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://www.amazon.com/Second-Skin-Thermal-Block-Automotive/dp/B084BS715K?dchild=1&keywords=heat%2Bshield%2Badhesive&qid=1625150357&sr=8-3-spons&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUFOSlhCTUM0TFgzMFUmZW5jcnlwdGVkSWQ9QTA4MjQ4NzIyT0lDSzYwOVRJSlVIJmVuY3J5cHRlZEFkSWQ9QTA0NDc2MjczRTJCQTlWRUxMMUYyJndpZGdldE5hbWU9c3BfYXRmJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ&th=1&linkCode=sl1&tag=imddd-20&linkId=9544ff7a8047c7e764ef98b1e1d93c9d&language=en_US&ref_=as_li_ss_tl 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://www.amazon.com/gp/product/B0039Z3R76/ref=as_li_ss_tl?ie=UTF8&psc=1&linkCode=sl1&tag=imddd-20&linkId=6a63ffcea02ab838474c6eb0ace27470&language=en_US

#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://www.amazon.com/gp/product/B000CEO5T6/ref=as_li_ss_tl?ie=UTF8&psc=1&linkCode=sl1&tag=imddd-20&linkId=73d500d53bcced0c63a4e631de12290b&language=en_US

#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://www.amazon.com/gp/product/B01EC4G9JA/ref=as_li_ss_tl?ie=UTF8&psc=1&linkCode=sl1&tag=imddd-20&linkId=f9f4aee61114b21d3399ffb5bb9bb99a&language=en_US
Some 5/16 Gates fuel hose: Amazon.com - https://www.amazon.com/gp/product/B0058XDL0K/ref=as_li_ss_tl?ie=UTF8&psc=1&linkCode=sl1&tag=imddd-20&linkId=bada32111d1a5c41b2620d229dc72316&language=en_US
and 1/4 NPT to 5/16 fittings: Amazon.com - https://www.amazon.com/TUOREN-Barb-Brass-Fitting-Adapter/dp/B07RKM6VR8/ref=as_li_ss_tl?dchild=1&keywords=1/4+npt+5/16&qid=1595803669&sr=8-3&linkCode=sl1&tag=imddd-20&linkId=3e7d179c0e1dd36dc28df2c53b47d1a2&language=en_US


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

 

[FJRanger]

Unfortunately, I've only boiled gas on the California stuff.

 

[residualboulders]

FWIW - Returned to Canyonlands this week. Temps averaged 80-85 degrees. Both fuel tanks full at the beginning of the trail. No boiling issues over the two days. However, I would say I was likely in 4low for a longer length of time on Elephant hill (in the spring) when I did have boiling. Temps on that trail were the same.

So the insulation I added to the exhaust may have helped prevent the boiling, but it could also just be that I wasn't crawling in 4lo generating heat as long as I was on Elephant Hill. Go figure, I guess I'll just deal with it when it happens.

 

[Romer]

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.

how much of the exhaust did yopu wrap? Was it only near the tanks and fuel lines?

 

[Romer]

the company that makes the tape has several products. The Lava tape says 50% reduction, the shield product says 70% reduction

Exhaust Heat Shield, Automotive Insulation, Auto Heat Shield - https://www.heatshieldproducts.com/automotive/exhaust-heat-shield

Going to look more into the shield product. Anyone use that?

 

[linuxgod]

the company that makes the tape has several products. The Lava tape says 50% reduction, the shield product says 70% reduction

Exhaust Heat Shield, Automotive Insulation, Auto Heat Shield - https://www.heatshieldproducts.com/automotive/exhaust-heat-shield

Going to look more into the shield product. Anyone use that?

I’m not an expert but if you’re planning to use it around the exhaust I would only use it if there’s a specific spot that’s radiating a lot of heat onto a fuel line. The heat has to go somewhere and if it’s not radiating off the exhaust pipe it’s flowing downstream into a car or muffler or it’s radiating even further down the line.

Now if you’re wrapping the fuel line that’s a different story. I haven’t used this product specifically but I had an old mustang which used to kill starters because of the exhaust pipe location, and wrapping the starter in a similar heat shield blanket fixed the issue. So it does help block heat

 

[Romer]

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.

