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

 

[TeCKis300]

Fuel tank shielding​

Even though the fuel tank is not necessarily around the hottest parts of the underbody, it has the most surface area exposure so this is a great place to start. The stock fuel skid already contributes as a heat shield, and has another metal shield alongside most of the length. Still, we can do better here to give it more coverage and insulation.

The peel and stick product above is fun and easy to do. I didn't have enough product on hand, but it would be great to put full sections on the sides of the tank. Focusing on the forward nose to extend coverage higher and augment the shielding there. Then on the longitudinal side against the driveshaft.

Here's what the tank looks like for reference. Peel and stick can be done with tank in place.
Forward snout of tank and stock skid is probably the most useful insulation. Add additional insulation and extend insulation upwards on the skid sides for more coverage.

Note stock gray shield alongside which is probably more for protection against the driveshaft. Could be good to add additional insulation to as it is also against the exhaust resonator which has a lot of surface area to radiate heat.

Adding shielding to forward part of the tank where it comes nearest to the exhaust. I didn't have enough product and will probably go back and add. I opted to extend a part of the shielding bridging to the heat shield on the underbody. Cleaned with windex, cut shield to shape, peel and stick. Satisfying.

Add a full insulating section to the long side of the gas tank against the driveshaft/exhaust resonator. (I still need to do)

Aux Tank (LRA) tank shielding​

For those that have the LRA aux tank, it's metal, and runs really close to the muffler. Probably a large contributor to gas heating and would be good to insulate.

Fuel Line Shielding Around Exhaust​

Fuel through the fuel line and returning from the motor has been identified as a major source of heat. Probably not a surprise given its routing alongside major exhaust components, hot motor, and return. This part is focused on the lines routed under the chassis.

The lines start on top of the tank. Crosses over from the passenger to driver side over exhaust in the mid-section. Then runs along the driver frame rail near exhaust plumbing, past and very close to two catalytic converters, and up to the engine bay. It is shielded all along the run behind metal covers, but in a heat soak situation, can use additional insulation. Anywhere that the lines come near exhaust components would be a good candidate to peel and stick.

Crossover rail. Good to leave drain holes open

Right near secondary converter. Add insulation over the existing fuel line cover

Add insulation over stock gray shielding. Add insulation over the shielding nearest the primary cat.

 

[TeCKis300]

Fuel Line Shielding in Engine Bay​

This is a bit of a PITA as the main lines to wrap are deep in the bay and it's a one hand operation.

Looking at the drivers side, alongside the engine, you'll see 3x ~1/4 lines routed in parallel coming from deep in the engine bay by where the transmission and primary cat are. They kind of zig sag. 2 of these are fuel lines (to and return). 1 is to the top of the intake manifold and is the charcoal canister purge.

Wrap the 2 fuel lines.

Use 3/8" insulation wrap in the for the ones furthest down. The zig zags make it hard to do one continuous insulation run. I found it easiest to do straight 3-4" sections and not try to wrap around the bends.

Use the 5/8" insulation wrap at top most lines that go to the fuel rails. These already have some rubber insulation so they are larger diameter. Again, don't try to do a single continuous wrap and make segments for the straighter runs. It's okay to leave some line exposed as this is a game of reducing a degree of surface area exposed to heat.

I need to buy more wrap as I wasted some trying to do continuous runs but you get the idea.

 

[teejnut]

Thanks for posting this. Will have to try it out. Was on some trails in 100 degree weather near Big Bear and experienced the fuel vapor/boiling issue.

 

[speakout525]

This is great. I vent often and sometimes boil here in Utah. On recent trip through Idaho, Oregon and N.Cali, I almost expected to smell it daily it happened so much. High atmospheric temps, elevation, towing and hill climbs made it a given. I will give these a try and see what happens. Thanks a ton!

 

[clrussell]

So what happens if the fuel boils like your talking?

Check engine Christmas tree? Or drive ability problems?

 

[speakout525]

So what happens if the fuel boils like your talking?

Check engine Christmas tree? Or drive ability problems?

I'm not sure what would happen if extended travel, but I just stop and let the vehicle rest.

 

[kcjaz]

So what happens if the fuel boils like your talking?

Check engine Christmas tree? Or drive ability problems?

