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

[abuck99]

get a temp gun and do some work. It's not too hard. Everyone needs their own baseline. To gauge with.

I did a brief experiment a couple of months ago with IR temp gun, only measuring surface temps as I dont have an inline set up on the rail like you do. Not exact but it does help indicate cool and warm spots.

Ambient was 80F and after thirty minutes of city & hwy driving I measured the following:
FPR: 138F-outlet/inlet
Return Line: 128F
Fuel Filter: 120F
Pulse Damper: 139F

The variance is 40~60 degrees surface temp to ambient.

 

[jerryb]

Yup, what was I thinking, external is going to be different.
Still a good baseline for reference.

 

[silver02accord]

We were wheeling in Death Valley this weekend We had driven about 300 miles thus far on asphalt/Titus Canyon(faster speed off road).

We pulled off pavement and did about 20 to 25 minutes of low speed off road. We were coming from approximately an elevation of 250 feet. Temps were in the mid 60s, got up to elevation around 4500 feet. Stopped to take pics and I smelled gas, and saw it venting from gas cap. Visible gas vapors. I plugged in my carsoft and measured engine temp st 185 degrees.

I think my coolant system is in top shape-06' - Temps often 185 to 191.I've yet to install heat shield at fuel lines but I wanted to report this data point as ambient Temps and engine temp were not hot. Fuel filter, fuel pump replaced in last 6 months. Was running 87 octane.

 

[molonlabemike]

We had a 2006 with 120k on trail this weekend in SoCal that vapor locked. Cracked the fuel cap and no abnormalities so I cracked the fuel filter to vent which fixed it. Never had that happen in a 100 in 80 degrees near sea level

 

[Hugh Heifer]

We had a 2006 with 120k on trail this weekend in SoCal that vapor locked. Cracked the fuel cap and no abnormalities so I cracked the fuel filter to vent which fixed it. Never had that happen in a 100 in 80 degrees near sea level

Had it displayed any othe fuel related issues previously or was rhis a one off?

 

[neilsen100]

I have a '99 with 230k on the odometer. For years I've had a little bit of noise when removing the gas cap, regardless of temp and elevation, but never vapor lock, gas coming out or strong smell. This past summer I drove up the La Sals and had the first sensation of fuel smell and when I cracked the gas cap, visible fumes. The ambient temp was only 65 degrees but I had just driven through Moab where is was 103.

Talking with folks at HIH I was offered the theory that the charcoal canister is a filter that can become saturated over many years and then doesn't handle the fumes quite as well as it should. Based on this I chose to replace the charcoal canister and while doing so I weighed the old and new. This is hardly conclusive but I measured a 371 gram difference. That's more than 3/4 of a pound. Excited to get through the other work I'm doing right now and start driving again to see if this made a difference.

 

[hoser]

@neilsen100 It would be interesting to weigh the canister again after a few tanks of fuel.

 

[neilsen100]

good idea. That might take me three months to get through 3 tanks right now but I'll plan to do it.

 

[molonlabemike]

Had it displayed any othe fuel related issues previously or was rhis a one off?

It was a new purchase and he had the rig for 2 months so IDK

 

[hoser]

'06-'07 There have been quite a few mysterious stalling issues when hot.

 

[guardcompany]

'06-'07 There have been quite a few mysterious stalling issues when hot.

Agreed those years are specific to that problem. My 2004 has never staled or failed to start up. But of course I had the boiling gas issue bad.

 

[87warrior]

I have a '99 with 230k on the odometer. For years I've had a little bit of noise when removing the gas cap, regardless of temp and elevation, but never vapor lock, gas coming out or strong smell. This past summer I drove up the La Sals and had the first sensation of fuel smell and when I cracked the gas cap, visible fumes. The ambient temp was only 65 degrees but I had just driven through Moab where is was 103.

