Thanks for that information. I have been curious about this valve. Sadly, it looks like you may have to drop the tank to get to it, but I could be wrong. I know on Alvin's truck that it blows from the the canister to the tank freely. I don't know if this is good for the fuel cutoff valve though.
Excessive fuel tank pressure
- Thread starter MaddBaggins
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This is the point exactly I've been trying to make; you cannot test this system by blowing hard into the lines ... you've gotta get the pressures preferably below 2psi or you are always going to overcome the obstructions/restrictions/faulty valves.
What type of pressure did you use to pressurize the tank such that you could hear hissing out of the charcoal canister?
The fuel cutoff valve is a good place to start searching on most vehicles, if it is at all corroded/clogged/ etc it might make a difference but again you're not gonna isolate that by blasting 15+ psi through the system!
here I am asking about topping off and how level the truck might be and forgot the simple fact that off roading usually means the fuel tank is well above the CC at times.
What keeps the fuel in those situations out of the CC?
What keeps the fuel in those situations out of the CC?
Anti-gravity
*backs away slowly*
Sorry, couldn't resist. GL everyone, this thread has been a very interesting read
Its not so much whether the tank is "higher" than the charcoal canister; its whether the tank and the tank tube is overfilled and then allowed to tip such that the fuel fills the overflow tube. If the fuel is "just" in the tank this isn't a problem. I imagine even overfilling to the top of the tube and then taking corners could slosh some fuel into the overflow tube too. The whole thing is ... don't overfill the tank.
I "think" I've solved the problem for my 80:
After narrowing the problem down to the slow venting from the tank to the canister, I suspected the fuel cut off valve at the top of the fuel tank. However, I couldn't be sure that it wasn't simply a build-up inside the "tank" line between the canister and the fuel tank.
Steps:
I actually used a shot of throttle body cleaner first, and chased it with two shots of fuel injector cleaner. I tried not to blow it continuously as I wanted some of the cleaner to stay on the valve.
Bottom line: I've filled up twice since this procedure, and I didn't have any build up of pressure when I removed the gas cap for the first time in over a year. I should probably retest the system by pressurizing the tank via the same "tank" hose and confirming that the pressure exits via the tank hose normally now (where it was exiting extremely slowly before). Also note that for this test, the exact pressure wasn't important for me - I simply had very low air flow thru the tank line.
Good luck!
After narrowing the problem down to the slow venting from the tank to the canister, I suspected the fuel cut off valve at the top of the fuel tank. However, I couldn't be sure that it wasn't simply a build-up inside the "tank" line between the canister and the fuel tank.
Steps:
- Disconnect the "tank" line at the canister
- Open gas cap
- Pour fuel injector cleaner into this "tank" hose
- Use air compressor to blow the cleaner down the "tank" hose and thru the fuel cut off valve into the fuel tank
- Repeat steps 4-5
I actually used a shot of throttle body cleaner first, and chased it with two shots of fuel injector cleaner. I tried not to blow it continuously as I wanted some of the cleaner to stay on the valve.
Bottom line: I've filled up twice since this procedure, and I didn't have any build up of pressure when I removed the gas cap for the first time in over a year. I should probably retest the system by pressurizing the tank via the same "tank" hose and confirming that the pressure exits via the tank hose normally now (where it was exiting extremely slowly before). Also note that for this test, the exact pressure wasn't important for me - I simply had very low air flow thru the tank line.
Good luck!
Those heep guys are really quite useful, they're so used to fixing things. Hehe.
But seriously, if thats the fix, good job. I may have to do it to mine even though I've never experienced any excessive venting. This sounds like something that should be done every ten years, I could only imagine what the cut-off valve looks like after that long.
But seriously, if thats the fix, good job. I may have to do it to mine even though I've never experienced any excessive venting. This sounds like something that should be done every ten years, I could only imagine what the cut-off valve looks like after that long.
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Ha! So true..
Please keep us updated on this possible fix.
Last month I did a trip filled up at around 5000ft and got to the camp spot @ 10,200 . I did not think the dang tank was gonna stop venting I had to walk away it was so bad. I hope this is the fix.
ken
Last month I did a trip filled up at around 5000ft and got to the camp spot @ 10,200 . I did not think the dang tank was gonna stop venting I had to walk away it was so bad. I hope this is the fix.
ken
Any more progress or reports on this?
