Excessive fuel tank pressure

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I am going to do a test today and see if mine is even working at all. If it opens at 3k then I am going to use the vacuum pump to see at what pressure and see if I can find another vacuum switch that opens sooner.

Talked to a toyota tech at my local dealer at lunch and he said 3K on our engines was way too high as well. Another tech suggested putting a low psi (like 1 or 2) check valve in line between the CC canister and the VCV that will vent into the standard air intake not hooked directly to the manifold. His suggestion was that way we still "trick" the engine into not thinking it has a vacuum leak and any build up of pressure will vent in through the engine.

There has to be a way to correct this.
 
Just got back from Moab...wheeled kokopelli trail and was at high altitude several times on the way to Moab from Denver. Just before leaving, I changed out the CC with the aftermarket one suggested in the other post and I had absolutely ZERO venting the entire trip. For $40, not a bad solution for those worried about the pressure build.
 
I cleaned my VCV and it seems to be working now. I also switched some of the Vacuum lines around on it. I was not suffering from excessive tank pressure but the CC venting fumes all the time so I am trying to eliminate that. As I have it now the VCV opens when the truck is running at idle and starts venting the CC. I drove it some yesterday and today and so far absolutely no fuel smell. I checked the gas cap after driving about 15 miles on the highway and no pressure (was concerned that constant suction may cause an issue). The only issue I have is that at hot idle the rpm is dropping to abt 600 which of course causes it to idle a little rough (the venting is causing a vacuum leak at such a low rpm). I think I have a fix for that I am going to try this afternoon. If my idea works then the VCV will open at about 1000 rpm and start venting. If all goes well this may be a fix for the excessive pressure as well as CC venting on the trail. I will post pictures and part numbers as soon as I get it right.
 
I just ran the McGrew Trail here in Oregon and had the boiling fuel issue again for the 3rd straight summer. Only happens on this trail in the summer. Will switch to the "cheap" canister and will be running the trail next month. Will post up my results.
 
Despite a new OEM cannister I am getting nice strong fuel smell this summer. Was 100 today in a trip to Denver and upon arriving home back in a cool 86 degrees I opened the hood and could hear a light buzzing from the cannister.

I am not getting any fuel boiling - engine temps never went above 200 according to the Scanguage II.

I'm going to replace all three lines related to the cannister to rule out any leaks. Are people still reporting the GM part as solving the problem now that the heat is on?
 
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Nay said:
Despite a new OEM cannister I am getting nice strong fuel smell this summer. Was 100 today in a trip to Denver and upon arriving home back in a cool 86 degrees I opened the hood and could hear a light buzzing from the cannister.

I am not getting any fuel boiling - engine temps never went above 200 according to the Scanguage II.

I'll going to replace all three lines related to the cannister to rule out any leaks. Are people still reporting the GM part as solving the problem now that the heat is on?
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NO my VC 120 will give me smell on sloshy slow trips in this heat just the same as a trip into town on the highway... :frown:
 
sl33p3 said:
NO my VC 120 will give me smell on sloshy slow trips in this heat just the same as a trip into town on the highway... :frown:
Click to expand...

Strange.. I changed mine out bout a year ago with the VC 120, I've got at least 15k miles on the new canister.. last year it was really bad I had to vent my gas :rolleyes: for 5 minutes at the pump on hot summer days.. Now no venting, boiling or anything, and I am in Phoenix where it's been 100+ for the last month and a half :hhmm: + it's my daily driver. :popcorn:
Maybe you got bad gas :pig: :idea: in your area? + Ethanol or something>??
 
Manuelsv said:
Strange.. I changed mine out bout a year ago with the VC 120, I've got at least 15k miles on the new canister.. last year it was really bad I had to vent my gas :rolleyes: for 5 minutes at the pump on hot summer days.. Now no venting, boiling or anything, and I am in Phoenix where it's been 100+ for the last month and a half :hhmm: + it's my daily driver. :popcorn:
Maybe you got bad gas :pig: :idea: in your area? + Ethanol or something>??
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certainly could be. i do typ use the same station so it would be the variation they typically get...:meh:

i took the vc120 to deathvalley this spring and had no issues ever (-200' to 6k'+ changes in one day). didn't have problems till it got hot here and i was out slow crawl sloshing on a trail (and i started with half a tank) since then there is always been fuel smell in the garage when i get home. not as bad as ont he trail when i could smell it in the cab, but present most days nevertheless.

