Altitude Sickness ?

[Bob22222]

Going over things without starting the truck it appears all vacuum and vapor lines associated with the evap system are correctly routed. The line to the tank is clear. At least without the pump/engine running. I cannot blow a moderate stream of air down steam past the DVD valve ( I believe it's called) cold. I can however blow air freely backward into the canister from the exit port which feeds the DVD valve.
Two pieces of information I'm seeking before I idling it to a warmup in order to further check the valve. Providing I get the canister thing (#1 below) figured out first, that is.
1. Do the canisters on these (3.0 1993 non-Cali) systems indeed incorporate a check valve to prevent back flow from the manifold vapors? Or is that left up to the DVD valve?
2. Is it vacuum/atmospheric pressure alone the control or direct the operation of the DVD valve (my, I sure hope a have the acronym for tat valve correct) or is it controlled by a bi-metal temp switch? By the way it looks like no fun to R$R with the intake manifold in place. But, I think it can be done without taking a Sawzall or sledge to the firewall.
I'm sure the answers won't be hard to find. But, if anyone knows from
experience that they do in fact know please let me and the rest of us know.

Speaking of knowing how. I need to figure out how I can add an edit/caution in contrasting caution orange to my first post in this thread pointing out that this is a rather explosive (flammable topic to say the least). And that one should not take away bits and pieces and think there is any solution resolved. There is obvious conflicting information in this thread. It a good idea to do solid research, be sure of what one's doing when dealing with this stuff and don't go over one's head. I.e. Don't try this at home and read all post throughly, ect....

 

[flyinhawaiian01]

Yep, you've got it all figured out alright!

Stant, the company that makes fuel caps is also wrong, I think you should sue them for passing on wrong information.

Stant

I'm gonna call them right now and tell them they are full of shit like you say I am and gonna make sure they re-write their faq so that it falls inline with what you've posted!

What you fail to understand, is the fact that a vented gas cap should not circumvent the charcoal canister, it should however, release the extra pressure when its too high (boy do I sound like a broken record), such as what you've experienced. If it doesn't build extreme amounts of pressure while normally driving around with little to no altitude changes, then your truck is working correctly. If it only happens when you head up in altitude, then your cap is not venting properly and you're relying on the closed system to vent only through the canister.

But whatever, you do whatever you want. Spend the 60 bucks on new parts, hopefully it fixes it and we don't have to ever hear about it again. As for me, I've tried to help but you seem to be an ass about it and I'm done with you.

Good day...

 

[Bob22222]

Yep, you've got it all figured out alright!

Stant, the company that makes fuel caps is also wrong, I think you should sue them for passing on wrong information.

Stant

I'm gonna call them right now and tell them they are full of shit like you say I am and gonna make sure they re-write their faq so that it falls inline with what you've posted!

What you fail to understand, is the fact that a vented gas cap should not circumvent the charcoal canister, it should however, release the extra pressure when its too high (boy do I sound like a broken record), such as what you've experienced. If it doesn't build extreme amounts of pressure while normally driving around with little to no altitude changes, then your truck is working correctly. If it only happens when you head up in altitude, then your cap is not venting properly and you're relying on the closed system to vent only through the canister.

But whatever, you do whatever you want. Spend the 60 bucks on new parts, hopefully it fixes it and we don't have to ever hear about it again. As for me, I've tried to help but you seem to be an ass about it and I'm done with you.

Good day...

If you can't be correct be vulgar?
Do you bother to read the links you post?
Do you know what and/or means?
Or is that to deep for your basic thought processes?
If your so sure of yourself go take the gas cap off your 94 or 95 (or what ever)pop it open take a photo of "this relief" valve and post them. After all, it's only nine bucks ( mine was 10) and I was readily willing to lay that out on your ill while maybe we'll-intended advice. That's if you think my photos are phony. Get the point: the new cap is identical to the old cap neither has a positive tank pressure vent. The same pressure buildup occurred with the new cap as did with the old cap. And by all means thank you! I'm really quite thrilled you'll be keeping the benefit of foggy your advice from me. I prefer those that speak from experience rather than the garbel they gather and don't understand.

 

[Bob22222]

If everyone's not been frightened off by the tone here I'm still trying to figure this out. Its somewhat cooler today here. Here is what I got:

1 All lines are clear

2 Intake pulls fine (rock steady and well over 20 inch/ lbs at mild throttle position). That is upstream of the valve on the suction line leading to ( or more properly whic is fed by) the purge port.

