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

[Brandon Ryder]

IMO, absolutely a hazard and should not be opened. Let the safety relief do it's thing (IE keep it closed).

I understand the urge to vent it quickly, but best to just let it vent and if you've got liquid misting out prepare any onboard extinguisher you have.

Mine vents under the hood from the Canister if i don't vent it from the gas cap. And it takes forever. When this does happen i have to make a decision which is more dangerous. We really need to find the correct solution to this ASAP.

Has anyone considered or replaced the valve between the charcoal Canister and the intake which is supposed to vent the gas? Mine is mounted on the intake right on top. There is supposed to be a check engine light if this isn't working properly but then again we should all be getting evap DTCs as well.

 

[suprarx7nut]

Mine vents under the hood from the Canister if i don't vent it from the gas cap. And it takes forever. When this does happen i have to make a decision which is more dangerous. We really need to find the correct solution to this ASAP.

Has anyone considered or replaced the valve between the charcoal Canister and the intake which is supposed to vent the gas? Mine is mounted on the intake right on top. There is supposed to be a check engine light if this isn't working properly but then again we should all be getting evap DTCs as well. View attachment 2744708

If you have vapors venting into the engine bay, I think you have a different fault than normal. The evap system should shut itself off when excess pressure is recognized. That should then lead to the gas cap venting (unless you've modified/swapped to a sealed gas cap).

Unless the pre 06 models have a vastly different evap system....

 

[archerwolf]

Mine vents under the hood from the Canister if i don't vent it from the gas cap. And it takes forever. When this does happen i have to make a decision which is more dangerous. We really need to find the correct solution to this ASAP.

Has anyone considered or replaced the valve between the charcoal Canister and the intake which is supposed to vent the gas? Mine is mounted on the intake right on top. There is supposed to be a check engine light if this isn't working properly but then again we should all be getting evap DTCs as well.

I replaced that VSV valve on the charcoal canister under the hood (99 LC) and it is one of the things that solved the fuel venting at heat/high altitude issue for me. I also replaced all those evap lines running to the canister from the engine. That valve should hold pressure if its working correctly and excess pressure should vent from the gas cap. The VSV did not trigger any codes.

Reducing/relieving pressure lowers the boiling points of fluids. If the fuel tank is hot enough for the fuel to boil, popping the gas cap is just going to make it boil more. You'll lose a higher volume of gas and have a higher concentration of fuel vapors as well as liquid fuel coming out of that open fill tube. A good OEM gas cap will relieve enough pressure to keep the tank safe while preventing your car from being enveloped in a cloud of ignitable fuel vapor.

 

[vjpkrmnc]

So...there's....a design flaw then?

start on page one.

I hope no one thinks you should add an air to air intercooler to control fuel temp.

I have read this thread top to bottom, twice. It seems like we're circling around engine coolant. My 2006 was solid at 195.8 even for a week in Palm Springs at 110 ambient. My cooling system is fine. And I've had boil/stall twice within a few months, albeit at elevation. I feel like we're too focused here on engine cooling. I have an ARB bumper, a slee steel skid plate, slee sliders, and at the time had the (super heavy) arb base rack plus 32" tires. I'm slowly ripping it all off because I think it makes my 4.7 and xmsn work too hard in the hills. Stall/no-restart only ever happened to me on 55 mph limit hills at 7000+ elevation where the transmission had to work and the engine was up to 3500-4000 rpm just to maintain 55mph. I just am of the opinion it's not about the stock cooling system as much as it's the crap we're loading onto it--or that the combination of those two plus original design specs take us out of what the fuel system/temps were tested for. Sure older rigs by and large have stock engine cooling system degredation but that doesn't explain this happening on those like mine that do not. Which is why I'm frustrated with the 700 posts on this thread pointing back to lack of stock system maintenance. That's a contributing factor on some for sure(!), but not the primary reason why many of us are boiling fuel and experiencing "vapor lock" symptoms--in my humble opinion. Just maybe that's why few experienced these problems in the early years, because there were fewer "built", fewer with engine cooling system decay, and just fewer being used at high temps and altitude. All that leads me to ask why a fuel system cooling option wouldn't solve this for higher engine/xmsn/temp/altitude scenarios, even than as designed.