i think fuel mix quality is a huge factor in the systems. my oem canister never gave me smell, but my tank would need to vent for a long time (minutes) on sloshy trips... shrug. teh vc has fixed that (clearly by venting fumes into the engine compartment) i might go back to oem. if i could buy a new oem can for a 93 i might consider that and live with "new" oem performance and not think about it anymore, but they are discontinued to my knowledge. :beer::popcorn:
 
remac226 said:
I cleaned my VCV and it seems to be working now. I also switched some of the Vacuum lines around on it. I was not suffering from excessive tank pressure but the CC venting fumes all the time so I am trying to eliminate that. As I have it now the VCV opens when the truck is running at idle and starts venting the CC. I drove it some yesterday and today and so far absolutely no fuel smell. I checked the gas cap after driving about 15 miles on the highway and no pressure (was concerned that constant suction may cause an issue). The only issue I have is that at hot idle the rpm is dropping to abt 600 which of course causes it to idle a little rough (the venting is causing a vacuum leak at such a low rpm). I think I have a fix for that I am going to try this afternoon. If my idea works then the VCV will open at about 1000 rpm and start venting. If all goes well this may be a fix for the excessive pressure as well as CC venting on the trail. I will post pictures and part numbers as soon as I get it right.
Click to expand...

Any update to this?
 
Last year, I switched my CC out with the $300+ OEM Unobtainium unit. This summer I am getting smells still (although not as bad) and I just don't fill that tank when it is super hot in the middle of the day, so can't speak to boiling off fuel. My recommendation is that the cheaper unit will perform as well as the OEM. I also agree it is most likely fuel and ethanol mixture causing it.
 
Drove around Denver/ Faiplay all weekend. Five people, two dogs and luggage and ac going the whole time. Temp gaugr was getting close to red (modded gauge) but no more fuel issues. Filled up during the midday and no more long hiss.

Autozone cannister worked for me.
 
***UPDATE***

McGrew Trail Ride was this weekend. The last 4 trail rides over the last 2 years has caused the fuel boiling issue. Ran it in June this year and boiled the fuel. Changed to the VC120 a few weeks back. Did not change anything else: fuel type or where purchased, gas cap, hoses, etc. Only changed the canister so I could troubleshoot step by step.

No fuel boiling issues. Popped the cap and got a 1-2 second whoosh and that was it. Did not smell the "old gas" or "turpentine" smell near the fuel door either. I did smell it near another 80 on the trail though.

So far so good.

(Cross posted this in the charcoal canister thread as well)
 
Thanks guies, mine is all good. I only changed the can. It has been driving me crazy trying to get it fixed. Did a serch here about a month ago and got a fix. You got to love this forum, comes through most of the time.

Phil
 
I ran an experiement this week on my way through the Colorado mountains.

In the past, I've had problems with fuel boiling at high elevation. This week, while passing through Gunninson, CO, I saw a gas station the sold Ethanol free premium fuel. Being almost empty, I filled up and drove on to Ouray, CO. The next day we drove the vehicle to the top of Blackbear Pass which tops out at 12,800 feet. When I opened the fuel tank cap, the tank was under a slight vacuum, like it should be.

Later in the week, I had to add some ethanol laden fuel and began to have slight fuel pressurization issues and would get the fuel smell while driving slow over the mountain passes.

On my way home, I again filled up in Gunnison and drove to the top of Monarch pass at 11,300 feet. I was pulling my camp trailer so it was a 1st gear, 3600 rpm, nearly full throttle pull and again the tank was under a slight vacuum at the top.

So, my hypothesis remains that the ethanol laden fuel is boiling much earlier than a non-ethanol fuel and significantly contributing to the pressurization of the fuel tank.

Adam R.
 
Did you happen to track fuel economy? I bet it went up, too.
 
No I didn't. Because I was pulling the trailer, and going over different routes, there was no opportunity to compare two different tanks of fuel.

From my house to Gunnison, CO. I got 10.1 mpg, pulling our 21 foot travel trailer using 10% ethanol laden fuel. Certainly nothing to write home about.


Adam R.
 
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