My issue and symptoms I just experienced in socal this weekend. Full tank fill at 500 ft elevation (costco 87) up to 4000 ft back down to -20 ft in the desert Ocotillo wells. It was 102 and I was wheeling with 1/2 tank with venting to what appeared to be near the charcoal can. It had a very obnoxiuos bad fuel vaper smell that would burn you eyes when close to the appparent sourse. Much like in the pits of a top fuel dragster tuning a running motor. Pulled the gas cap at the end of day to add fuel and it vented for 5 -6 seconds then no more smell from under the hood. Coming home it was at about 1/4 tank pulling a trailer in 90 degree heat and no smell or venting at all. Refilled and now the tempurature is down. Seems like maybe a CC overload from the hot tempature combined with AC on and off camber wheeling.
My issue and symptoms I just experienced in socal this weekend. Full tank fill at 500 ft elevation (costco 87) up to 4000 ft back down to -20 ft in the desert Ocotillo wells. It was 102 and I was wheeling with 1/2 tank with venting to what appeared to be near the charcoal can. It had a very obnoxiuos bad fuel vaper smell that would burn you eyes when close to the appparent sourse. Much like in the pits of a top fuel dragster tuning a running motor. Pulled the gas cap at the end of day to add fuel and it vented for 5 -6 seconds then no more smell from under the hood. Coming home it was at about 1/4 tank pulling a trailer in 90 degree heat and no smell or venting at all. Refilled and now the tempurature is down. Seems like maybe a CC overload from the hot tempature combined with AC on and off camber wheeling.
Are you saying poor the cleaner down the line for overflow to the CC? So that it cleans that line without going into the CC?
MaddBaggins
Remember the KnightRider!
- Thread starter
- #112
At this point I can no longer check what s going on. It's cooled off enough the last 2 months that I don't have any issues anymore. I only had issues during the hottest months.
Until next summer, I got nothing.
Until next summer, I got nothing.
This will be of absolutely no help, but my '76 FJ55 used to have similar problems. I never did solve things, even though there was a plastic valve that I used to swap out that made me feel better about it and sometimes even actually seemed to help. In the end, I have a feeling it is just as big a mystery as you have here, sort of like those Superstition Mtns. out that way.
Yes. I isolated my problem to blockage between the tank and the CC - not the CC itself. So I'm sure my problem is either in the hose from the tank to the CC or in the valve on top of the tank going into this hose. I put cleaner into this hose and hit it with air pressure to spread it thru the hose.
NOTE: after 3 good fillups after doing this, my tank pressure came back. I haven't worried about it enough to perform this cleaning again, but I should. I can't say that other people's issues are the same as mine since the CC can certainly get clogged up. I'm just afraid that my problem is a defective valve on top of the tank, and I don't need to fix it bad enough to drop the tank.
Hope this helps -
What line is it a disconnect on the CC? I take it I poor the clean down the small hole under the gas cap? What cleaner did you use?
No. Find the charcoal canister under the hood on the USDS. The hose marked "tank" should be the outside-most hose. Remove this hose, and pour cleaner into this hose. This hose connects the fuel tank to the charcoal canister, so we're trying to clean out any build-up in the hose. You'll need to use air pressure to push the cleaner all the way back to the tank.
Hope this helps -
There are pics of the valve you guys are talking about at the end of this thread:
https://forum.ih8mud.com/80-series-tech/294253-my-next-project.html
https://forum.ih8mud.com/80-series-tech/294253-my-next-project.html
Grassy ass senor.
How hard to get to that little check valve with the tank in place? Do you think it can be replaced without dropping the tank?
I don't really worry about this much anymore, but this valve failure is the only thing I think it could be in Alvin's case and maybe mine.
Besides, it has cooled off and not a problem any more
MaddBaggins
Remember the KnightRider!
- Thread starter
- #120
Couple thoughts on this:
My timing is turned up to 7* versus the stock 3*. Could this lead to any conditions that cause my system to not be able to handle the excessive vapor during the summer?
Also, would there be any advantage/disadvantage to plugging my line from the tank to the CC directly into the manifold and just feed the vapor straight in? Bypass the CC.
Could a faulty EGR cause any issue's that could lead to the system not handling the excessive vapor?
And again, because this only happens in summer, I am beginning to be inclined to agree that the higher the ethanol in the gas, the lower the boiling point. Tucson sits at 2200'+ elevation which also lowers the boiling point. Then heading into the mountains on a HOT day lowers the boiling point even further.
My timing is turned up to 7* versus the stock 3*. Could this lead to any conditions that cause my system to not be able to handle the excessive vapor during the summer?
Also, would there be any advantage/disadvantage to plugging my line from the tank to the CC directly into the manifold and just feed the vapor straight in? Bypass the CC.
Could a faulty EGR cause any issue's that could lead to the system not handling the excessive vapor?
And again, because this only happens in summer, I am beginning to be inclined to agree that the higher the ethanol in the gas, the lower the boiling point. Tucson sits at 2200'+ elevation which also lowers the boiling point. Then heading into the mountains on a HOT day lowers the boiling point even further.