 

[jerryb]

all true, what needed to be said has already been said, and will be said again on page 50.

 

[2001LC]

Replacing 250K old bits.

View attachment 2742300View attachment 2742299View attachment 2742301View attachment 2742302View attachment 2742303

@Onur. By any chance, did you see any signs of charcoal outside of canister? Or perhaps, blow out lines and find some charcoal?

I replaced that VSV valve on the charcoal canister under the hood (99 LC) and it is one of the things that solved the fuel venting at heat/high altitude issue for me. I also replaced all those evap lines running to the canister from the engine. That valve should hold pressure if its working correctly and excess pressure should vent from the gas cap. The VSV did not trigger any codes.

Reducing/relieving pressure lowers the boiling points of fluids. If the fuel tank is hot enough for the fuel to boil, popping the gas cap is just going to make it boil more. You'll lose a higher volume of gas and have a higher concentration of fuel vapors as well as liquid fuel coming out of that open fill tube. A good OEM gas cap will relieve enough pressure to keep the tank safe while preventing your car from being enveloped in a cloud of ignitable fuel vapor.

Interesting the VSV did not through a code, and that replacing it helped so much!

Same question:
@archerwolf. By any chance, did you see any signs of charcoal outside of canister? Or perhaps, blow out lines and find some charcoal?

 

[DTC72]

Report from Silverton, CO a couple of weeks ago after following the top fixes from @J1000 => zero fuel boil after four days of slow trail driving at elevation. A 2005 LX in my group did have boil. I did have fuel boil doing the same trails last year. Nothing out of ordinary to report from monitoring using OBD2. Outside Temp in general in Silverton was a little warmer than last year. Next test is to continue to drive around on the road in super high Las Vegas heat which in the past has resulted in vapor lock. I am optimistic. Thanks J1000!

 

[OwnerCS]

Report from Silverton, CO a couple of weeks ago after following the top fixes from @J1000 => zero fuel boil after four days of slow trail driving at elevation. A 2005 LX in my group did have boil. I did have fuel boil doing the same trails last year. Nothing out of ordinary to report from monitoring using OBD2. Outside Temp in general in Silverton was a little warmer than last year. Next test is to continue to drive around on the road in super high Las Vegas heat which in the past has resulted in vapor lock. I am optimistic. Thanks J1000!

^^^ I can attest to this. Saw it in person.

 

[unclemat]

Report from Silverton, CO a couple of weeks ago after following the top fixes from @J1000 => zero fuel boil after four days of slow trail driving at elevation. A 2005 LX in my group did have boil. I did have fuel boil doing the same trails last year. Nothing out of ordinary to report from monitoring using OBD2. Outside Temp in general in Silverton was a little warmer than last year. Next test is to continue to drive around on the road in super high Las Vegas heat which in the past has resulted in vapor lock. I am optimistic. Thanks J1000!

What fixes specifically?

 

[DTC72]

What fixes specifically?

If you scroll up you can see the original recommendations from J1000 and also all the things I did in my posts.

 

[J1000]

Report from Silverton, CO a couple of weeks ago after following the top fixes from @J1000 => zero fuel boil after four days of slow trail driving at elevation. A 2005 LX in my group did have boil. I did have fuel boil doing the same trails last year. Nothing out of ordinary to report from monitoring using OBD2. Outside Temp in general in Silverton was a little warmer than last year. Next test is to continue to drive around on the road in super high Las Vegas heat which in the past has resulted in vapor lock. I am optimistic. Thanks J1000!

Glad to hear it!

 

[JohnnyMackerel]

@J1000 …how much of an impact do you think the fuel cooler alone had for this issue…obviously the other fixes are helping too but do you think maybe that and that alone could be the solution to the boiling? I only ask because don’t you have a fuel temp gauge and wondering if you isolated readings before and after the fuel cooler.

