Gas tank building excessive pressure & fuel smell. Dangerous for sure! Why does this happen? (1 Viewer)

[2001LC]

Have you ever thought about testing a 160* thermostat just to see what happens? The part is relatively inexpensive at about $35 and it would be interesting to see if it might help to keep the ECT temps to something that works better with the fuel temps.

I haven't ever had my 42 gallon tank boil over, but I have gotten some excessive venting before when I was at elevation in the San Juans. It was boiling, but just slightly. It tends to be the San Juans causing most of the issues because of all of the high mountain passes. Most of the trail leaders will warn people to just leave their trucks running when we stop for a few minutes to avoid a no start situation due to fuel problems. If I remember correctly, it is the 06-07 that seem to have the biggest issues with not restarting due to fuel problems at elevation.

It might also be worth it to pop into the Colorado Plans Silverton thread and see if anyone had any issues while it is fresh on their minds. Colorado plans Silverton July 22nd-26th

The thought crossed my mind, after learning you're running a 160 thermostat. But you've a fuel/air/spark that is different than stock. In your case it makes sense, to run cooler. For one; Boost is safer with a loose engine, according to a machine shop I've been speaking with. A hot engine runs tighter. Additionally your TRD package likely runs richer to accommodate the forced air. I suspect you've a tweek to the ECU, to run rich. But really, TRD package and boost is above my pay grade.

I do feel, your's (a heavy 99 with a "few miles") is additional anecdotal evidence, running cooler ECT is key. As you're not experaning fuel boiling pressure issues.

 

[2001LC]

A few early morning thoughts, with my coffee.

Getting to normal operating ECT is my first goal and of key importance.

But I'm now wondering if different years may have variation in what's normal running ECT.

That the 06-07 VVT, may be a little hotter running. 03-05 may also have a slight variation in normal operating temp being little hotter vs 98-02. Although all stock 4.7 2UZ-fe have same temp thermostat. It's been noted in mud, we've differences in radiator, that someone said is fin pitch IDK. I do know we've a different fan blade and clutch in the VVT. The clutch fan is ~11mm thicker and fan has design variation, why IDK. I assumed for great fuel efficiency. I also note difference in long term fuel trims. 98-02 tend to run closer to 2.5%, 06-07 closer to 5%

I've a few logs of 06-07, that indicate they run little hotter. Unfortunately I've only a few logs I emailed myself. With these logs, I was interest in other data for other reasons. I sometimes ran the logs as I did high RPM runs, to burn out carbon & fuel gunk from cylinder heads and cook the CATs, A/F & O2 sensors. Intentionally getting CATs as hot as I could. I'd run near 5K RPM for 5 to 7 minutes. Like turning and oven to clean. So there not the best logs, for what I'm looking at today. Additional most are before I really got serious about cleaning radiators of debis.

One set of logs are on Merlot (07LC 64K), before and after belly pan and full skids. It shows running little hotter ECT after bell pan installed. I didn't clean radiator fins. Perhaps I should have, even though, it only had 64K on the clock. It came from South TX rural area. Those areas get swarms of insect, which covering front end moving down the road (dead bug is a good bug...lol, or is it). That would have some radiator clogging, I'd not considered at the time.

I've noticed with clogged radiator fins. Is that ECT not only runs hotter. But raises faster and higher. This is compounded with both A/C running, and most notable at slow speeds or stopped with high OAT.

We may also have a feedback loop. In that I mean, as we run hotter, the CATs and engine compartment heat. This is heating fuel lines/fuel. As fuel heats, the molecules expand. This would likely reduce fuel in the mixture, leaning fuel air mixture. Lean fuel mixture raises cylinder head temp which heat CATs. Then ECT goes up. The EUC would than work to richen the mixture.

Additionally a weak fuel pump would lean then mixture. We've a known issue with VVT fuel pump. They tend to have low fuel follow at low speed. That as they get hot, the resistance in pump motor raises to point it slows and we stall, as flow/pressure to fuel rails drops. This has been wrongly (IMHO) call vapor lock. It happens most often in very hot areas like NV and AZ or on mtn passes on hot days here in Colorado.

