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]

Got more of the adhesive backed heat shielding and went back to give the LRA tank more thorough coverage. Those that have the LRA, this is critical as there wide swaths of metal in close proximity to the hot muffler ready to suck heat into the fuel system.. With more material, I covered the tank under the spare tire winch bracket and doubled up on portions closest to the piping/muffler. The arc is where my spare fits and that itself serves as a heatshield.

 

[kcjaz]

Got more of the adhesive backed heat shielding and went back to give the LRA tank more thorough coverage. Those that have the LRA, this is critical as there wide swaths of metal in close proximity to the hot muffler ready to suck heat into the fuel system.. With more material, I covered the tank under the spare tire winch bracket and doubled up on portions closest to the piping/muffler. The arc is where my spare fits and that itself serves as a heatshield.





View attachment 3405915

Good stuff. I have LRA and was thinking of trying to insulate the exhaust pipe itself (I’ve also removed my resonator). I think that would be effective in reducing heat heat soak in that it would put more heat out the exhaust pipe but I’m not sure if it’s a good idea from a corrosion of the exhaust perspective. May depend how well I should wrap the pipe and with what material.

 

[HSTexan]

I have only boiled twice--I have been lucky that neither have caused CEL's or limp mode. First was very minimal boil at LCDC this year that I didn't notice until I was getting gas on the drive back to TX and saw the residue. Second was just a couple weekends ago at a local offroad park at a measly 800ft of elevation. However, I had stupidly topped off with gas that morning and the temp outside was 108° by early afternoon. In that scenario I scared the crap out of someone following me who saw it trickling pretty seriously down my rear mud flap who thought I put a hole in my tank. Likely the combination of a super full tank (about 3/4 full or just over), extremely hot outside conditions, and slow crawling over rocks combined for the perfect storm. I keep a basic scan tool in my tailgate cubby in case I ever need to clear the code, but am very interested in long term results of shielding.

 

[TheGrrrrr]

Got more of the adhesive backed heat shielding and went back to give the LRA tank more thorough coverage. Those that have the LRA, this is critical as there wide swaths of metal in close proximity to the hot muffler ready to suck heat into the fuel system.. With more material, I covered the tank under the spare tire winch bracket and doubled up on portions closest to the piping/muffler. The arc is where my spare fits and that itself serves as a heatshield.





View attachment 3405915

Pretty sure that is the resonator not the muffler next to the LRA. From back to front its the resonator by the exhaust tip then the muffler then the cats.

 

[TheGrrrrr]

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.

Can confirm all of the above. This summer has been really bad for this on my rig. I'll be adding all of the shield suggested above, I'm going to drill a honeycomb of holes in the bud built skids to release the heat they are trapping and I'm still toying with the idea of a fuel cooler on the return line as a phase 2 effort if needed.

 

[TeCKis300]

Pretty sure that is the resonator not the muffler next to the LRA. From back to front its the resonator by the exhaust tip then the muffler then the cats.

Very possible and I was using the term generically. I recall someone cutting the middle unit open? Not sure what the axle back unit looks like internally.

 

[bloc]

FYI I installed thermocouples at the rail outlet (this one may need some adjustment), fuel tank inlet and outlet when I changed my pump. Things will be much cooler soon but I have a colorado trip coming up so should be able to get some useful numbers on how much heat is being added by the engine vs underbody vs tank.

 

[kcjaz]

FYI I installed thermocouples at the rail outlet (this one may need some adjustment), fuel tank inlet and outlet when I changed my pump. Things will be much cooler soon but I have a colorado trip coming up so should be able to get some useful numbers on how much heat is being added by the engine vs underbody vs tank.

Got any pics of your TC install?

 

[bloc]

Got any pics of your TC install?

The ones on the fuel tank inlet/outlet are nestled up on top of the tank, so pretty tough to get pictures. I just used aluminum HVAC tape to wrap the TC tip tight around the line, then ran the wires along the fuel lines to an area under the drivers seat where I have a hole in a plastic body plug.

For the rail outlet, my lead wasn’t long enough to cleanly get over to the passenger side rail outlet. The plastic line then runs back across the back of the engine and drops down into an adapter near the front left spring bucket.. where there is a short section of metal line before that goes into some rubber insulation. I used the same tape to attach the TC there at the metal line. My thinking here is that’s probably the hottest the fuel will be before leaving the engine bay.

Yes the exhaust manifold is nearby, but the fuel moving through the line should make sure the TC reflects the actual fuel temp.

Here’s a couple pics of my poor tape job of that one.. it’s pretty tough to get to. As I start collecting numbers if I get the feeling they aren’t accurate I’ll put in some more effort to clean it up.

 

[kcjaz]

The ones on the fuel tank inlet/outlet are nestled up on top of the tank, so pretty tough to get pictures. I just used aluminum HVAC tape to wrap the TC tip tight around the line, then ran the wires along the fuel lines to an area under the drivers seat where I have a hole in a plastic body plug.

For the rail outlet, my lead wasn’t long enough to cleanly get over to the passenger side rail outlet. The plastic line then runs back across the back of the engine and drops down into an adapter near the front left spring bucket.. where there is a short section of metal line before that goes into some rubber insulation. I used the same tape to attach the TC there at the metal line. My thinking here is that’s probably the hottest the fuel will be before leaving the engine bay.

Yes the exhaust manifold is nearby, but the fuel moving through the line should make sure the TC reflects the actual fuel temp.

Here’s a couple pics of my poor tape job of that one.. it’s pretty tough to get to. As I start collecting numbers if I get the feeling they aren’t accurate I’ll put in some more effort to clean it up.

