DIY Fuel Heating/Boiling Mitigation

[TeCKis300]

This thread is not quite a comprehensive fix (yet), but hopefully gets the ball rolling to improve upon fuel venting/boiling in the 200-series. I don't have complete answers and hoping there will be continued contributions by the hive mind. This is one of those issues that may not have a single magic bullet fix. It's a balance of use cases and mods that exacerbate getting heat into the fuel system versus mitigations sufficient to overcome heating factors.

Synopsis of Problem​

Fuel has increased volatility and vapor pressure known as Reid vapor pressure (RVP), at elevated temperature or reduced atmospheric pressure, or a combination of both. Commonly experienced when slow crawling on trails with minimal airflow and lots of heat soak, combined with trails at 6k+ ft elevation. To the point that fuel vapors can vent and actually boil. The only thing we can really control is heat input into the fuel. If someone were inclined to instrument the problem, it is singularly fuel temperature to be watched and managed.

There's some other variables to this. Fuel composition and added ethanol can contribute to the volatility of fuel. Short answer is its best to avoid ethanol compositions that has allowances for higher RVP, buy fuel from stations at higher elevation, use high octane that is inherently less volatile, and fill tanks to higher levels to increase thermal mass. Stock rigs can experience this. Aftermarket modifications like skids, aux gas tanks, and even bumpers can exacerbate the issue, disrupting cooling airflow, trap heat, and increase heat input to the fuel system. Many rigs experience this but perhaps the cruiser series is particularly susceptible as the driveline and gas tank tends to be tucked up higher and tighter under the chassis trapping more heat.

Solution Template​

@J1000 gets credit for analysis and identification of tested mitigations for the 100-series. Short of that being available for the 200-series, and with the 200-series sharing many of the same layout and design aspects, this should be a great template to follow. Worth a read and it gives us a strong clue as to which mitigations may contribute the most.

I was under my truck doing some more mods. And since I have a fuel temperature sensor, I can tell what works and what doesn't. If you want to argue with me then just put me on ignore, please. If you want to prove me wrong, get your own fuel temperature sensor. Here's two good ones: Amazon.com: Innovate Motorsports 3904 MTX-D Dual Gauge Kit -Ethanol/Fuel Temp, 1 Pack: Automotive and Amazon.com: Zeitronix ECA-2 Ethanol E% Content Analyzer Kit with Blue Display Gauge: Automotive If you have constructive criticism, please post it.

Reminder, this thread is about boiling fuel. Your #1 point of reference should be the fuel's temperature. Everything else is secondary. No, I do not expect everyone to have fuel temperature because it's not available stock or without some elbow grease but I've got one.

The following are my mods to combat fuel temperature in order of their effectiveness. I have also done lots of work on my evap system which I've detailed in this thread: 100 Series Charcoal Canister Replacement Truck is well maintained and has many new parts over the last 1-2 years, too many to list but if you are thinking "but did you replace your _____" the answer is probably YES!


#1: Extensive heat shielding. Earlier in this thread there was talk about extra shielding on the catalytic converters, but I found recently over the past few weeks that there are far more important areas to add heat shielding. I've been doing this by driving a lot and then scooting under the truck on my creeper and feeling around with my hands and figuring out where things are hot and where they aren't and then doing it again.

There is an area here on the fuel tank where the stock metal guard doesn't cover and there is no heatshield between it and the exhaust pipe.

Bare fuel tank exposed within 12" of exhaust pipe (darker tank shield seen below exposed tank side with rough texture):

Here and on the tank shield itself I used adhesive backed heatshield material: Amazon.com: Second Skin Thermal Block - Automotive Heat Shield - Reflective Aluminum, Insulation & Adhesive (8 sq ft, 4 Sheets) - Made in USA: Automotive - https://amzn.to/3juiU2t This stuff blocks the radiant heat with the silver metal barrier but also insulates with a cloth layer underneath and sticks with adhesive which makes it easy to put anywhere. I use this small roller to help get a good bond: Amazon.com: LUMITECO Automotive Car Audio Sound Deadening Application Wheel Roller, Heat Abatement Mat Wallpaper Application PU Smoothing Tool Seam Roller: Automotive

I did the whole side of the fuel tank. I also extended the factory heatshield in a few more places:

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.