3 When fully warmed at idle (I haven't driven it to full hot yet, as promised ) there is no vapor being emitted from the line leading from the purge port. However, the slightest suction by mouth yields plenty of vapor. Pumping the hell out of it with a hand mighty vac yields no visible residue of fuel.

4 I'm leaning toward I maxed out the system unless:

mega pressure build up in gas tank - YotaTech Forums
Can some help identify the two lines mentioned in this yotatech thread? Maybe I should join over there?

 

[Bad_Vision]

I too would suspect the fuel canister and/or some associated valving. The evap canister's sole purpose in life is to trap tank vapors in the charcoal when the tank has to vent excess pressure. Then under conditions of low tank pressure it purges the vapors back out of the canister and into the intake manifold.

You could also ask the question here 86-95 Trucks & 4Runners - YotaTech Forums. Yotatech is a more active forum for 2nd gen 4runners and trucks of this vintage.

Yotatech is bad about giving you the run around.


Sent from my iPhone using Tapatalk

 

[Bad_Vision]

Really?





Quoted directly from Autozone:



The fuel cap contains an integral pressure and vacuum relief valve. The vacuum valve acts to allow air into the fuel tank to replace the fuel as it is used, while preventing vapors from escaping the tank through the atmosphere. The vacuum relief valve opens after a vacuum of -0.5 psi (3.45 kPa). The pressure valve acts as a backup pressure relief valve in the event the normal venting system is overcome by excessive generation of internal pressure or restriction of the normal venting system. The pressure relief range is 1.6-2.1 psi (11.0-14.5 kPa). Fill cap damage or contamination that stops the pressure vacuum valve from working may result in deformation of the fuel tank.



Altitude created much more pressure than the closed system could purge off, hence the reason why after opening the tank cap, pressure continued for a much longer time than normal.



With a pressure relief at ~2psi, either the OP exaggerated the amount of pressure in his system, or the cap did NOT relieve the excessive amount of pressure.



I don't throw around mis-information, and if I'm wrong or unsure about something, I will admit to it. This is not one of those times. Again, 9 dollar part to check if that's the problem, or 60 dollar charcoal canister to see if that works, which should you pick first?



I don't really care either way, you do what you like with your money, its none of my business. I'm on this forum to try to help folks with their 4runners, not get into wars about gas caps.

Yeah your gas cap is not supposed to have a relief valve in it. That's the hole reason the vapors are plumbed all the way to the charcoal canister or collection.


Sent from my iPhone using Tapatalk

 

[renosauce]

If everyone's not been frightened off by the tone here I'm still trying to figure this out. Its somewhat cooler today here. Here is what I got:

1 All lines are clear

2 Intake pulls fine (rock steady and well over 20 inch/ lbs at mild throttle position). That is upstream of the valve on the suction line leading to ( or more properly whic is fed by) the purge port.

3 When fully warmed at idle (I haven't driven it to full hot yet, as promised ) there is no vapor being emitted from the line leading from the purge port. However, the slightest suction by mouth yields plenty of vapor. Pumping the hell out of it with a hand mighty vac yields no visible residue of fuel.

4 I'm leaning toward I maxed out the system unless:

mega pressure build up in gas tank - YotaTech Forums
Can some help identify the two lines mentioned in this yotatech thread? Maybe I should join over there?

OP have you replaced the gas cap and ran down the hill again and then back up the hill and tested it?

I am curious.. about a couple things. You may be just shooting your self in the foot and not actually have any issues.
Did you plan your trip around your gas station stops?
Normally, on an empty tank filling it all the way up, you will get a lot more aeration in the gas. And since we can all agree on the fact that EFI systems are fully closed systems, that the gas cap has a vent, that vent is so the tanks don't suck them selves shut...

The idea is it lets in atmospheric pressure...so you go from 9000ft, all the way down to 5000ft that pressure inside the tank is is going to now be the atmospheric pressure of 5000ft, and if your system is working properly, had you let the gas cap off at 5000 ft, you should not of had much if any built up pressure. but now since that thing only goes one way, its a hot day, you have more air in the tank then when you started, you start heading back up the hill, hot day, that air starts to expand...you got a massive amount of pressure, and thinking you wanted to save a buck or two, your truck is now massively pressurized, Technically speaking your system should be taking some of that air and sending it back to the intake.. I have seen two lines of thoughts when this happens, both after you shut the vehicle down, or during...i believe if you are obd1 its after, and obd2 is during...i make no promises on that... but after you shut down your truck, the evap system is supposed to take that pressure and send it through the carbon canister....and so forth...

