Gas puked out of filler cap and major vapor pressure

[87warrior]

I had a shocking problem with the 100 this Father's day weekend out in Colorado. When climbing Hayden Pass I started to smell terrible gas fumes at about 10,000' and assumed it was the side-by-side ahead of me. Then fuel puked out of the sealed gas cap, yes it was properly secured. You can see the route the gas took to escape here:

I stopped at the top of this pass, a mere 10,700', and could see fuel vapor roaring out of my fuel cap. I cracked open the cap and noticed an immense pressure release. After 15 minutes of pressure relief, I went ahead and pulled the cap and it continued vent for another 5 minutes or so. The charcoal canister under the hood was also making a popping or groaning noise. I had filled the tank to the first click then drove 35 miles to the trailhead, so it had to be down a couple of gallons.

It was hot this past weekend. 100 degrees. Yes, it was 100 degrees above 10,000'. I had the AC running full blast and the transmission was locked in 1st crawling up in Lo. The motor never heated up and there was not much stress on the drivetrain. I have no doubt heat and air pressure were contributors to the problem, but there must be an underlying problem that allowed the heat and altitude to have such an effect. The day before I drove up as far as I could on Mount Antero, about 12,500' before the snow stopped me. It was in the 80's and I had no issues.

I will disclose that during the drive to Colorado, my CEL illuminated between Goodland, KS and Limon, CO then turn itself off. The drive home was uneventful. No CEL and gas stayed in the tank. I pulled the codes when I returned home and had 4 active faults. To my surprise, nothing related to the Evap system was stored.
P0100: Mass or Volume Air Flow Circuit
P0101: Mass or Volume Air Flow Circuit Range/Performance Problem
P0110: Intake Air Temperature Circuit
P1121: [Toyota] Accelerator Pedal Position Sensor Range/Performance Problem.

The codes are pretty straightforward and should be easy to remedy with exception of the cost for the APPS

I've searched for help but have come up mostly empty handed in regards to the fuel puking out the filler. I haven't found any report of someone actually losing fuel out of a closed cap or having the amount of vapor build up that I had. I did see a few people have had excessive vapor build up and said it could be the charcoal canister but dismissed the problem as rare and not a concern. The charcoal canister was also mentioned as the cause for the slight pressure released when removing the fuel cap most 100's experience. I'd like to do some more research on this as the charcoal canister is $$$.

What could be wrong? This is a stock 100 series. I've never has this happen with any vehicle before, so I don't even know where to start. Am I on the right track looking towards the Charcoal Canister?

 

[re_guderian]

Pretty normal for hot and big elevation changes. Buy a new cap, but it'll probably happen again in similar circumstances. Lots of threads on it.

 

[Dzrtcrzr]

Has this happened to anyone else? Fuel pressure

 

[87warrior]

Yes there are several threads, but no answers, rhymes or reasons to be found. Having been visiting the Rockies for most of life I have a hard time believing this issue is one a 100 series owner must accept as 'normal'. This is unacceptable. The fumes inside the cab were atrocious and nauseating. My passenger bailed on me at the top of the pass to ride down in a Jeep that had no problem. The elevation change from the town of Salida and the top of Hayden Pass is about 3,700 feet and it took about 3 hours to make the slow climb (east to west). Any of the major highway passes in CO have a much faster climb rate than I did on the trail.

Since the ECU didn't mind the charcoal canister failure, I wonder if one can modify the stock unit to bleed pressure faster or if an aftermarket/other vehicle OEM canister that bleeds faster could be found.

I am set to take the 100 back to Colorado for a week in August. I must find some sort of solution to this problem. I'd rather not take my Jeep this year. I bought the 100 expecting it to take the Jeep's place!

 

[Get outside]

I've learned my lesson! If I'm on high elevation I fill my gas tank 3/4 max!