To make the whole issue more complicated. We possibly 3 variation in EVAP systems. The biggest change was movement of CC to rear in 03. In those with rear CC, the fuel boiling may be damaging the CC or it's pre filter. I say this as we know topping fuel tank does damage CC, as it get raw fuel into the CC. Fuel boiling to point it comes out gas fill neck, would do much the same.

In 98-02 we've the fuel tank cut off valve. That may be sticking, due to gunk build up. I'm not sure, but it appears the valve connects to line thats is part of vacuum pull on tank. If the valve stuck in shut off, could it then have effect of increase fuel tank pressure.

So no one cure fits all. But ECT and a well tuned engine is key, to all as a starting point.

 

[2001LC]

IDK- maybe a small increase in fuel econ.(1mpg) The fuel vapor issue this year was less than previous years- id had a good deal of vapor staining on near the fuel door in past years at Silverton but none this year. Differences; substantially cooler ambient temps, more rain, using lower octane fuel, fan clutch mod, some new vacuum lines. Random.

Chuck at FIS here in Denver, was first to clue me in on FPR and MPG improvement. He'd said we see greatest benefit in the summer. Seems you're seeing that in .1mpg. Your fan clutch mod and radiator fin clean surly didn't hurt ECT either.

 

[2001LC]

I noticed that Rock Auto has Aisin fan clutches for $73 if you still need one.

RA will not delivery to us in our zip code. Tax laws BS.

 

[hoser]

Hmm why so certain? Your photo is looking directly at a SEAM in the plastic. Have you aged it for 13 years and gave it plenty of use? How does the plastic ring seal against the metal tube? No possible way? I'm looking at one possible way...

Also this neck is not the same as the neck on my 2007 which has two vent tubes, one from the tank and one from the CC.

The plastic bushing rotates semi-freely. Go spin yours. There is no seal. As part of the LRA aux tank install (98-07), you cut the seam on the OE bushing and install onto LRA filler neck. Notice the cut at the 12 o'clock position?

Your rubber glove test is flawed. The gas cap seals against the metal filler tube, not the plastic bushing.

 

[gungriffin]

You can treat the cause, or you can just look awesome and cure the symptoms... I will be installing these next month when the combo I want is back in stock. I don't trust my no boil luck to hold out when I am on the trail.

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[90WT]

You can treat the cause, or you can just look awesome and cure the symptoms... I will be installing these next month when the combo I want is back in stock. I don't trust my no boil luck to hold out when I am on the trail.

Large SMOOTH-BORDER Powder-Coated Semi-Gloss Black Hi-Flow™ - Hood Louvers | RunCool | Hood Vents For Your Vehicle -

RunCool is your source for Hood Louvers which Cool Your Engine by allowing Heat to Escape. Run Cool Hood Louvers built with Quality in Mind.

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Those Louvers are sweeeeet! Would love to see installed pic of those!

Have been following the thread. Installed Ultra Guage about a month ago when we got a new trailer. My rig runs at 195.8 deg nearly all the time except when towing my 3200# trailer when it can shoot up as high as 220 deg on the mountain passes up here. First time ever experiencing the gas cap fumes two weeks ago when pulling that trailer on dirt roads, 30 mph for about an hour, at 80 degrees OAT, at around 5000 ft elevation. The Ultra Gauge beeped and threw me a P0441 code. Opened up the gas cap and watched fumes escape for 30 minutes or so. Made for an interesting camp trip. Replaced two year old gas cap with new gas cap. Waiting to see if there is a magic bullet that plops out of this thread.

 

[2001LC]

personally I'd want as much fuel returning to the tank as possible while maintaining spec pressure and leak down.
The older the spring is, the more returns to the tank. The newer the spring is, the more is retained in the rails - the normally considered hot part of the system.
One air bubble being pushed down the return line, on either side of the regulator, or between the damper and the regulator dooms everything. That is what you hear with the engine off. The only thing I think has changed is the property of the fuel.


isn't it known that a lower temp thermostat will just allow it to start the overheating process faster?
if one unit must have 10mm of lift at a certain temp and another must have 10mm of lift at a lower temp than the first, will they reach an overheated temp at the same time or will one be faster than the other? all else equal, no change in volume through the orifice.

for the life of me I cannot see how normal coolant temps have anything do do with fuel boiling.