Now if i were you...id try it again.... change up a couple of the factors, time of day, dont get gas before you head down the hill. release the gas cap when you get down the hill...
.let it sit over night...and then see what happens..

If you do any of this and still have an issue when you return home.. I would try the canister as a fix, as well as the purge valve/solenoid...
but i think you may just have a normal acting system and have actually hit perfect, weirdo situation of events and not let the system catch up to it self.... but what do i know..
Maybe some one can chime in on when the EVAP system of those model Toyota, actually purge the system..

 

[Bob22222]

OP have you replaced the gas cap and ran down the hill again and then back up the hill and tested it?

I am curious.. about a couple things. You may be just shooting your self in the foot and not actually have any issues. The
Did you plan your trip around your gas station stops?
Normally, on an empty tank filling it all the way up, you will get a lot more aeration in the gas. And since we can all agree on the fact that EFI systems are fully closed systems, that the gas cap has a vent, that vent is so the tanks don't suck them selves shut...

The idea is it lets in atmospheric pressure...so you go from 9000ft, all the way down to 5000ft that pressure inside the tank is is going to now be the atmospheric pressure of 5000ft, and if your system is working properly, had you let the gas cap off at 5000 ft, you should not of had much if any built up pressure. but now since that thing only goes one way, its a hot day, you have more air in the tank then when you started, you start heading back up the hill, hot day, that air starts to expand...you got a massive amount of pressure, and thinking you wanted to save a buck or two, your truck is now massively pressurized, Technically speaking your system should be taking some of that air and sending it back to the intake.. I have seen two lines of thoughts when this happens, both after you shut the vehicle down, or during...i believe if you are obd1 its after, and obd2 is during...i make no promises on that... but after you shut down your truck, the evap system is supposed to take that pressure and send it through the carbon canister....and so forth...

Now if i were you...id try it again.... change up a couple of the factors, time of day, dont get gas before you head down the hill. release the gas cap when you get down the hill...
.let it sit over night...and then see what happens..

If you do any of this and still have an issue when you return home.. I would try the canister as a fix, as well as the purge valve/solenoid...
but i think you may just have a normal acting system and have actually hit perfect, weirdo situation of events and not let the system catch up to it self.... but what do i know..
Maybe some one can chime in on when the EVAP system of those model Toyota, actually purge the system..

Good thinking, I'm tending to the conclusion that I maxed out the system. Although, I'd like to clear up a couple of points. I start at about 8700 feet where I live. Always with a fullish tank because when you live where I live you get gas on the way home.
With about a gallon missing from the tank that's been sitting for day I head first up over the hill at about 9100 feet. Then down into traffic into the city at about 6000 feet. Parked for about an hour and a half in the hot sun (remember I started cool at altitude) so dispite the altuide drop things should already be expanding. Run errand in moderately heavy traffic very hot. Head up the hill in traffic so a lot of third and forth back to fifth. Get to little town 3 miles of hot stop and go at about 8600 ft. Stop for more errands twice. Stop at gas station which is the first time the cap has been off for two to three days. You know the rest of the story if you read the beginning.
Now, it has cooled and rained here a bit. I have not been all the way down to the city but running local errands which require much up and down I'm experiencing no signs of over pressure. It I'd Ob1 by the way. No lights. From what I read on verious other sites (the camero and corvette guys seem to have real issues here) this is "normal" for some systems. Scary as hell and likely pushing the edge of where no one wants to go but "normal" for some systems of the vintage given the gas we use today and extreme conditions.
That said, I do remember old timers ( in the old times) use to use about a pint or to per 10 to 15 gallon tank of diesel fuel to raise the boiling/flash point of the fuel mixture. Searching around it seems this solution is a rather common way to deal with the issue in Australia. I often think the Aussie's who seem to think simple and basic are way ahead of most of us here on many of these types of issue.