Curious what Charcoal canister you used, Stock (77740-60471)? Thinking my project over the winter is to go through insulating, but guessing my canister may be saturated by now. Wondering how challenging it is to drop the LRA aux tank and change the canister.

 

[TeCKis300]

Curious what Charcoal canister you used, Stock (77740-60471)? Thinking my project over the winter is to go through insulating, but guessing my canister may be saturated by now. Wondering how challenging it is to drop the LRA aux tank and change the canister.

Yup, confirmed that's the same part number. Write-up here if case you haven't come across it.

Anatomy of P0456 - Small Evap Leak

Recently have been getting CEL code P0456 - small evap leak. As the evap system self test is performed at night by the vehicle, usual symptom would be a nice greeting in the morning with flashing CEL, 4LO, TRAC, etc. And the inability to toggle 4LO, CDL, etc., if off-road camping. It...

forum.ih8mud.com

 

[JMK4]

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:

View attachment 3671316


View attachment 3671317

Did you end up doing this? If so, where did you install it and where did you plumb it?

 

[JPRS]

Unfortunately, I've only boiled gas on the California stuff.

And add Wyoming gas to the list as well (at least gas available around Cheyenne and Laramie, which may be the same as Colorado gas). I experienced the fuel fumes (but saw no evidence of boiling) on Wyoming gas around 10,500 feet using 4lo on a long climb up a somewhat steep and rocky trail. This was on a day when temps were in the 80s--at least that's what the temps were at the lower elevations (7,000 feet or so) at the base of the mountain. I have the steel catalytic converter protector plates installed on my 200, but otherwise stock skid plates.

 

[bentambling]

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:

View attachment 3671316


View attachment 3671317

Any update on these?

 

[TheGrrrrr]

Any update on these?

never got around to doing it. Still have the parts. Haven’t been wheeling the 200 much since I bought the 80. I still think it’s worth trying, so maybe after I sell the 80, I’ll tackle that project.

 

[linuxgod]

never got around to doing it. Still have the parts. Haven’t been wheeling the 200 much since I bought the 80. I still think it’s worth trying, so maybe after I sell the 80, I’ll tackle that project.

Sell the 80?!?!

 

[TheGrrrrr]

Sell the 80?!?!

I’d rather pull the race car with the 200, and while the 80 has achieved a state of humble perfection, it’s arguably too capable for the trails I run. Making things laughably easy was a great novelty for a while, but I just don’t push it to its limits.

 

[FJRanger]

Bringing this back to the top. We just made the trip from Southern California to western Colorado again and were smelling fumes as soon as we hit the desert. Baker and Grand Junction were 118/104 respectively when we passed through. When we pulled up to the property (sitting at 6200 feet), fuel vapor was visible exiting the fuel door and the fumes were overwhelming.

@TeCKis300 mentioned that the body lift, along with the other fixes, solved his boiling issues, and another gentleman in the LX570/200 North America FB group mentioned venting the hood. I requested that he post his results here and hope he does.

Has anyone else come up with any other fixes?

 

[JMK4]

Bringing this back to the top. We just made the trip from Southern California to western Colorado again and were smelling fumes as soon as we hit the desert. Baker and Grand Junction were 118/104 respectively when we passed through. When we pulled up to the property (sitting at 6200 feet), fuel vapor was visible exiting the fuel door and the fumes were overwhelming.

@TeCKis300 mentioned that the body lift, along with the other fixes, solved his boiling issues, and another gentleman in the LX570/200 North America FB group mentioned venting the hood. I requested that he post his results here and hope he does.

Has anyone else come up with any other fixes?

I’m going to be messing with mine more this summer. I lifted the rear of the hood about an inch to let air out, but it didn’t seem to help. Probably going to try venting the hood and possibly installing an oil cooler in the return line.

 

[FJRanger]

Have you tried any of the shielding?

 

[JMK4]

Have you tried any of the shielding?