I can say without a doubt. In the op #1 & #2 the 99LC ECT was running hot. It would rapidly change as I stop at a light. On the HWY it ran coolest, but still hot. It also had some typical and non typical vacuum leaks for age, I corrected. That when serviced coolant system and I corrected all vacuum leaks, but failed to thoroughly clean radiator. Fuel boiled as ECT went up. I then really cleaned the radiator well, the second time. ECT came down and stable. Now no fuel boiling/pressure issues.

In @CUBuffs', 07 which a is very nice clean well maintain rig. ECT was jumping around rapidly, to over 200F. I noticed something strange also; As I was looking at engine just after it been driven. I could not put my hands on the sides upper radiator support, as they were to hot. I've never noticed that before. I lean on those all the time.

The radiator looks great and drain just find as did block drains. But I'm now wondering, if we may have a blockage. Perhaps some old heater Tee plastic, block radiator plumbing. Both HVAC heaters are blowing hot. So if blockage, would seems be in the radiator. Not sure how I'd check for this.

 

[Eyedaho]

I can say without a doubt. In the op #1 & #2 the 99LC ECT was running hot. It would rapidly change as I stop at a light. On the HWY it ran coolest, but still hot. It also had some typical and non typical vacuum leaks for age, I corrected. That when serviced coolant system and I corrected all vacuum leaks, but failed to thoroughly clean radiator. Fuel boiled as ECT went up. I then really cleaned the radiator well, the second time. ECT came down and stable. Now no fuel boiling/pressure issues.

In @CUBuffs', 07 which a is very nice clean well maintain rig. ECT was jumping around rapidly, to over 200F. I noticed something strange also; As I was looking at engine just after it been driven. I could not put my hands on the sides upper radiator support, as they were to hot. I've never noticed that before. I lean on those all the time.

The radiator looks great and drain just find as did block drains. But I'm now wondering, if we may have a blockage. Perhaps some old heater Tee plastic, block radiator plumbing. Both HVAC heaters are blowing hot. So if blockage, would seems be in the radiator. Not sure how I'd check for this.

Can't you just disconnect the upper and lower radiator hoses and blast a garden hose in opposite direction of normal flow? If there's a piece of plastic sitting in the radiator, I would expect that to flush it out into the ground.

 

[2001LC]

Can't you just disconnect the upper and lower radiator hoses and blast a garden hose in opposite direction of normal flow? If there's a piece of plastic sitting in the radiator, I would expect that to flush it out into the ground.

Worth a try. THX. Then, I'd need to get every drop of tap water out.

 

[J1000]

The plastic bushing rotates semi-freely. Go spin yours. There is no seal. As part of the LRA aux tank install (98-07), you cut the seam on the OE bushing and install onto LRA filler neck. Notice the cut at the 12 o'clock position?

Again, mine is different to yours. Mine does not rotate. As you can see in my photo there is a 2nd vent tube that is fully encapsulated in plastic keeping it from moving.

Your rubber glove test is flawed. The gas cap seals against the metal filler tube, not the plastic bushing.

Yes, but in combination with many other tests it gives useful info. I did lots of testing including with a brand new Lexus gas gap, a brand new generic gas cap, physically blocking the filler neck with a rubber cone plug like this: Uniweld 40050 Rubber Plug Adaptor, 1/2-Inch - Air Tool Fittings - Amazon.com etc

 

[Austin Hot Shoe]

I don't believe it is a defect in design, its a defect in the fuel for the vehicle design. The 100 was designed for gasoline, not ethanol blends with higher evaporation.
In the desire to use more renewable fuels, politicians and the EPA decided that corner cases like EVAP overload at high altitude or very hot ambient temperatures would be sacrificed, the data they collected below shows they knew there was an issue.