#2: Moving return fuel line off the engine to the firewall. This just eliminated the steel return fuel line that is bolted directly to the engine cylinder heads on the rear of the engine reducing the amount of heat returned to the tank from the fuel rails. I also covered the fuel line as well as the rest of the lines with heatshield: Amazon.com: Design Engineering 010448 Cool-Tube Extreme Heat Reflective Sleeve, 0.75" x 9' - Black: Automotive - https://amzn.to/2ZZs0ds

#3: Catalytic converter and fuel line shielding: These were the first mods I did to try and combat fuel temperature, but I would only rate them #3 on my list. Every other mod was more effective at lowering the fuel temperature. I have no doubt this mod is effective in some way, but not as much as the others. If doing heatshielding under the vehicle, then this should be done no matter what anyway IMO. It's also the easiest of all the mods. I used this heatshield for the fuel lines: Amazon.com: DEI 010441 Cool-Tube Extreme Heat Reflective Sleeve, 0.5" x 9' - Silver: Automotive - https://amzn.to/2WYqZjS

#4: Passive dual-pass finned fuel cooler. More of an experiment than anything I bought this inexpensive multipurpose cooler and plumbed it to the return line right before the fuel tank. I used quick connect fuel connectors so that if there is ever a problem with the cooler I can simply disconnect it and return the lines to stock without any tools. I placed it in the rear area above the frame rail. This area is always cool to the touch compared to the rest of the vehicle when I have been poking and probing for the last few weeks, it gets a surprising amount of air flow.

First I set it up to pressure test:

It passed.

I

Looking inside:

Mounted above the frame rail by the evap canister away from danger.

I used this 12" fuel cooler: Amazon.com: HotRod99 12" Satin Aluminum Finned Dual Pass Heat Sink Cooler Transmission Cooler Black Includes Two 1/4 NPT Fittings: Home & Kitchen - https://amzn.to/2WYwxe4
Some 5/16 Gates fuel hose: Amazon.com - https://amzn.to/302b4D9
and 1/4 NPT to 5/16 fittings: Amazon.com - https://amzn.to/3044yMe


Before doing these mods my fuel temperature would routinely get to be 30-40F higher than ambient and sometimes even 50F or more if the tank was low and/or it had been hours on the trail etc. After doing these mods the fuel now stays between 10-20F above ambient even when low, though I have not done a long offroad trip with the newest mods.

This is about the hottest fuel temp I've recorded to date (127F), though I would bet it gets even hotter. This was before mods. This was at 1/4 tank of fuel driving home in 95F ambient temperature probably 3-4 hours running non-stop. I'm waiting for similar conditions to record a snapshot of the temperature now after all of the mods.

This is not an all or nothing, with each added mitigation potentially buying more margin to managing fuel venting/boiling. It's fully possible the issue can't be fully solved but added margin is worth the effort IMO.

1. Fuel tank shielding
a. Aux tank shielding
2. Fuel line shielding around exhaust
3. Fuel line shielding around engine
4. Fuel cooler

Insulation Products​

Amazon product ASIN B000CEM3O0
Need 3/8 and 5/8" wraps
Amazon product ASIN B079S1XLM7

 

[kcjaz]

So I was reading up on inter-chillers after a post here on the topic and it made me think of fuel cooling….

The HX is an additional condenser put in the AC circuit. I suspect the HX isn’t designed for gasoline but potentially you could add an additional water loop to a fuel cooler. This would be getting a bit complicated and expensive but I’d would be cool!

Toyota Archives – Fi Interchillers Online Store

Toyota Vehicles We keep everything in stock, unless stated otherwise

fiinterchillers.com

 

[skrypj]

I think this just happened to me this weekend. I was up at 10,000' offroading on an 85F day. At one point my wife and I had to get out of the LX to move a tree off the trail and I got a pretty strong wiff of gasoline.

