Excessive fuel tank pressure

[alia176]

Beno's suggestion is fine if you don't have emissions, AND if you don't spend a lot of time driving up above treeline in CO

The worst venting occurs when I am wheeling up really high, and it becomes so bad that it practically gases me out of my truck. So, I'll probably throw on another aftermarket canister next year and call it good for a few more years. The AM canister is not as good as OEM...just like everything else that junky you throw on your truck!

The un-burnt vapor can be nasty for your trail spotter too which I found out when I ran w/o the cats for a short while. All that sloshing really stirs up the fumes.

 

[JaketheSSnake]

Just had this happen to me a few days a go. Really bad fuel smell to the point that my wife was ready to bail with the kids. Cracked the fuel cap and it hissed like crazy. Drove a little bit further (maybe 15 miles) and the smell was back. Cracked the fuel cap again and it hissed, but not as bad. I put a new vc120 in about 10k miles a go and it's been fine until now. Ive only put ethanol in it when there was no other option, and probably haven't had to for a good year or so. The tank was around 5/8 to half full. I filled it and it went away. I hope it was just a fluke because if I have to fill it before it gets to the half tank, I'll never be able to go anywhere lol

 

[Runtble]

Hate to bump an old thread, but I swapped my CC to the VC120 and this weekend after a quick drive up about 4000 feet over an hour in 90 degree weather caused a very very high amount of tank pressure. Did I do something wrong?

 

[BILT4ME]

Hate to bump an old thread, but I swapped my CC to the VC120 and this weekend after a quick drive up about 4000 feet over an hour in 90 degree weather caused a very very high amount of tank pressure. Did I do something wrong?

Did you get the hoses attached in the correct order?

Were you running ethanol fuel?

When you go to elevation with ethanol fuel, it boils off hard.

Still should not have pressurized that much.

 

[Runtble]

Did you get the hoses attached in the correct order?

Were you running ethanol fuel?

When you go to elevation with ethanol fuel, it boils off hard.

Still should not have pressurized that much.

Yes, tank and purge are appropriately connected.

I believe Costco uses E10 (10% ethanol).

I disconnected both hoses to verify that there was vacuum on the intake manifold (purge) side, and when disconnecting the tank side, it was releasing vapor.

It is worth noting that I did find that my fan shroud was not making a good seal, and that this may have been causing excess heat, possibly boiling the fuel on the return line.

 

[surfpig]

Hate to bump an old thread, but I swapped my CC to the VC120 and this weekend after a quick drive up about 4000 feet over an hour in 90 degree weather caused a very very high amount of tank pressure. Did I do something wrong?

Maybe. EDIT: posted just before me, maybe you hooked it up wrong? I'm going on 5 years with no issues at all, up to like 10000 feet elevation...

 

[greentruck]

Yeah, if that canister was loaded with fumes and the heat went way up, that could make a marginal situation nasty.

The shroud is pretty darn necessary to get proper cooling IME. Farted around with mine and got it AL duct-taped good 'nough since R&Ring the radiator a few years back. Finally have a new shroud on hand, just waiting on getting a new fanblade to do both at the same time.

Also looking forward to trying this fix on our truck. Gotta get the AC fixed first, first thing in the morning.

 

[Summiteer]

Do you have a way to check your engine temps? I was having the same issue at high altitudes, swapped canisters, it was hooked up right but still had a lot of venting. Fan clutch ended up being the culprit. Rebuilt it with 30k silicon oil and all the venting from the gas cap went away.

 

[Runtble]

After replacing the fan shroud, I've had absolutely no venting issues. Thanks for the people who helped out with suggestions!

 

[Flovalflyer]

Bumping up an old post from the dead. Since it's getting to summer again is there any new information from anyone experiencing the boiling gas issue? I ran WABDR a few weeks ago and experienced the boiling issues under the normal set of circumstances: hot temps, elevation gains, ethanol gas, heavy load, slow speeds. Working on replacing the CC and updating the basics in the cooling and fuel systems now in prep for a trip to CO in a couple of weeks. I know others have this issue and I feel there's a silver bullet out there that has yet to be found!

 

[LandCruiserPhil]

Bumping up an old post from the dead. Since it's getting to summer again is there any new information from anyone experiencing the boiling gas issue? I ran WABDR a few weeks ago and experienced the boiling issues under the normal set of circumstances: hot temps, elevation gains, ethanol gas, heavy load, slow speeds. Working on replacing the CC and updating the basics in the cooling and fuel systems now in prep for a trip to CO in a couple of weeks. I know others have this issue and I feel there's a silver bullet out there that has yet to be found!

I put an end to my Charcoal Canister problems for good!

In the past I rebuilt my canister but recently the problem popped back up and once I experience a problem 3 times I change directions and look for a final fix. The canister has 3 lines - 1 - comes straight from the tank with a one way valve at the canister < the problem 1 - goes to the VCV...

forum.ih8mud.com

 

[Flovalflyer]

I put an end to my Charcoal Canister problems for good!

In the past I rebuilt my canister but recently the problem popped back up and once I experience a problem 3 times I change directions and look for a final fix. The canister has 3 lines - 1 - comes straight from the tank with a one way valve at the canister < the problem 1 - goes to the VCV...

forum.ih8mud.com

Thanks LCP. I've got a VC120 ordered and looking at drilling out my existing CC. Has anyone had experience with drilling the CC eliminating the boiling gas issue? I understand how it would reduce tank pressure but my thinking is that there is heat being added to the system which is causing the boiling in the tank that may not be eliminated by pressure reduction and may exaggerate it due to the physics of how pressure and boiling points are dependent and directly related.