View attachment 3427531

View attachment 3427532

so your tapping the TCs to the outside of the tubes and assuming that will be close to fluid temp? Shielding/insulating from manifold/engine bay heat is important. Maybe put a temporary TC in the vicinity to measure local ambient temp to compare to your fuel temp readings. Probably too evasive and risking leaks to do anything attempting to get the TC in the tube. It would be interesting to find something this.

 

[bloc]

so your tapping the TCs to the outside of the tubes and assuming that will be close to fluid temp?

Yes, I’m depending on the conduction of heat from fluid to line wall to TC being much more efficient than convection from the surrounding air. Or at least good enough for what we are trying to accomplish here.

There are certainly more accurate ways to get fluid temp but for a noninvasive method to determine whether the bulk of our thermal energy is coming from the fuel rails and/or the undercarriage, this should work well.

 

[isthatalexus]

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 all the 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 use case and mods that exacerbate heat into the fuel system, against mitigations sufficient to overcome those 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.




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

While more advanced and lab-not-required nano materials are slowly hitting the market, I think I'm going to modify your approach by using aerogel products in certain places. I found this for sale on the open market (NASA purchase order not required) and will look at ways to create fuel line sleves, and possibly deploying in bigger swatches where possible. If I find a self-adhering product, I will use that, e.g., to cover main and aux tanks, which should work since the really hot side is not on the adhesion side. The path to cool fuel is through minimally thermally conductive materials.

 

[TeCKis300]

While more advanced and lab-not-required nano materials are slowly hitting the market, I think I'm going to modify your approach by using aerogel products in certain places. I found this for sale on the open market (NASA purchase order not required) and will look at ways to create fuel line sleves, and possibly deploying in bigger swatches where possible. If I find a self-adhering product, I will use that, e.g., to cover main and aux tanks, which should work since the really hot side is not on the adhesion side. The path to cool fuel is through minimally thermally conductive materials.

That would be friggen awesome for this application and easier to apply if we could get ahold of this stuff. From a rust perspective, it's not great to use the stick on products as that creates lots of opportunity to trap moisture create corrosion. Let us know if you ever get your hands on any of this stuff to try.

 

[bloc]

That aerogel stuff could possibly even be put on the fuel rails?

As for logging temps.. I repeatedly space out on posting my findings.

Granted it was quite cool when I was in Colorado but for the one trail I was on.. it goes both ways. More heat is coming from under the hood or under the vehicle depending on running conditions.

At certain times the fuel returning to the tank was actually cooler than that leaving the engine bay. Other times, it was warmer.

Which means there were conditions that heat added under the hood was being shed under the vehicle before returning to the tank.. despite my E&E skids with cat guards. But not always.

I intend to do more logging when I head back up to colorado next summer, but probably won't have much data before then.


The one thing I'd want to add to the first few posts is some insulation to the fuel line that connects the rails together behind the intake manifold. Or that fluid/fluid heat exchanger posted elsewhere.

 

[isthatalexus]

That would be friggen awesome for this application and easier to apply if we could get ahold of this stuff. From a rust perspective, it's not great to use the stick on products as that creates lots of opportunity to trap moisture create corrosion. Let us know if you ever get your hands on any of this stuff to try.

To boot, the aerogel 'blanket' material is hydrophobic, so no water trapping. Yes, I may be an MSDS enjoyer.

(EDIT): thanks for the tip on adhesives and H2O issues; I will look at non-glue (e.g., wrap, tie) options,

 

[isthatalexus]

That aerogel stuff could possibly even be put on the fuel rails?

As for logging temps.. I repeatedly space out on posting my findings.

Granted it was quite cool when I was in Colorado but for the one trail I was on.. it goes both ways. More heat is coming from under the hood or under the vehicle depending on running conditions.

At certain times the fuel returning to the tank was actually cooler than that leaving the engine bay. Other times, it was warmer.

Which means there were conditions that heat added under the hood was being shed under the vehicle before returning to the tank.. despite my E&E skids with cat guards. But not always.

I intend to do more logging when I head back up to colorado next summer, but probably won't have much data before then.


The one thing I'd want to add to the first few posts is some insulation to the fuel line that connects the rails together behind the intake manifold. Or that fluid/fluid heat exchanger posted elsewhere.

I will investigate and document how the material is to work with. The MSDS call out the dust produced by handling/cutting the sheets, so not totally clear to me how small the strips for a fuel line warp can be while maintaining strucural integrity. I'm also going to call a buddy who works with high-pressure/high-heat steam applications about what fastening method (beyond steel zip ties) is useful for this material.

 

[BlackMammoth]

I have been using the phase change fuel cooler that came with the 200...

 

[isthatalexus]

I have been using the phase change fuel cooler that came with the 200...

Mr. BlaMamm, I like your 'does not elaborate further' approach due to its aesthetics, however I do humbly request elaboration. If we've been monkeying around with shields and thermometers, and dreaming of space-age thermal goos, and there's an OEM drop-in thingy out there to solve this issue, I think our Mudfriends and I would love to know more. (Too agressive for this particular case, but dropping my new coinage for such a scenario in the future: part number or it didn't happen)

 

[bloc]

Mr. BlaMamm, I like your 'does not elaborate further' approach due to its aesthetics, however I do humbly request elaboration. If we've been monkeying around with shields and thermometers, and dreaming of space-age thermal goos, and there's an OEM drop-in thingy out there to solve this issue, I think our Mudfriends and I would love to know more. (Too agressive for this particular case, but dropping my new coinage for such a scenario in the future: part number or it didn't happen)

I took it to mean he’s been getting fuel boiling.. which cools it.

 

[isthatalexus]

I took it to mean he’s been getting fuel boiling.. which cools it.

...is this me?