Not yet

 

[JohnJB]

Bringing this back to the top. We just made the trip from Southern California to western Colorado again and were smelling fumes as soon as we hit the desert. Baker and Grand Junction were 118/104 respectively when we passed through. When we pulled up to the property (sitting at 6200 feet), fuel vapor was visible exiting the fuel door and the fumes were overwhelming.

@TeCKis300 mentioned that the body lift, along with the other fixes, solved his boiling issues, and another gentleman in the LX570/200 North America FB group mentioned venting the hood. I requested that he post his results here and hope he does.

Has anyone else come up with any other fixes?

Might wanna revisit the idea of it being solved.

Post in thread 'What have you done to your 200 Series this week?'

Aug 1, 2026

107°F ambient and crawling an arduous trail to 10kft.

Hot is an understatement... To be continued

• TeCKis300

• 
• 
• 

After 8ish years of 200 ownership, I’ve resigned myself to the idea this boiling is a feature, not a flaw. I’ve seen it occur on stocks trucks and modified trucks, I’ve seen it at lower elevations (sub 4k ft) and higher elevations, I’ve seen it on trucks that have attempted mitigation. On my personal truck, there are days it has occurred when I never would have suspected it and then not occurred on days I would have bet on it due to temps and/or elevation. Long way of saying good luck!

 

[TheGrrrrr]

Who needs the heat shield to actually separate the fuel return line from the catalytic converter?

Even the OEM skid would turn that area into a kiln, let alone a 1/4 inch slab of stainless steel.


This has to help a little bit.

 

[TeCKis300]

Just got back from extreme hot weather combined with extreme elevation trip. Yes, I did boil fuel. But so did the other ICE Jeep along with me at about the same point. The Rivian in the caravan did not have fuel to boil, but he used up 20% of his battery range in A/C just keeping batts from frying.

The yardstick for improvement is not that I boiled, rather when it boiled.

- I was at 9,000 ft elevation in the Sierras, having fueled up on 91 octane 50 miles earlier at 2,000ft in 107°F ambient heat, low range crawling technical rocks in some of the steepest longest climbs I've ever done. You can see from the post @JohnJB linked above in post #78, just how heat soaked the rig was (intake temps got to 203°F!)

- On a separate climb a couple days later, filled 91 octane from 4,000ft in 109°F, but in a longer smoother climb (still low range), going straight to 11,500ft over 2 hours, the fuel never boiled.

Putting some general numbers to this - fuel will boil in the following combination of elevation and temp. You can see at higher elevations, it really doesn't take much elevated temps in the fuel before it boils.

Altitude (Elevation)	Atmospheric Pressure	Winter Blend (High Volatility)	Summer Blend (Low Volatility)
Sea Level (0 ft)	14.7 psi (1.00 atm)	~100°F (38°C)	~130°F (54°C)
3,000 ft	13.2 psi (0.90 atm)	~94°F (34°C)	~123°F (51°C)
6,000 ft	11.8 psi (0.80 atm)	~88°F (31°C)	~115°F (46°C)
8,000 ft	11.0 psi (0.75 atm)	~84°F (29°C)	~110°F (43°C)
10,000 ft	10.1 psi (0.69 atm)	~80°F (27°C)	~105°F (41°C)
14,000 ft	8.6 psi (0.58 atm)	~72°F (22°C)	~95°F (35°C)

Fuel is not completely uniform and certain additional factors affect boiling point
- higher octane has a lower vapor pressure (boils later)
- more fuel has more mass to sink heat
- fuel purchased at high elevations will already have lower vapor point distillates so the delta of where fuel is bought versus where you're going can matter.

IMO, I've solved my boiling issues to the degree it's reasonable. I've previously boiled in Big Bear at only 6,000 ft at 95°F ambient.

Keys to solving the problem:
- Body lift helped hugely to minimizing trapped convective heat input to the tanks
- Insulation minimize radiant heat to the fuel system

If it does boil, DO NOT open the gas cap. It is keeping the fuel tank under pressure, so it does not boil more. Find a good point to stop, open the hood, and take a break. Mine stopped in about 10 minutes before I proceeded on.