My Gen.2 -Now only holds 31/2 gallons of gas in the tank bladder

All sorts of plumbing/pressure/vacuum action going on in this system. I guess it follows that it isn't fully instrumented electronically.

Consider the mechanism within a gas station nozzle. Nothing electronic in its operation, yet lots of intricate logic mediated with tubes, balls, cones, springs, and diaphragms responding to gasoline and air flow.

After years of experience with the 2nd generation Toyota had the option of either adding electronic sensors and actuators to make it easier to control/diagnose the gas tank and evap system, or to go back to a regular gas tank without the bladder, and they chose the latter.

 

The automatic shut-off nozzle was apparently invented in Vancouver, named after the guy, the Seney Valve. My wife was doing home support for him. There maybe were others, collaborators or independents.

 

Compare and contrast, Japan vs. USA gas tank diagrams from Amayama (the year ranges overlap but are not identical):



There are actually two schemas for the USA model that differ slightly. The final schema for both countries seems to be the fuel line from the tank to the front and is virtually identical - the parts listed for that schema are the same but you can see that the routing of the tubes from the canister and fuel pump above the tank are a little different.

Not even the charcoal canister is the same part for both countries. 77740-47040 vs - 47050.

 

The ORVR system for gen 3 is a lot like gen 2, except for the bladderless tank. There still isn't a lot of instrumentation of the ORVR components, so it's still largely up to the human to diagnose issues.

 

Prius Hard to Fill Fuel Tank – Diagnostic Network

I don't have an account there, but it might be that the answer is available in one of the 3 blurred out replies if one does.

 

Finally decided to join the forum to share some info. I was able to swap the gas tank out for a carolla tank and just did a 100 mile test drive with mixed driving and no check engine lights or issues.

I'll be making a video and post of what I did after I get a full tank out of it to help others if they want to attempt the swap. It's not as easy as one would think. I'll say that.

 

I'm curious to know why you do this?

 

I knew it would go I'm just not sure about pressure sensor etc but getting it in they're seems to be a few that could strap in . I'd like to work in plastic unit . Easier to have custom fabbed too. But I'm making so many miles by the time I do this the car will be dead by well 600k or such . So I've not . But yes write it up pictures and year models for the parts or list.

 

Out of habit. Our state historically was one of two which mandated your gas must be pumped by an attendant. You'd pull up, wait a while until an attendant takes your card to activate and start the pump, they walk away, the pump stops, then you wait until they return to finish the process. They were paid by the hour and not by how many cars they filled. So I sat in the car and out of boredom kept the key in the on mode to make sure the fuel gauge go full before it finishes. I also log the mileage and the odometer display only worked in the on position.

 

Change the charcoal canister too? I've read that the one on the Prius is pretty small because the rubber bladder handles most of what the canister does on other cars.

I don't really understand in detail how the bladder decreases evaporation. It is always presented as "no air over the fuel to evaporate into", which makes some sense because one of the rate variables for evaporation is surface area at the gas/liquid interface. Molecule hits interface from liquid side and if it has enough energy it can break through into the gas phase, more area, more that happens. If there is no gas phase to break into, lower evaporation rate. However, some gas is eventually going to form above the liquid and it would seem like the bubble would just get bigger and bigger until the pressure increase from its expansion causes the evaporation to stop (or the tank vents or blows up). So the bladder is probably designed to let these bubbles rise to a vent and bleed off this small amount of gas through the canister. Also, the pressure inside the bladder could be higher than atmospheric (rubber container after all) and that would also reduce evaporation. Many conventional gas tanks seem to do something like that, since they hiss when the cap is removed.

 

I kept the original prius CC. I kept all the prius emission sensors. Only swapped the tank then made a vacuum tank to affix the "clean air" portion to. Stupid simple way to bypass the system when you don't over think it.

 

It is possible that the small CC may not be able to keep up with the evaporation from the Corolla tank in some circumstances. Like parked for several hot days in a row. It would presumably manifest the same way "CC cannot hold more gas" does on the car normally. Ironically one of those symptoms might be that it is hard to fill the tank.

All the hoses that went in/out of the tank other than those to the filler, to CC, to motor are routed to an empty sealed container? Sounds like it would work, the car would just "think" there was no evaporation going on (for some reason). What are the pressure requirements for such a tank?

Odds are the great state of California would refuse to register a car with this mod, even though it basically just turns the Prius into a Corolla, evap wise. They are really really picky about any modification that affects emissions.

 

My oil catch cans came with notice that they're not intended nor legal, for street use. They're closed-circuit, no venting through a filter. Just due to being a mod.

 

Kind of doubt there will be issues due to the"size difference". Kind of to my point with over thinking the system.

Vacuum or pressure requirements? Who knows and really can't be that much due to the sensors just being set into rubber seals. Used an old camping propane tank and cut holes for the sensors to mount. Used the same rubber seals to do this except for the temp sensor. Just used a press in style seal and put a bit of sealant around the sensor due to it being an oval shape. It's ghetto af but it works so far.

California emissions . That's all I'll say on that.

 

The state government loves to create bureaucratic nightmares, so of course the implementations of our emission laws are thick with that. On the other hand, when there are millions of people living in cities ringed in by mountains hoping the wind will just blow away the smog isn't wishful thinking, it is more of a death wish. I remember in the 1970's not being able to see mountains that were a mile away, and feeling like I had emphysema after a short run. Not just a day here or there, but for weeks or months at a time. CARB is a harsh mistress but that is the trade off for having clean air here. (It isn't just cars that are regulated, any source that puts junk in the air is a problem when said junk has nowhere to go.)

I am not at all convinced though that the difference in evaporative emission levels between a 2nd gen Prius and the same era Corolla is significant enough to classify changing the gas tank from one form to the other as "disabling emission controls". Try as I might, I have never been able to find the numbers for typical evaporative emission levels for either car. No data makes it hard to make a rigorous argument. Toyota itself tossed all the fancy evap controls for the next generation Prius, and one would assume that put it dead even with the corresponding next era Corolla. So how much better could it actually have been?

 

And that's to my point. I did the swap because I drive 160 min per day and got tired I filling up every 3 trip. Obviously the "greater emissions" bladder wasn't worth the squeeze because even Toyota ditched it. I can't think of a single good argument to keep the bladder.

I don't disagree with the principle of having better emissions for most vehicles. We do need to take better care of our air system but to what extent? They (the government and manufactures) are already lobbying to keep the average Joe from working on their cars on top of making emissions test that are near impossible to pass unless you're car is in immaculate and condition. The average person will turn around and buy a new car and get rid of their other one just because they can't get it to pass emissions or don't won't to hassle with it, which then causes more scrap and waste. It's a double-edged sword and you have to pick your poison.

At least that's the way I see it.

 

Googled this:

could gen 2 prius gas tank bladder been reinflated fully by applying air pressure to the tank

And AI thought it was a bad idea:

applying external air pressure can be dangerous and cause expensive damage to the fuel pump, bladder, or other EVAP components.

 

Lmao and then you have a pressurized fuel system to shoot fuel at you

 

Corolla fuel tank swap! It does work! | PriusChat

Link to the swap thread I will end up making.

 

Work with me, just like blowing air into mechanics/surgeons gloves before putting them on.