 

[socalmtbiker]

I just had this happen to me as well with similar conditions. I had no check engine lights or codes pop up. Luckily for me, I just recently purchased the car from Carmax (I hate them, but they were the only place that had a 100series. I have to say they fixed all the problems I've had with no questions) and took it back to them to assess. With the info here, I asked them to check several related valves and the charcoal canister. They changed the the CC and found nothing else was wrong but sent the rig to the lexus dealer to have them double check if anything was overlooked. The rig is still at the lexus dealer but I should get word today.

 

[slimbuddha]

I had it happen once in high-temperature, and around 5k elevation, and I received a CEL code. I cleared the code, and after it cooled down and tank emptied, it never happened again.

 

[savirc]

This happened to me literally two weeks ago at Big Bend on Black Gap road same conditions, change in altitude, 110 degrees topped off on gas. The gas fumes were so hot and pressurized when I opened the lid slowly it actually removed the paint from inside the lid. Have not topped the tank and no more problems, seems like a crazy problem if you ask me, the canister should be able to handle altitude/pressure changes seems like a design flaw. Since I've looking at "venting" gas caps, but this may only lead to ECU codes later.

 

[slimbuddha]

Has anyone ever just replaced the charcoal canister after having the problem? Maybe it's just built up crud/partially clogged, and doesn't work as efficiently. I know my Big Bertha is already 16 years old now.

Check this out:
Charcoal canister: maintenance and repair | Mechanical /Maintenance Forum | Bob Is The Oil Guy

 

[socalmtbiker]

I just picked up my rig up. Lexus has no explanation and did not find any faulty valves. The CC was replaced. I know this a 11 yr old rig but I think this is not normal operation. I believe that because people who purchase this rig new are not likely to go wheeling as its intended purpose that this issue never really became recognized as a possible TSB. This is definitely a safety concern for myself since I intend to overland with my kids in tow.....

 

[abuck99]

When the EVAP system is working correctly, this should't happen. Something in the system is not functioning correctly to return the excess pressure back to the manifold; a malfunctioning gas cap, a kinked, blocked or hardened vacuum line, a malfunctioning valve or sensor etc.

It would be interesting to know what model years experience this problem; is it an vehicle age issue or model year specific issue.

 

[socalmtbiker]

When the EVAP system is working correctly, this should't happen. Something in the system is not functioning correctly to return the excess pressure back to the manifold; a malfunctioning gas cap, a kinked, blocked or hardened vacuum line, a malfunctioning valve or sensor etc.

It would be interesting to know what model years experience this problem; is it an vehicle age issue or model year specific issue.

I have a 2005 lx 470- everything you mentioned was checked at the Lexus dealership after being checked at the CarMax mechanic (where they replaced the CC). Nothing came back.

 

[nakman]

It's the ethanol in the gas. Coincidence, this just came up on a thread on our club forum... you'll recognize half the participants. Help!!! Gas tank back pressure!???!?? - Rising Sun Member Forums

Consensus there is it's normal, don't top off or over fill, and venting it actually makes the condition worse.

 

[abuck99]

With out knowing what inspection/maint protocol the dealer used to check the EVAP system, its hard to say how thorough they were. Probably the required minimum, which may not have repeated the conditions under which you experienced your problem.

But I think the solution is complicated- is it a design limitation or a failure somewhere in the system? There are so many variables involved that can impact tank vapor venting. Altitude- Ambient Temperature -Fuel Tank Temperature -Vehicle age -Fuel Properties (summer blend, winter blend, regional additives, oxygenated fuels etc) -Ethanol content -Reid Vapor Pressure (RVP) of the fuel- and of course Malfunctioning components. Modding the EVAP system seems problematic on many levels since its tied into the ECU.

Smoke test is a good method to indicate any EVAP system failure points.

 

[suprarx7nut]

This is awesome info - nakman, thanks!

Great Dissertation on the topic (more or less) from Rising Sun here: http://scholarworks.umass.edu/cgi/viewcontent.cgi?article=1341&context=open_access_dissertations

I'll have to keep that in mind for HIH6 this year as I climb in elevation.