 

[LandCruiserPhil]

Thanks LCP. I've got a VC120 ordered and looking at drilling out my existing CC. Has anyone had experience with drilling the CC eliminating the boiling gas issue? I understand how it would reduce tank pressure but my thinking is that there is heat being added to the system which is causing the boiling in the tank that may not be eliminated by pressure reduction and may exaggerate it due to the physics of how pressure and boiling points are dependent and directly related.

I live in Arizona and I have no boiling or any fuel pressure issues since fixing the problem.

 

[wer1952]

Thanks LCP. I've got a VC120 ordered and looking at drilling out my existing CC. Has anyone had experience with drilling the CC eliminating the boiling gas issue? I understand how it would reduce tank pressure but my thinking is that there is heat being added to the system which is causing the boiling in the tank that may not be eliminated by pressure reduction and may exaggerate it due to the physics of how pressure and boiling points are dependent and directly related.

 

[wer1952]

I am glad I found this thread, because I have had this problem for years with a 1995 FJ80.

Let me say up front that I 100% agree that the gasoline is boiling. Not to belabor a point, but I am a chemist and I have done more distillations than I can remember. The gasoline is boiling, I can guarantee you that. On my last trip up Silver Canyon Road in the California White Mountains it lasted 40 minutes (!) at about 11,000 ft on a nearly full tank of gas. I am not exaggerating, this was by far the longest I have experienced this. I shut off the engine, pulled out a camp chair and waited for it to stop while gasoline fumes billowed out of the gas tank. So, venting, replacing charcoal canisters etc. is not going to fix the basic problem, which is overheating of the gasoline.

For gasoline to boil for that long, there has to be a heat source, and the heat source persists with the engine shut off. First, I thought this was something uniquely wrong with my vehicle, and the only thing I could come up with is that I have an aftermarket catalytic converter, which I know runs pretty hot. It is far away from the gas tank, though. Has anyone else installed an aftermarket catalyst?

Since multiple people have this problem, it may be a design issue. It looks like a significant heat sink builds up over time that keeps radiating enough heat to keep the gasoline boiling. The exhaust system runs pretty close to the gas tank, but that the exhaust system alone would not likely be enough of a heat sink to cause all this. It looks like the entire undercarriage of the vehicle slowly heats up.
The problem does not appear to be an overheating engine. According to my temperature gauge, my engine temperature is just fine.

This only happens when driving slowly uphill on a hot day, with not a lot of air flow because of the low driving speed. This may sound crazy, but I am seriously thinking about installing a cooling fan in front of the gas tank. There is plenty of space up high enough that it would be well protected. Thoughts, anyone?

 

[rcracin]

Hmm what about an air scoop of some sort to direct air underneath. An inlet at the front and outlet to the rear.

Or maybe the fuel tank cover is trapping heat? What about drilling holes in the cover?

 

[wer1952]

Hmm what about an air scoop of some sort to direct air underneath. An inlet at the front and outlet to the rear.

Or maybe the fuel tank cover is trapping heat? What about drilling holes in the cover?

That's not a bad idea, especially the scoop..... Not sure it is enough, but it will probably help.

 

[FirstToy]

It's the RVP of the fuel, not the ambient temp, correct?
If the fuel will vaporize at 120f, not much you can do to cool it off.

From what I understand,
We can't get no ethanol fuel anymore, so if you get a station mixing a lot in, it will boil sooner.

I think we get high 'stress' situations where we will be driving at 100+F, sea level, then rapidly move up to 5000-10k'
with a hot tank of fuel. Managing vaporizing 20gallons of gas is a challenge.

I've seen it happen on other rigs, not just 80s. I don't know the answer, except it is probably a combination of factors

Only answer I've had is to keep the system in as good condition as possible.

 

[Pskhaat]

I am glad I found this thread, because I have had this problem for years with a 1995 FJ80.
?

Happened just like this ALL THE TIME in my old 96 fzJ80. As I recall the cats were not a world market addition for the 1FZ(FE) and as a emissions add-on created significant heat sources whilst the original design did not take those into account. The ECU (unlike in the same afterthought 3fe) was remapped with post-cat sensors.

As only 'muricans would ever clamor for a V8 gasser, I assume the cats were original design of the uzj100, but maybe the fuel system and routing are consistent across the lc100.

It's a design problem starting with the 1FZ. Does the UR engines do this?

 

[Dimples]

Happened just like this ALL THE TIME in my old 96 fzJ80. As I recall the cats were not a world market addition for the 1FZ(FE) and as a emissions add-on created significant heat sources whilst the original design did not take those into account. The ECU (unlike in the same afterthought 3fe) was remapped with post-cat sensors.

As only 'muricans would ever clamor for a V8 gasser, I assume the cats were original design of the uzj100, but maybe the fuel system and routing are consistent across the lc100.

It's a design problem starting with the 1FZ. Does the UR engines do this?

Happened in my 3fe all the time as well until I rerouted the exhaust away from the fuel tank and fuel lines. Post exhaust reroute I have 0 boiling/excess fume pressure at any elevation.

Another option could be additional heat shielding.