevation and only when the truck is working hard. Going downhill, there is absolutely no problem at all and when releasing the gas cap, there is little to no pressure- not even a hiss. I am however still feeling a hesitation when foot is constant on the gas when cruising on the freeway, seems like it's fuel related. Problem, disappears when in cruise control.
That is correct. You may want to replace the spring clips too if they're stretched.
Hmm interesting stuff. What are your fuel temperatures?I don't believe it is a defect in design, its a defect in the fuel for the vehicle design. The 100 was designed for gasoline, not ethanol blends with higher evaporation.
In the desire to use more renewable fuels, politicians and the EPA decided that corner cases like EVAP overload at high altitude or very hot ambient temperatures would be sacrificed, the data they collected below shows they knew there was an issue.
I have done multiple trips comparing non-ethanol vs ethanol E10 and never have an issue with non-ethanol.
I think the worst case testing ground is the San Juan Mts. due altitude and availability of non-ethanol.
You have several high passes with one over 13,000 and temperature can get in the 80s
My first trip there in 2017 for HIHs running E10, I had high gas tank pressure and some gas blow by when opening the filler on the high passes. Since it is a 100 series event there was a lot of venting going on. We were told it was common problem and to not fill tanks above half full, which I did for the rest of the event. Still had high pressure to vent but no gas blow by.
In 2018 the first day had E10 from trip in, and had high tank pressure when venting on the high passes. Next day filled tank to little over half with non-ethanol in Silverton, no pressure on vent on high passes. So decided to go for broke third day filled tank to the top (FULL) with non-ethanol, and headed to top of Black Bear pass (12,840ft) at the pass, opened the filler and no pressure, none!!! My friend in an 80 series found the same results.
In 2019 only used non-ethanol and filled up every time and no pressure on any of the passes including Imogene Pass at 13,114ft. On this trip two friends in 80 series and two friends in 100 series also found no tank pressure on high passes using non-ethanol.
These trips have all been the first week of August.
By the way this is the original factory evaporative emission control (EVAP) system, no changes or part replacement.
Ethanol blends are neither bad nor good just need to be used in systems designed for them. Since the majority of our fuel is now E10 I think it is good that a number of you are testing modifications to improve how our vehicles deal with E10. Keep up the good work.
Scientific data below.
While ethanol does boil at higher temperature (i.e. has lower vapor pressure) than gasoline, blends have a non-linear relationship.
For blends below about 40% ethanol the vapor pressure can be over 10% higher than gasoline. In order to market E10 the EPA granted a waiver on vapor pressure requirements for E10 as it could not meet the EPA requirement on gasoline.
The following graph is from the National Renewable Energy Laboratory which is part of the US DOE.
From the NREL report.
However, when blended into gasoline at relatively low concentrations the more numerous gasoline molecules disrupt the attractive forces between ethanol molecules and allow the ethanol to readily evaporate, raising the vapor pressure of the blend.
Yup. Easy and cheap to replace all those vac lines.
This is a good point- i hear rattling from my exhaust and can smell gas even when tank is 1/4 full