I have done multiple trips comparing non-ethanol vs ethanol E10 and never have an issue with non-ethanol.
I think the worst case testing ground is the San Juan Mts. due altitude and availability of non-ethanol.
You have several high passes with one over 13,000 and temperature can get in the 80s
My first trip there in 2017 for HIHs running E10, I had high gas tank pressure and some gas blow by when opening the filler on the high passes. Since it is a 100 series event there was a lot of venting going on. We were told it was common problem and to not fill tanks above half full, which I did for the rest of the event. Still had high pressure to vent but no gas blow by.
In 2018 the first day had E10 from trip in, and had high tank pressure when venting on the high passes. Next day filled tank to little over half with non-ethanol in Silverton, no pressure on vent on high passes. So decided to go for broke third day filled tank to the top (FULL) with non-ethanol, and headed to top of Black Bear pass (12,840ft) at the pass, opened the filler and no pressure, none!!! My friend in an 80 series found the same results.
In 2019 only used non-ethanol and filled up every time and no pressure on any of the passes including Imogene Pass at 13,114ft. On this trip two friends in 80 series and two friends in 100 series also found no tank pressure on high passes using non-ethanol.
These trips have all been the first week of August.
By the way this is the original factory evaporative emission control (EVAP) system, no changes or part replacement.

Ethanol blends are neither bad nor good just need to be used in systems designed for them. Since the majority of our fuel is now E10 I think it is good that a number of you are testing modifications to improve how our vehicles deal with E10. Keep up the good work.

Scientific data below.
While ethanol does boil at higher temperature (i.e. has lower vapor pressure) than gasoline, blends have a non-linear relationship.
For blends below about 40% ethanol the vapor pressure can be over 10% higher than gasoline. In order to market E10 the EPA granted a waiver on vapor pressure requirements for E10 as it could not meet the EPA requirement on gasoline.

The following graph is from the National Renewable Energy Laboratory which is part of the US DOE.

From the NREL report.
However, when blended into gasoline at relatively low concentrations the more numerous gasoline molecules disrupt the attractive forces between ethanol molecules and allow the ethanol to readily evaporate, raising the vapor pressure of the blend.

@Skidoo I 100% agree, went to Silverton last week and ran all of the high passes.......found non ethanol gas in town and no venting at all!

 

[Catskills]

@Onur and I have been experimenting with non-ethanol. Two days ago I filled up the tank with non-ethanol but the rest of the tank was half-full with ethanol. Still had issues. In fact it very nearly didn't start yesterday when I shut it off after running it for an hour.

100 degrees here in Grand Junction and towing my raft.

Then this morning on a quarter tank of the mix I filled it up again with non.

Again towing the raft, this time two hours from GJ to the Colorado down by Moab. About 100 degrees again. No fumes whatsoever. I am thrilled! This has been an issue for my truck since 2016 when I drove it to Montana, and husband has replaced many components that could have contributed to this issue.

Headed to Cedar Mesa in a few days where I'm sure this would have been an issue, and Ouray next weekend. So happy to have an easy fix for this, especially since it doesn't impact the truck at all on the East.

 

[2001LC]

Seems to be a lot of anecdotal and scientific evidence, that ethanol blend is a major factor.

Still, seems most handle ethanol blend well enough.
Otherwise if nothing else, wouldn't we see every rig at HIH each year that's not using non ethanol fuel and or heat shields, boiling fuel?
Wouldn't statements about fumes and gas caps blowing fuel, domate the HIH thread.

But still it seems, that if all mechanical basics inline. The system can handle the blended fuel. Use unblended and system handles better. So not a design flaw. But perhaps the EVAP system, could have been more robust to handle the blend fuels better. Could that be some of the reasons, behind design changes through the years?