 

[renosauce]

Good thinking, I'm tending to the conclusion that I maxed out the system. Although, I'd like to clear up a couple of points. I start at about 8700 feet where I live. Always with a fullish tank because when you live where I live you get gas on the way home.
With about a gallon missing from the tank that's been sitting for day I head first up over the hill at about 9100 feet. Then down into traffic into the city at about 6000 feet. Parked for about an hour and a half in the hot sun (remember I started cool at altitude) so dispite the altuide drop things should already be expanding. Run errand in moderately heavy traffic very hot. Head up the hill in traffic so a lot of third and forth back to fifth. Get to little town 3 miles of hot stop and go at about 8600 ft. Stop for more errands twice. Stop at gas station which is the first time the cap has been off for two to three days. You know the rest of the story if you read the beginning.
Now, it has cooled and rained here a bit. I have not been all the way down to the city but running local errands which require much up and down I'm experiencing no signs of over pressure. It I'd Ob1 by the way. No lights. From what I read on verious other sites (the camero and corvette guys seem to have real issues here) this is "normal" for some systems. Scary as hell and likely pushing the edge of where no one wants to go but "normal" for some systems of the vintage given the gas we use today and extreme conditions.
That said, I do remember old timers ( in the old times) use to use about a pint or to per 10 to 15 gallon tank of diesel fuel to raise the boiling/flash point of the fuel mixture. Searching around it seems this solution is a rather common way to deal with the issue in Australia. I often think the Aussie's who seem to think simple and basic are way ahead of most of us here on many of these types of issue.

one thing you are missing is the expanding air inside your tank is actually compressing do to the ambient air outside.. as you decrease elevation.. the fumes and heat may expand to an extant but not as much as the air is actually compressing according to atmospheric pressure.. i am sure there is an exact number you can put on this.. but liken it to scuba diving... u dive down to 40ft.. you have to add more air to ur BCD to float.. if u start to swim up.. the air pressure actually increases or expands and makes you float even more.. that is causing you to dump air out of ur bcd.. so u don float up to fast..if you hold ur breath at 40ft then swim up you will explode..your lungs..since your tank can only let pressure in.. basically as u go down elevation ur tank equalizes.. but if you go up..you now have gas fumes/heat and major change in atmospheric pressure.. working against you and ur truck probably cant handle that much change in that short of time..if you let it sit over night after a drive and it still does it.. i would suspect you have an issue..


Blaaaahhhhhhhh

 

[Bob22222]

one thing you are missing is the expanding air inside your tank is actually compressing do to the ambient air outside.. as you decrease elevation.. the fumes and heat may expand to an extant but not as much as the air is actually compressing according to atmospheric pressure.. i am sure there is an exact number you can put on this.. but liken it to scuba diving... u dive down to 40ft.. you have to add more air to ur BCD to float.. if u start to swim up.. the air pressure actually increases or expands and makes you float even more.. that is causing you to dump air out of ur bcd.. so u don float up to fast..if you hold ur breath at 40ft then swim up you will explode..your lungs..since your tank can only let pressure in.. basically as u go down elevation ur tank equalizes.. but if you go up..you now have gas fumes/heat and major change in atmospheric pressure.. working against you and ur truck probably cant handle that much change in that short of time..if you let it sit over night after a drive and it still does it.. i would suspect you have an issue..


Blaaaahhhhhhhh

Right, the tank equalizes negative pressure. So once you down you pressure is "equalized" to that altitude. If you then go up it doesn't seem like it would matter what you did before you went down. Things boil at less pressure at higher altitudes as things turn to vapor the release pressure, correct.
I don't think the system was designed to operate on 10% alcohol fuel which has a significantly lower point of vaporization. That much (remember the fuel in the tank was at hard boil for minutes when I tried removing the cap) vapor sppears too much for system to handle.
Talking to the store manager and the guy who goes from station to station to check the pumps (he had a clip board, likes Toyotas, was not a government employee, and was charting number off each pump, said it happens more than you would think on very hot afternoons. The pump guy confirmed the diesel additive thing is rumored to work and "a lot" of companies operating at altitude use it in older equipment. I'm concerned about passage and sensor from and between the MAF and the catalic converter getting gummed though. Right now I'm just not using the truck in any conditions close to pushing the limit.
I think the deep water fish who has lived all his life at depth would experience the same blood oxygen issues as the diver if the fish came up to fast, but I could be all wet on that. But, I seem to remember so story...

 

[Bob22222]

Thinking about what I stated in the above post. I'd like to make it clear that the gas in the tank was no boiling until I "cracked" open the cap which release enough pressure to lower the ambient pressure of the fuel below its boiling point at the high temperature it was at. Thus, more proof the cap was doing its job of holding pressure. This one reason I shy from any thoughts of operating with a loose or vented cap.