 

[J1000]

@J1000 …how much of an impact do you think the fuel cooler alone had for this issue…obviously the other fixes are helping too but do you think maybe that and that alone could be the solution to the boiling? I only ask because don’t you have a fuel temp gauge and wondering if you isolated readings before and after the fuel cooler.

The fuel cooler definitely helps. I don't think it's mandatory and it does introduce some more failure points so I would only recommend that if you are towing a lot or everything else isn't working well enough.

 

[JJ_SC]

I have an update to add. I documented the heat shielding I did earlier in this thread. I also replaced a rusted cat-back exhaust system and I replaced the charcoal canister. I also drilled some holes in my Asifr skid plate, under the cat. Probably doesn’t matter.

This summer the Cruiser has been on several trips. The biggest test was in the eastern Sierra. Multiple days at altitude between 8 - 10 thousand feet, off-road driving. Outside temps in the 90’s on average with one day up to 116 at about 9000ft. I monitored the ECT the whole time and it basically hovered around 196 - except for that one day. That day I had the AC blowing as we climbed off road for about an hour, not paying attention, just enjoying the ride. Then I looked down at the outside temp, saw it was 116, checked the ECT and it was 112. I shut off the AC and it quickly dropped to 206. Then slowly fell to 201 - 198.

So far, after the heat shields and stuff mentioned above, I haven’t had any fuel boiling issues. ECT at 112, outside temp at 116. Slow, 1st gear climb at 9000ft. No boil. Knock on wood! I hope it stays that way.

 

[2001LC]

I have an update to add. I documented the heat shielding I did earlier in this thread. I also replaced a rusted cat-back exhaust system and I replaced the charcoal canister. I also drilled some holes in my Asifr skid plate, under the cat. Probably doesn’t matter.

This summer the Cruiser has been on several trips. The biggest test was in the eastern Sierra. Multiple days at altitude between 8 - 10 thousand feet, off-road driving. Outside temps in the 90’s on average with one day up to 116 at about 9000ft. I monitored the ECT the whole time and it basically hovered around 196 - except for that one day. That day I had the AC blowing as we climbed off road for about an hour, not paying attention, just enjoying the ride. Then I looked down at the outside temp, saw it was 116, checked the ECT and it was 112. I shut off the AC and it quickly dropped to 206. Then slowly fell to 201 - 198.

So far, after the heat shields and stuff mentioned above, I haven’t had any fuel boiling issues. ECT at 112, outside temp at 116. Slow, 1st gear climb at 9000ft. No boil. Knock on wood! I hope it stays that way.

Did you also clean your radiator fins?
I assume you meant to write ECT at "212F" rather than "112"?

ECT jumping up, especially if does so fast into 200F+ w/AC on, when stopped or moving slow. Is often associated with one or all 3 radiator fins being clogged.

Take note: Dash OAT reading is not always representative of ture outside air temp. This is especially true with aftermarket front bumper.
Example: If I do a lengthy wash of front end i.e radiator and area. The iron/steel of bumper and frame gets cooled down. I've seen it take 2 hours driving in hot sun to reach true OAT. Same is true if front end in the sun on a hot day. The metal can really retain the heat for a long time.

 

[J1000]

. That day I had the AC blowing as we climbed off road for about an hour, not paying attention, just enjoying the ride. Then I looked down at the outside temp, saw it was 116, checked the ECT and it was 112. I shut off the AC and it quickly dropped to 206. Then slowly fell to 201 - 198.

On long hot climbs like that just shift down into 2nd or even 1st if you have to to get the RPMs up above 1200 or so. Once the revs get up there the cooling fan works way better. Had that happen to me a couple times just climbing slowly in 4th and temp creeps up

 

[JJ_SC]

Did you also clean your radiator fins?
I assume you meant to write ECT at "212F" rather than "112"?

ECT jumping up, especially if does so fast into 200F+ w/AC on, when stopped or moving slow. Is often associated with one or all 3 radiator fins being clogged.

Take note: Dash OAT reading is not always representative of ture outside air temp. This is especially true with aftermarket front bumper.
Example: If I do a lengthy wash of front end i.e radiator and area. The iron/steel of bumper and frame gets cooled down. I've seen it take 2 hours driving in hot sun to reach true OAT. Same is true if front end in the sun on a hot day. The metal can really retain the heat for a long time.