I am semi-annoyed that I have to fix this now.

 

[TheGrrrrr]

I think this just happened to me this weekend. I was up at 10,000' offroading on an 85F day. At one point my wife and I had to get out of the LX to move a tree off the trail and I got a pretty strong wiff of gasoline.

I am semi-annoyed that I have to fix this now.

Those are the three most common variables:

1. Altitude
2. Low Speeds/Off-roading
3. High-ish Temps - Not necessarily super hot even, seems dependent on elevation, which is to be expected.

I have also experienced this with moderate elevations 3,700ft near Hite, UT to Hanksville, UT at 4,295ft and high temps over 100f, but at highway speeds.

also on I-17 driving to Flagstaff going from 110f in Phoenix up to 90f in Flagstaff, again all highway speeds.

 

[linuxgod]

I think this just happened to me this weekend. I was up at 10,000' offroading on an 85F day. At one point my wife and I had to get out of the LX to move a tree off the trail and I got a pretty strong wiff of gasoline.

I am semi-annoyed that I have to fix this now.

If it’s not a regular occurrence you can probably ignore it. I had this happen in 2017 as I was pulling a trailer to the top of grand Mesa at 10k’. I stopped for a photo and could smell it. But I didn’t have the issue again for several years. Even still I only have it at high altitudes on trails.

If it’s happening frequently then yeah…

 

[skrypj]

If it’s not a regular occurrence you can probably ignore it. I had this happen in 2017 as I was pulling a trailer to the top of grand Mesa at 10k’. I stopped for a photo and could smell it. But I didn’t have the issue again for several years. Even still I only have it at high altitudes on trails.

If it’s happening frequently then yeah…

I live at 6500’ and can be at 11,000’ within 20 minutes of my house so I think it’s going to be fairly regular. Our summer activities include paddleboarding at remote lakes in the national forest behind our house and most of them are at 9-10000’

Slow offroading would make a lot of sense because the flow rates through the fuel lines are low, so it can heat up more, and air flow under the chassis is low.

 

[bloc]

I live at 6500’ and can be at 11,000’ within 20 minutes of my house so I think it’s going to be fairly regular. Our summer activities include paddleboarding at remote lakes in the national forest behind our house and most of them are at 9-10000’

Slow offroading would make a lot of sense because the flow rates through the fuel lines are low, so it can heat up more, and air flow under the chassis is low.

High or low flow rates the fuel system will be really good at transferring heat from the engine bay to the tank. Crawling also increases underhood temps so we have convection heating the rails on top of conduction.

I personally feel a fuel cooler to remove heat before it returns to the tank is the proper fix for this problem.. excited to see what people come up with on this.

 

[TeCKis300]

I recently did a body lift. I'm hopeful that it may help ventilate the undercarriage somewhat to reduce fuel heating. The stock body sits pretty tight to the chassis rails with about 1/4" clearance all around. As I did a 3/4" BL, that'll increase it to 1", which should greatly open up airflow. At least that's the hope.

 

[residualboulders]

I've had the boiling issue twice. Once at about 9k elevation, probably close to 90 degrees and both tanks pretty full. It was a steep trail in Northern UT, we crawled in low range and gained elevation pretty quickly. It boiled hard and built up a ton of pressure. It was honestly unsettling. I cracked the cap for quite a while to release the pressure. When we could no longer hear the boiling and hissing from pressure I opened it - fuel spewed out the fill neck.

Second time I was in Canyonlands at about 5k elevation. Also crawling in low range and about 80 degrees out. Not a ton of elevation gain. This time the pressure was no where near like the first time, but my check engine light came on with a message to take it to a dealer (light never came on the first time). I figured it could be the boiling so I stopped and checked. Sure enough. Next morning no check engine light and no problems on other trails we did.