Talking with folks at HIH I was offered the theory that the charcoal canister is a filter that can become saturated over many years and then doesn't handle the fumes quite as well as it should. Based on this I chose to replace the charcoal canister and while doing so I weighed the old and new. This is hardly conclusive but I measured a 371 gram difference. That's more than 3/4 of a pound. Excited to get through the other work I'm doing right now and start driving again to see if this made a difference.
View attachment 2558287

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I can confirm replacing the charcoal canister on my 99 at 330k miles did not solve the excessive fuel vapor issue. As you also noticed, the new canister did feel substantially lighter than the old canister though.

 

[2001LC]

We were wheeling in Death Valley this weekend We had driven about 300 miles thus far on asphalt/Titus Canyon(faster speed off road).

We pulled off pavement and did about 20 to 25 minutes of low speed off road. We were coming from approximately an elevation of 250 feet. Temps were in the mid 60s, got up to elevation around 4500 feet. Stopped to take pics and I smelled gas, and saw it venting from gas cap. Visible gas vapors. I plugged in my carsoft and measured engine temp st 185 degrees.

I think my coolant system is in top shape-06' - Temps often 185 to 191.I've yet to install heat shield at fuel lines but I wanted to report this data point as ambient Temps and engine temp were not hot. Fuel filter, fuel pump replaced in last 6 months. Was running 87 octane.

It'd be interesting to see pictures if your undercarriage? To see what areas your "Full ASFIR Skid" covers, directs air flow or creates tunnels!

 

[Jfoofighter16]

I can confirm replacing the charcoal canister on my 99 at 330k miles did not solve the excessive fuel vapor issue. As you also noticed, the new canister did feel substantially lighter than the old canister though.

I'm in same boat, 03 and replaced CC around 190k and at 209k now. If I ever run ethanol and it's a hot day or I'm wheeling my gas will boil. I exclusively run ethanol free all year round now and have not had venting/boiling since. I know it's not a "fix" per se but it has resolved the issue from ever returning. Get used to maverik gas stations and pure-gas.org!

 

[87warrior]

I'm in same boat, 03 and replaced CC around 190k and at 209k now. If I ever run ethanol and it's a hot day or I'm wheeling my gas will boil. I exclusively run ethanol free all year round now and have not had venting/boiling since. I know it's not a "fix" per se but it has resolved the issue from ever returning. Get used to maverik gas stations and pure-gas.org!

My experience has been the same. I have been running [predominantly] E0 fuel for the last 4 years. If I do run corn infused fuel, venting and boiling are an issue.

 

[molonlabemike]

I’m gonna shield my fuel filter and fuel lines and see what that does. I think the files getting too hot and causing it to boil

 

[Joe422]

Only time I experienced fuel smell, pissing and venting was wheelin at altitude (Big Bear).
Smelt it... and had fuel leaking out the cap.. dribble marks. And even when stopped and shut down to vent... it would hiss for several minutes relieving tank pressure. Relatively hot day too. For the most part, I'm assuming I'm stuck w/ E10 in CA.

Wondering if Fuel coolers would be any help...maybe tapped into the return line?

 

[Jfoofighter16]

Only time I experienced fuel smell, pissing and venting was wheelin at altitude (Big Bear).
Smelt it... and had fuel leaking out the cap.. dribble marks. And even when stopped and shut down to vent... it would hiss for several minutes relieving tank pressure. Relatively hot day too. For the most part, I'm assuming I'm stuck w/ E10 in CA.

Wondering if Fuel coolers would be any help...maybe tapped into the return line?

I have seen an aftermarket product for this but never seen/heard of anyone trying on mud on their 100s.

If there was ever an aftermarket mod/thing to attempt messing with OEM environment to resolve I think it has to to with the pressure valve in the tank. Tanks with CC's have a pressure valve that will shut off if too much pressure for CC to handle and then it forces the "secondary system relief point" (in this case our gas caps) to vent....short story the gas cap venting is technically "intended" as the pressure needs to release somewhere. Theres a post/thread out there somewhere that explains all this.