Good question. I've had "the boil" once at the top of Red Cone. No CEL or anything except the smell of gas and visible overflow of gasoline at the gas cap. Min was minor. Another rig was massively boiling and was significantly overflowing the cap cap in a big way with gasoline running down the side of his truck. I was a bit freaked but owner of said rig was not overly concerned. "yeah, it does this sometimes".

Some throw CEL or evap codes which can just be cleared by a code reader. I have not heard of this forcing the truck into "limp mode". This biggest practical issue I have heard about is the inability to pump gas into a tank tank that is boiling as the vapor shuts the pump off. I've heard of people going to a car wash or using a garden hose to cool the fuel tank.

 

[TeCKis300]

Thanks for posting this. Will have to try it out. Was on some trails in 100 degree weather near Big Bear and experienced the fuel vapor/boiling issue.

Yup, that's one of the spots where I've had an issue. Some mild fuel fumes. Headed out to Big Bear again in a couple weekends for some hot crawling at elevation. Wish I had empirical data with a thermocouple in the fuel system, but will have to settle for monitoring symptoms.

 

[clrussell]

Perfect thank you.

Good question. I've had "the boil" once at the top of Red Cone. No CEL or anything except the smell of gas and visible overflow of gasoline at the gas cap. Min was minor. Another rig was massively boiling and was significantly overflowing the cap cap in a big way with gasoline running down the side of his truck. I was a bit freaked but owner of said rig was not overly concerned. "yeah, it does this sometimes".

Some throw CEL or evap codes which can just be cleared by a code reader. I have not heard of this forcing the truck into "limp mode". This biggest practical issue I have heard about is the inability to pump gas into a tank tank that is boiling as the vapor shuts the pump off. I've heard of people going to a car wash or using a garden hose to cool the fuel tank.

 

[teejnut]

Yup, that's one of the spots where I've had an issue. Some mild fuel fumes. Headed out to Big Bear again in a couple weekends for some hot crawling at elevation. Wish I had empirical data with a thermocouple in the fuel system, but will have to settle for monitoring symptoms.

Let us know the results! It was quite annoying, I was with a GX460 and a late 2nd gen Tundra. Neither had this issue.

 

[TeCKis300]

Added to the above post detailed wrapping of fuel lines in the engine bay.

Let us know the results! It was quite annoying, I was with a GX460 and a late 2nd gen Tundra. Neither had this issue.

Yup. I was with 2x Raptors, 1x LC100, GX460, Xterra and mine was the only one venting vapors. Chink in the otherwise steadfast 200-series armor.

Looking underneath these rigs, a big contrast is how tucked up the 200-series driveline is in the frame. Nothing extends below. Whereas every other rig had major components and gas tank extend well below the frame.

 

[Pierce]

The 80 series has the same issue. In that series it was because of a failed charcoal canister.

My 200 series does not boil the fuel yet but when I was installing the aux tank I noticed that my charcoal canister pre-filter was loaded with fine dust. My P.O. spent a ton of time on fine dirt roads and I usually have to rinse off pounds of the stuff any time I’m working in a new area.

I knocked about 1/2 cup of dust out and had to run a water hose through it for 5 minutes before the water was clean. That’s a long way of saying check your charcoal canister pre filter if you spend a lot of time off road. It may be clogged. It’s just a plastic box.

Stock photo from LRA instructions.

 

[TeCKis300]

The 80 series has the same issue. In that series it was because of a failed charcoal canister.

My 200 series does not boil the fuel yet but when I was installing the aux tank I noticed that my charcoal canister pre-filter was loaded with fine dust. My P.O. spent a ton of time on fine dirt roads and I usually have to rinse off pounds of the stuff any time I’m working in a new area.

I knocked about 1/2 cup of dust out and had to run a water hose through it for 5 minutes before the water was clean. That’s a long way of saying check your charcoal canister pre filter if you spend a lot of time off road. It may be clogged. It’s just a plastic box.

Stock photo from LRA instructions.

View attachment 3393740

Good point and perhaps a possible separate contributor.

My charcoal canister is relatively new with 5k miles as I changed prior for LRA aux tank related reasons. My filter and aftermarket cone filter are also pretty clean as I maintain them regularly due to off-roading in sand and silt in my region.

 

[Catskills]

So what happens if the fuel boils like your talking?

Check engine Christmas tree? Or drive ability problems?

My dash went Xmas tree in July and the truck went into limp mode on a significant incline while I was towing my camper. It was actually pretty scary for me; I was alone with spotty service, and I was very lucky I could get off the road in a safe place and that I code clear the codes.