At the suggestion of Long Range America I wrapped my exhaust with some Heatshield Volcanic material. I considered using some heat shield as @TeCKis300 has suggested but was concerned it would trap moisture and cause my tank to rust prematurely. I'm in a snowy climate for a good part of the year. I'm not 100% convinced wrapping the exhaust is going to fix the issue. I guess we will see. I've been thinking about fabricating a heat shield for the tank or for the exhaust in addition to the wrap.

 

[skrypj]

Also remember that insulation will prevent(reduce) the tank from giving off heat. If you wrap the exhaust and eliminate the heat source, then you probably want the tank to be uninsulated so that ambient air can keep it cool

 

[TeCKis300]

Also remember that insulation will prevent(reduce) the tank from giving off heat. If you wrap the exhaust and eliminate the heat source, then you probably want the tank to be uninsulated so that ambient air can keep it cool

True and could further minimize some of the hottest radiant heat sources. Most of these hotter elements already has stock heatshielding. An LRA aux tank could benefit from this strategy.

There is still superheated engine bay air channeled through the underbody that convectively heats things.

 

[TheGrrrrr]

I've come to the conclusion that living in AZ and frequently wheeling at high elevations, there just is no passive solution to mitigate heat in these conditions. The only solution is to cool the heated fuel in the return line before it reaches the tank. Other climates mayve solve with airflow, shielding etc but not here, not spending time in AZ, UT and CO. I just ordered the following:

• Derale 13750 Atomic-Cool Remote Cooler , Black
• EVIL ENERGY 6AN PTFE Fuel Line Kit,AN6 E85 Nylon Braided Fuel Hose 16FT(5/16Inch ID)
• Engine Transmission Oil Cooler In-Line Hose End AN Thread-on Fitting Adapter Thermostat Temperature Electric Fan Switch Sensor Kit (140'F On - 125'F Off, 6AN)

I suspect the key is figuring out where to mount it and where best to splice into the return lines. Heads up @Cruiserhiggs, its time to solve this problem once and for all.

Parts are here:

 

[Romer]

I missed this thread before and just added it to the FAQ in the modifications section under fuel.

Any progress on the fuel cooler or other mitigation techniques? Any data on how the exhaust insulation helped?

 

[TeCKis300]

Got to the top of White Mountain Big Bear where I previous had fuel vapor issues. Very similar conditions, 85-95 degrees in September, 7,800ft, after driving and crawling for a few hours.

No fumes this time.

Not declaring succuss but the situation is definitely improved between the added insulation and body lift.

 

[residualboulders]

Got to the top of White Mountain Big Bear where I previous had fuel vapor issues. Very similar conditions, 85-95 degrees in September, 7,800ft, after driving and crawling for a few hours.

No fumes this time.

Not declaring succuss but the situation is definitely improved between the added insulation and body lift.

View attachment 3742989

Good to hear. I had some on Elephant hill trail this spring. Added insulation and am returning to white rim this week. We shall see if it helped.

 

[CanadianRockyCruiser]

Got to the top of White Mountain Big Bear where I previous had fuel vapor issues. Very similar conditions, 85-95 degrees in September, 7,800ft, after driving and crawling for a few hours.

No fumes this time.

Not declaring succuss but the situation is definitely improved between the added insulation and body lift.

View attachment 3742989

I will therefore declare to my wife that my body lift is for the purpose of mitigating unburned fuel emissions and it's about environmentalism. Body lift for the planet!

 

[TeCKis300]

Taking the opportunity to add some insulation to the crossover fuel lines at the rear of the motor while re-sealing the valley plate. These are already rubber lines so not sure how much it'll help, but it can only cut down on BTU transfer into the fuel. Every bit counts. On the 100-series, this line was steel and shielding and moving it to the firewall was identified as #2 most significant mitigation.

Was debating to cover the rails at the side too, but they are already insulated to a degree by factory foam isolators (not seen here). They are also at the top of the motor where it's cooler than down in the vee.