Sorry, yes - I meant 212. I had stopped and was at idle for at least 5 minutes before I looked at the temp.

I did do the radiator fin washout the best I could. The cooling system was flushed and pressure tested about 2 years ago (probably less than 10,000 miles. Not a daily driver anymore.) However, it was done by my trusted mechanic and I’m sure it’s not to the same level that you prescribe, Paul!

Over all the trips combined this summer, with multiple mountain passes between 4 and 8000 ft (In various parts of the Sierra) and average temp in the 80s, that was the only time it went over 200. Mostly sits at 196. 2006, maybe that’s normal for that year?

Agree about the dash temp. I think it’s a ballpark number. I still run the stock bumper but I have a winch stuffed in there behind it. I’ve check the temp reading against a friend’s jeep dash temp a bunch of times and we are usually within one or two degrees of each other. So, it’s probably not 100% accurate, but, like I said, it’s in the ballpark.

@J1000 - good idea. I’ll use that next time.

Anyway, I would love to know what the true normal operating temp is for the 2006 motor. I’m at 160,000 miles. I’m the original owner, I’ve done all the scheduled maintenance plus extra. I feel like it’s probably in spec. But, I’ll start replacing stuff if need be.

 

[2001LC]

194 to 197F seem about right w/OAT 80s plus, w/AC on. Popping to 200 or a little above now and than is normal, in 100F OAT depending on MPH.

Even taking radiator out to wash fins, is not 100% effective. We need to keep repeating as often as practical.

 

[Asanka]

On long hot climbs like that just shift down into 2nd or even 1st if you have to to get the RPMs up above 1200 or so. Once the revs get up there the cooling fan works way better. Had that happen to me a couple times just climbing slowly in 4th and temp creeps up

04 LC100, 196k, new radiator and cooling system refreshed at 180k, heavy with front and rear bumpers, winch, 15gallon water or fuel, roof rack, 270 awning, fully loaded for few days camping, but no belly armors except stock skid plates.

Never experienced vapor lock to date but few times boiling and releasing vapor. Experienced vapor/boiling issues at different elevations but not that high as Colorado mountains. Few common thing noticed at these boiling/vapor situations are,

1. Highway speeds, over 50mph.
2. Inclined/climbing roads.
3. LC struggles to keep up with the speed when climbing - slowing down gradually but not switching to lower gear, gave more gas but still slowing without switching to lower gears (more on this below).
4. Coolant temp (from torque pro) never exceeded 199, usually around 194-196.
5. Dash OAT - 80s to 90s (I don't see this is relevant unless a difference like winter vs summer)

Last week I did engineer pass, Kendal mountain and black-bear pass with 10% ethanol mix fuel. Didn't notice any boiling/vapor issues. But on the way back near Santa Fe had boiling/vapor releasing at a rest stop. No vapor lock experienced yet though. I believe this is related to No. 3 above. At those passes, I didn't give more gas than engine needed to maintain the slow climb. But on highway climbs, I gave more gas to keep up with the speed. But LC was gradually slowing down without switching to lower gears.

Nearly 33inch 285 tires messed up gearing I believe. That may be the reason not switch down to lower gear when it should. I started lowering the gear by pulsing the accelerator when it fails to keep up with the speed (I could use the Manumatic gear swifter but accelerator is fun). I wanted to test boiling/vapor issue when engine rev is high as needed for the climbs. But didn't get enough opportunities to this theory, will try again in the next road trip.

 

[Catskills]

Hey, all, reading through this thread again and having issues with my 07.

New gas cap and charcoal canister. Zero pressure at cap.

No issues at all on a daily basis.

Just bought a camper and towing it over hills brought back the gas fumes. Ethanol-free gas and it disappears.

270k miles, built truck, but towing well within my limits at 3500 lbs and a few years ago hauling my horse never had this problem.

Any ideas? Just stick with non-ethanol when I'm pushing the engine?