Excessive fuel tank pressure (1 Viewer)

[MaddBaggins]

I've been chasing a fuel tank pressure issue for some time now.
Last year I noticed when I drove up nearly 6k feet in less than 1 hour in July I had a bad gas smell and a whining from the drivers front. I opened the gas cap and it vented for (I kid you not) 10 minutes.
Some time after that it happened again and I began chasing the problem in the FSM. I ran the FSM test on the charcoal canister and the 2 check valves under the throttle body. The charcoal canister failed and the check valves passed. I replaced the canister, not cheap.
I haven't done any hot trips with big elevation change until this last weekend. The problem is still there. I had big time pressure and when we stopped for lunch, I smelled gas and heard a whine again. I opened the gas cap and it vented for a few minutes then began to spew gas. I promptly closed it again and we finished the trip.

Obviously, the fuel vapor from the tank is not making it to the throttle body and being recycled like it should. The line from the canister to the tank is clear BTW, the canister is new and the 2 check valves passed the FSM test.

Any ideas?

 

[MaddBaggins]

BTW, the exact thing thing is happening to a.mus.ed 95 80 as well. So if we figure out whats wrong with mine we can fix his as well.

 

[nat88toy]

happened to a friend of mine he was wheeling in 90* temps in low range with his AC on doing 5mph, when we stopped we notice he was over heating and his charcoal canister was making an electrical arcing type noise so he removed his gas cap and vented for a good 10 minutes he managed to boil off 5 gallons of gas
This only did this to him once we think it was caused by the engine slightly over heating and heating the fuel going threw the return line. We washed out all the dirt from the radiator and fixed his fan clutch that wasn't working haven't had the problem since
btw he had a 92 with a 3f
funny thing was it sounded like some one pulled the shrader vales out of there tire when it was venting yup he was driving a bomb

 

[landtank]

there is a line on the bottom of the charcoal canister that runs down to a nipple mounted to the frame. Check to make sure that the other end of that nipple is clear and open.

 

[MaddBaggins]

there is a line on the bottom of the charcoal canister that runs down to a nipple mounted to the frame. Check to make sure that the other end of that nipple is clear and open.

That line is clear. I opened the gas tank and blew air thru that line and witnessed vapor come out of the tank.

 

[Clutchee]

Look in the FSM & there is a cleaning procedure & then a check procedure for the Charcoal Canister....... same thing happened to a buddies 80 when wheeling.

We did the test procedure & it was bad.

Hope this helps.

 

[MaddBaggins]

happened to a friend of mine he was wheeling in 90* temps in low range with his AC on doing 5mph, when we stopped we notice he was over heating and his charcoal canister was making an electrical arcing type noise so he removed his gas cap and vented for a good 10 minutes he managed to boil off 5 gallons of gas
This only did this to him once we think it was caused by the engine slightly over heating and heating the fuel going threw the return line. We washed out all the dirt from the radiator and fixed his fan clutch that wasn't working haven't had the problem since
btw he had a 92 with a 3f
funny thing was it sounded like some one pulled the shrader vales out of there tire when it was venting yup he was driving a bomb

No overheating or low range only driving involved. It only happens when it's hot and I do big elevation changes, IE more than a couple thousand feet.

I drove the same 6k elevation gain in may during a cold rainstorm and had no issue. I believe it is a combo of heat and elevation.

 

[landtank]

That line is clear. I opened the gas tank and blew air thru that line and witnessed vapor come out of the tank.

I meant pull the nipple assembly out of the frame. One of our members lost three tanks because it was clogged.

 

[MaddBaggins]

Look in the FSM & there is a cleaning procedure & then a check procedure for the Charcoal Canister....... same thing happened to a buddies 80 when wheeling.

We did the test procedure & it was bad.

Hope this helps.

Did all that, as mentioned in my post. My canister failed and I replaced it. That did not fix the issue.

 

[MaddBaggins]

I meant pull the nipple assembly out of the frame. One of our members lost three tanks because it was clogged.

I'll check that again, but I blew thru that entire line from the bottom of the canister back to the tank.

 

[nat88toy]

hows your fan clutch?

 

[MaddBaggins]

hows your fan clutch?

Oh my cooling system is better than most here. I'm running 15k cst fluid in the new blue clutch, and in 07 I replaced the radiator, hoses and t-stat as well as a full system flush and new Toy Red and Water Wetter.

Where you going with that?

 

[nat88toy]

Oh my cooling system is better than most here. I'm running 15k cst fluid in the new blue clutch, and in 07 I replaced the radiator, hoses and t-stat as well as a full system flush and new Toy Red and Water Wetter.

Where you going with that?

ok that rules out the whole overheating of fuel from a crappy cooling system, my buds cooling system was well junk and causing his fuel to over heat when his ac was on, just trying to systematically rule thing out

hopefully he chimes in he may have some more insight into the problem ill give him a call tomorow and see if there was anything else he did to fix the problem i dont know of

 

[turbocruiser]

Have you checked the returns too? BTW, you should not use Redline WW with Toyota Red, causes a sludge throughout the system and has caused some cooling issues for a few folks. HTH.

 

[AdventureBuddies]

Man. Every time I think I have e every little issue in the truck taken care of, I see a post like this and I think "Hey,that's happened to me before but I didn't know anything could be done about it."

it happened to me after gaining about 5000 ft after just filling the tank and sub tank. Gas started seeping past the fill cap and I had to vent it for a long time to relieve the pressure. So it sounds like I have some trouble shooting ahead of me. Or could it have been an isolated event?

 

[a.mus.ed]

like alvin said, i've had this twice on my 95. both times were after climbing several thousand feet in high temperatures. both times i opened my tank to allow it to vent. both times the tank vented heavily for 10-15 minutes. i haven't done any diagnostics yet as both times just happened in the last 2 weeks.

 

[gotmud]

I've got the same issue as well. Only thing is, I don't need to gain elevation for my tank to build up pressure. Any warm day with a tank less than full, and I can expect it to vent when I remove the cap. Never for ten minutes though. I have replaced the canister too. I also checked the lines from the canister to the tank. The check valves on mine are working also. I have not tried Rick's suggestion of pulling the nipple out of the frame.

 

[GeoRoss]

I had the same thing happen last summer from Tucson to Flagsaff (2200ft to 7000ft) and again from Kayenta AZ to Dolores CO. It didn't happen again that trip going to Durango CO and back home. No other problems since. I had fueled up a few weeks earlier were the pump didn't shut off. There was some over flow and I suspected I had saturated the charcoal canister. I hope I haven't naively assumed it is functioning normally as I am headed up to the high country of CO in a few weeks.

 

[IdahoDoug]

Ross, your avatar is now my favorite. Who new that bumbles bounce, and that it would still be a character in the public's awareness 50 years later??

DougM

 

[nat88toy]

if your venting for more then a couple of minutes it probably not pressure but your gas boiling that what happened to my friend

gasoline has a boiling point from 100-400* depending on additives that are use in the fuel and when your going higher in altitude that boiling point changes making the fuels boil at a lower temp may have something to do with what i see happening since most people with the problem are at a higher altitude when this happens come to think of it my friend who usually lives at see level was up around 5000ft absl when he boiled off 5 gallons

hope we can find a solution to your problem its not fun driving around a bomb