 

[Markuson]

Towing is stressful enough at times but getting limp mode on top of it. I'm not sure many of us have seen limp mode in hard running on the freeway in a similar fashion. Could be fuel heating or could be other things? Non-ethanol fuel could help but IMO with fuel heating, there's no single silver bullet fix. It's going to be multiple mitigations, especially if the vehicle has mods that exacerbate the issue? I see you have a front bumper, is there other mods like skids, LRA Aux tank, etc?

You might try premium grade fuel for kicks to see if that makes any difference as that has lower vapor pressor and higher anti-detonation properties aka octane.

The 100-series learnings by J1000 are there quoted in the first post.

Nah. I boil as fast and even faster with both non-ethanol, and premium with or without.
Utah or Colorado gas…plus altitude = boiling.
Been happening my 200 for many years now.
Solution… I keep a phisically switched OBD2 plugged in 24/7 (physical power switch in-line because OBD2 can seriously drain battery otherwise.

Keep at it if you like… but its really not a big deal. Just an annoyance. No manner of fiddling has ever made a bit o difference.
Confirmed this yet again in Ouray…again…in Moab…as always…on Utah highways full speed……
My 10 year conclusion?
Meh. Keep a reader handy. Teset evap codes…and done in less than 10 seconds—even while driving if I’m distracted or just in a hurry on start-up.

Evap codes still pass smog.
No big deal.

 

[Hoosier Daddy]

Living in Colorado at (only) ~7200 ft, I can get my fuel to boil pretty consistently on demand. If I drive home and park in the driveway and then come back just a few minutes later to move the 200 into the garage, I'll hear the fuel boiling for a few seconds after shutting the engine off the second time. If I just park it directly into the garage the first time (without time to heat-soak), I won't hear the boiling. Never any codes or anything and it doesn't come out the gas door (though it did bubble out on Ophir pass).

I should try this with my son's 100 Series next time he's home from college.

 

[TeCKis300]

Nah. I boil as fast and even faster with both non-ethanol, and premium with or without.
Utah or Colorado gas…plus altitude = boiling.
Been happening my 200 for many years now.
Solution… I keep a phisically switched OBD2 plugged in 24/7 (physical power switch in-line because OBD2 can seriously drain battery otherwise.

Keep at it if you like… but its really not a big deal. Just an annoyance. No manner of fiddling has ever made a bit o difference.
Confirmed this yet again in Ouray…again…in Moab…as always…on Utah highways full speed……
My 10 year conclusion?
Meh. Keep a reader handy. Teset evap codes…and done in less than 10 seconds—even while driving if I’m distracted or just in a hurry on start-up.

Evap codes still pass smog.
No big deal.

That sounds like a workaround and if that works for you, great. I've been in that spot too, without my OBD-II dongle, stuck in 4lo, 3 days deep in the backcountry. Had to pull my battery to get it back into 4hi.

I'd rather not constantly reset my OBD and fix the root issue. There's things like learned fuel trims and timing tables that need to be re-learned each time.

In regards to battery drain, I use this dongle that lives permanently in the port. No battery drain issues as it has sleep features.

https://www.amazon.com/ScanTool-OBDLink-Bluetooth-Professional-Diagnostics/dp/B00H9S71LW

 

[Markuson]

That sounds like a workaround and if that works for you, great. I've been in that spot too, without my OBD-II dongle, stuck in 4lo, 3 days deep in the backcountry. Had to pull my battery to get it back into 4hi.

I'd rather not constantly reset my OBD and fix the root issue. There's things like learned fuel trims and timing tables that need to be re-learned each time.

In regards to battery drain, I use this dongle that lives permanently in the port. No battery drain issues as it has sleep features.

https://www.amazon.com/ScanTool-OBDLink-Bluetooth-Professional-Diagnostics/dp/B00H9S71LW

No qualms with your continued search. But after many years of it…from one stock setup to heavy builds… altitude, heat & more… its just not worth fretting over sny more.

As I’ve noted for years…never once have I had boiling gas using California fuel…even at high altitude and heat. Only with Utah or Colorado fuels. So… meh… Carry on.