Unfortunately, which is why our thread here exists, the secondary control here isnt safe, sucks to deal with when you are trying to wheel/have fun/camp, and you dont want to worry about blowing yourself/rig up in middle of nowhere!!

Also unfortunately, I dont know enough on how one could override that pressure valve (I could even be getting the terminology wrong on the valve name here) and force the CC to do "more work" and how viable or potentially even worse/more unsafe that may be. But it's something to think about for anyone who may know more on how to approach an aftermarket fix/mod like this.

I think the heat shields are a waste of time and this pressure valve is where the potential silver bullet fix may lie. My gut tells my the valve in overengineered by Toyota to probably shut off sooner than needed to be conservative, as is the case with most of the overbuilt parts on these LC's/LX's!

 

[Joe422]

Interesting point about pressure relief.
I have a couple 3 seater PWC's that have 16gal fuel tanks... and I usually store them completely empty, or completely full.
After noticing the tanks being pressurized over time, or when the skis get hot, I would check on them every few days to open the gas cap and relieve pressure. (these dont have any fancy valves to relieve pressure... and some are known for busting fuel tank seams)

Anyway, my fix for this was to acquire spare gas caps, and put a fitting w/ a 4ft clear hose (so i visually check too) ending with an aluminum one way check valve.
Now, in storage, I never have to worry about a pressurized tank, and if they vent, it would be very little by little. Point is to never let them got to higher pressures.
When I ride, I simply swap the vented gas caps for the original caps. Whether inside a garage, or outdoors, the vented fumes are never at a noticeable level.

-That being said, Im wondering of ways to maybe let the factory gas cap vent safely, (maybe manually controlled)... perhaps a manual valve? when and where we want it to vent.
So... we're not venting next to a campfire, or stove... etc.

-Or Maybe a gas cap w/ one way check valve could work at high altitudes? venting little by little and never getting to the higher pressures? You could even vent the cap, and maybe capture the fumes elsewhere? ... but I'm thinking the factory emmissions checks wont like that... maybe throw a code/CEL? Anyone ever drive w/ gas cap off and get a CEL?

-

 

[Jfoofighter16]

Interesting point about pressure relief.
I have a couple 3 seater PWC's that have 16gal fuel tanks... and I usually store them completely empty, or completely full.
After noticing the tanks being pressurized over time, or when the skis get hot, I would check on them every few days to open the gas cap and relieve pressure. (these dont have any fancy valves to relieve pressure... and some are known for busting fuel tank seams)

Anyway, my fix for this was to acquire spare gas caps, and put a fitting w/ a 4ft clear hose (so i visually check too) ending with an aluminum one way check valve.
Now, in storage, I never have to worry about a pressurized tank, and if they vent, it would be very little by little. Point is to never let them got to higher pressures.
When I ride, I simply swap the vented gas caps for the original caps. Whether inside a garage, or outdoors, the vented fumes are never at a noticeable level.

-That being said, Im wondering of ways to maybe let the factory gas cap vent safely, (maybe manually controlled)... perhaps a manual valve? when and where we want it to vent.
So... we're not venting next to a campfire, or stove... etc.

-Or Maybe a gas cap w/ one way check valve could work at high altitudes? venting little by little and never getting to the higher pressures? You could even vent the cap, and maybe capture the fumes elsewhere? ... but I'm thinking the factory emmissions checks wont like that... maybe throw a code/CEL? Anyone ever drive w/ gas cap off and get a CEL?

-

Yeah I think that would throw a code. I think i saw a post about someone drilling a hole in gas cap but that doesn't seem very "controlled". That's why i was thinking of getting to the valve inside the tank, replacing with newer/bigger valve that allows higher pressure or something. The idea being to direct more fumes/pressure at the CC that's supposed to take those fumes rather than venting from cap at all.