I wonder if this phenomenon was considered when our regulators pushed E10. Apparently 95% of US gasoline is E10, with a declining rate of E0 (ethanol free) usage.

Almost all U.S. gasoline is blended with 10% ethanol - Today in Energy - U.S. Energy Information Administration (EIA)

If this happens to these 100's so violently under certain conditions I wonder how much vapor is released from other models during normal usage. At some point the "renewable" push becomes a liability if it creates spewing gasoline fountains out of otherwise functional gasoline systems.

 

[abuck99]

The ethanol data goes back pretty far 20-30 + years so I would believe they are fully aware of the blending percentages and effects. The regulators dont give a damn about the negative effects, they just want the money the ethanol lobby provides. As a matter of fact the EPA is pushing the blend wall again, working very hard to get 15% ethanol blending implemented and pushing hundreds of millions of additional gallons of ethanol onto the market. There is a vote coming soon, and if you care about it let your representative know how you feel here:

From the looks of it from 2004 forward are the most stringent EVAP controls with the introduction of the Tier 2 LEV II standards. So those of us with 2004+ vehicles will probably be affected by the condition more than the older 100's.

With so few 100's produced compared to all other Toyota models and a handful of those actually having the issue we probably dont have much chance Toyota will do anything. But maybe filing a complaint with NTSB will get the ball rolling.

 

[smakee]

Yep, happened to me heading up to Estes Park this past weekend pulling the popup. I started the thread on Rising Sun because it freaked me out. First time it ever happened to me.

 

[TeCKis300]

Common or not, this is not a safe situation and should be avoided if at all possible. Gas in its liquid form will not light as readily, but in vapor form like this...kaboom! Especially with the hot exhaust and exhaust components underneath.

Sounds like there's some good strategies to avoid this. No more than 3/4 tank of gas when doing this type of wheeling. And don't vent the cap! It will only encourage the fuel to boil more. Same idea with the coolant system...we all know not to vent the cap when the system is hot!

 

[87warrior]

What a great discussion. Thanks!

It's unfortunate we cannot beat the ethanol craze or regulations. I do wonder if an additive could reduce the effects of the ethanol in this situation. I don't know enough on the subject to even speculate, so maybe someone else can chime in.

Can someone who has an early 100 with the charcoal canister under the hood do a brief test for me? I didn't drive the 100 today so I could check out the Evap system after work. Although I could not find anything out of sorts, I did notice the purge valve on top of the charcoal canister got hot enough to be painful when touched after 10 minutes of idling with the hood up. It would be great if folks who have had the puking gas/vapors could check their 100's purge valve gets extremely hot in a short amount of time. Those who have never had the issue should report their findings as well.

I also found it interesting that unplugging the purge valve on the charcoal cansister and/or the vapor pressure sensor next to it did not trigger any faults. I was also unable to view the evap vapor pressure reading in Torque as it wasn't reporting through the ECU.

 

[socalmtbiker]

Common or not, this is not a safe situation and should be avoided if at all possible. Gas in its liquid form will not light as readily, but in vapor form like this...kaboom! Especially with the hot exhaust and exhaust components underneath.

Sounds like there's some good strategies to avoid this. No more than 3/4 tank of gas when doing this type of wheeling. And don't vent the cap! It will only encourage the fuel to boil more. Same idea with the coolant system...we all know not to vent the cap when the system is hot!

Well, not that it matters but I sent an email out to Lexus about my concerns. I had a reply that I will be assigned a case manager. I uploaded my photos and provided links to serveral threads on this problem. I mentioned that this was not limited to the lx but any of the 100series.

I for one, can't accept it as "normal" for gas to spurt got and not had in having the ability to fill up a tank more than 3/4 full. Will they do anything? I'm not sure, but they won't be able to fix anything if they don't know that the problem even exits.

Anyone that cares enough should send an email to lexus/toyota. I just went on Lexus.com and clicked my way to contact.