 

[DTC72]

I ran most of the major trails and passes in Silverton for the first time and thought I’d share. A quick recap so you don’t need to go black on the thread:
- 2006 LC100
- had 5 previous vapor locks in high heat but moderate elevations
- never had any gas boil or spit out but often get gas smell in high heat
- replaced gas cap, fuel pump, fuel filter, evap canister since mine was an early 2006 with a VIN that had a recall but only if you threw three specific codes which mine never did

The first day we ran several easy gulches and my tank was 3/4 full of 10% ethanol gas. Not too far in my truck there a PO441 Code Evap System Incorrect Purge Flow. First time ever for that code for me. I did smell faint gas smell but no boil and no spit out. I cleared the code and ran the trails the rest of the day with no issue.

For the rest of the week I filled up to 3/4 tank with Ethanol free gas. Harder and higher trails also. No additional issues, gas smell, codes, nothing. The last day I filled up a full tank By accident and we ran Mineral Creek and a couple others. Again no issues.

Home in Las Vegas and it has been 106 plus. Gas smell in garage after a couple of short errands. Of course full tank with 10% Ethanol gas. The annoying saga continues.

 

[Skidoo]

Seems to be a lot of anecdotal and scientific evidence, that ethanol blend is a major factor.

Still, seems most handle ethanol blend well enough.
Otherwise if nothing else, wouldn't we see every rig at HIH each year that's not using non ethanol fuel and or heat shields, boiling fuel?
Wouldn't statements about fumes and gas caps blowing fuel, domate the HIH thread.

But still it seems, that if all mechanical basics inline. The system can handle the blended fuel. Use unblended and system handles better. So not a design flaw. But perhaps the EVAP system, could have been more robust to handle the blend fuels better. Could that be some of the reasons, behind design changes through the years?

Was at HIH a few years back and the group stopped at one of the high viewpoints. Everyone thought their 100 was doing fine. One guy heard noise from his gas tank and loosened his cap and pressure and gas came out. Trail leader said that was normal, so others started loosening their caps and soon I was in the middle of at least six 100s venting a lot of pressure including mine (had E10 in tank). I don't think its reported much from HIH because its "normal" and for them it only happens there, many of the folks attending are from the lowlands and HIH is their offroading for the year. For the following years I used non-ethanol and had no venting issues.

 

[Jono85]

This happened to me last summer at 40+ degrees C and Barrington tops altitudes. Never had it happen before. Turns out i had filled with E10. Has not happened since on normal fuel. Didn't seem to cause any problems just noticed the fuel vapour smell and decided to open the fuel cap.

 

[Skidoo]

This happened to me last summer at 40+ degrees C and Barrington tops altitudes. Never had it happen before. Turns out i had filled with E10. Has not happened since on normal fuel. Didn't seem to cause any problems just noticed the fuel vapour smell and decided to open the fuel cap.

Down Under is most of your gas non-ethanol or have they legislated that most all gas is E10 like the States?
That hot (over 100F) and close to 5,000ft with E10 would expect that.

 

[molonlabemike]

04 lx having this issue. Over this weekend we attempted to go to a higher elevation lake but noticed we had fuel pouring out the gas cap and the gas tank boiling as well. Was a full tank of gas, 100 degrees out and 9k of elevation. I just replaced my radiator with a brand new TYC (sp?) (which happens to have a pin hole leak) and I did notice that the floor is getting pretty hot. I’m thinking I might have a cat getting clogged or something. I plan to shield the fuel lines from the cats and possibly replace them to see if this solves my issue.

 

[suprarx7nut]

Seems to be a lot of anecdotal and scientific evidence, that ethanol blend is a major factor.

Still, seems most handle ethanol blend well enough.
Otherwise if nothing else, wouldn't we see every rig at HIH each year that's not using non ethanol fuel and or heat shields, boiling fuel?
Wouldn't statements about fumes and gas caps blowing fuel, domate the HIH thread.

But still it seems, that if all mechanical basics inline. The system can handle the blended fuel. Use unblended and system handles better. So not a design flaw. But perhaps the EVAP system, could have been more robust to handle the blend fuels better. Could that be some of the reasons, behind design changes through the years?

FWIW, I think the E10 nonsense mandates occurred after the design period even for the late 100 series models was complete. I think regulation took effect 2010, but some warning was given. If the rig runs well on non-ethanol gasoline, but fails completely on E10, I put the blame squarely on the shoulders of legislators.