Resetting the codes worked. But because I was about to live on the road all summer, I had Toyota verify that the truck was fine, and they promised it was. They said it was because I didn't tighten the gas cap. I didn't think that was right, and in Colorado I bought a new gas cap thinking maybe that would help.

Since then has thrown codes more times than I could count (NY to UT and now in VA) but once I came down in elevation it's been fine. I actually designated a tablet just to clear codes because I was worried this would happen while towing on the interstate, which it has.

I said this in the towing thread, but multiple fill-ups of non-ethanol did not alleviate the problem at all (it definitely helped my 100 which also boiled gas).

Someone in the 100 section did a ton of work on this but I can't remember his handle.

 

[clrussell]

My dash went Xmas tree in July and the truck went into limp mode on a significant incline while I was towing my camper. It was actually pretty scary for me; I was alone with spotty service, and I was very lucky I could get off the road in a safe place and that I code clear the codes.

Resetting the codes worked. But because I was about to live on the road all summer, I had Toyota verify that the truck was fine, and they promised it was. They said it was because I didn't tighten the gas cap. I didn't think that was right, and in Colorado I bought a new gas cap thinking maybe that would help.

Since then has thrown codes more times than I could count (NY to UT and now in VA) but once I came down in elevation it's been fine. I actually designated a tablet just to clear codes because I was worried this would happen while towing on the interstate, which it has.

View attachment 3393823

I said this in the towing thread, but multiple fill-ups of non-ethanol did not alleviate the problem at all (it definitely helped my 100 which also boiled gas).

Someone in the 100 section did a ton of work on this but I can't remember his handle.

Good to know, I have a cheap code reader in mine.

Last year mine never hesitated on the evap issue on. 4K west road trip. How we we didn’t spend a ton of time on trails at elevation.

Headed west in a month for 10 Days and just keeping an eye out.

 

[TeCKis300]

My dash went Xmas tree in July and the truck went into limp mode on a significant incline while I was towing my camper. It was actually pretty scary for me; I was alone with spotty service, and I was very lucky I could get off the road in a safe place and that I code clear the codes.

Resetting the codes worked. But because I was about to live on the road all summer, I had Toyota verify that the truck was fine, and they promised it was. They said it was because I didn't tighten the gas cap. I didn't think that was right, and in Colorado I bought a new gas cap thinking maybe that would help.

Since then has thrown codes more times than I could count (NY to UT and now in VA) but once I came down in elevation it's been fine. I actually designated a tablet just to clear codes because I was worried this would happen while towing on the interstate, which it has.

View attachment 3393823

I said this in the towing thread, but multiple fill-ups of non-ethanol did not alleviate the problem at all (it definitely helped my 100 which also boiled gas).

Someone in the 100 section did a ton of work on this but I can't remember his handle.

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.

 

[Catskills]

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.

I tried all manner of fuel. Did two tanks of premium in Colorado, then two non-ethanol. Neither made a difference.

Stock skids. No aux tank. Nothing other than a bumper and lift to complicate the truck.

I'm really frustrated that I thought I was done with this when I replaced my 100 with this truck.

That 100 poster was not the one I was thinking of...I'll try to find him.

 

[Catskills]

It was @2001LC

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

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: Coolant system if first on the list, must be operating as designed. Which radiator fins cleaning...

forum.ih8mud.com

 

[staggrlee]

Subscribed. Luckily have yet to experience this with the 200, but i know I will...

Simple solution? Route the fuel line up into the center console cool box with a copper coil from pappy's still.

Seriously though, I've battled this for years with my 100 and came to the conclusion there is only mitigation and no fix over 5,000 feet in altitude. Supercharger, skids, armor, aftermarket exhaust, sub-tank etc. Too many exacerbating factors there.

The only thing that seems to help is running the highest octane I can find (which I have to regardless) preferably ethanol free, keeping tanks as full as possible to minimize vapor pressure, and never, ever, opening the cap to vent unless I want to boil off a 1/4 tank of gas... While someone smoking a cigarette comes over to see what the hold up is.

At this point I'd consider figuring out how to hack a Helton heat exchanger and a Sureflo pump to heat a tank of water for a shower at the end of the day.

<Edit> Should also mention that shutting off the truck frequently when stopping trail side in groups makes matters worse. Engine compartment heat soak definitely doesn't help, better to idle it if it's a shortish stop.