[galaxee]

your 82 chevy doesn't have an at-pzev rating. the hycam does.

this tank is far more effective at controlling evaporative emissions. the tank system is controlled by the hybrid ecu and is made of thicker steel to withstand a higher in-tank pressure. and it's a lot less inconvenient to the driver than that damned bladder tank they put in the prius.

from what i've read, california just wants there to be a lack of cracks in hoses associated with the fuel system, basically. not all california vehicles are required to have at-pzev rating, are they?

 

[hyperion]

The Prius tackles a small thing like driving a staple in with a six pound sledge hammer.
The door in the steel tank in the old truck closes so tight when the nozzel is removed that if you want to siphon any gas out of the tank you have to hold the sliding door open with an extra large screwdriver. (Ditto, with the Prius and Camry hybrid filler pipe.)
(It isn't the gas tank that prohibits the old Chevy from having the "at-pvev" rating!)
And my guess is that the Prius would have the same rating with a standard fuel tank right out of a new Corolla.

 

[Warthog]

Not sure about the bladder, but in almost all other vehicles topping off can result in fuel venting to the evap cannister, which is a fancy name for a charcoal filter that pulls the last remnants of fuel vapors out of the air vented from the fuel tank. Topping off can cause liquid fuel to drain to this canister, in most cases causing the "check engine" light to illuminate. (This light is now referred to as the "Malfunction Indicator Light" in all post 1990ish cars because it often refers to problems that aren't engine related). Most of the codes you'll see due to overfilling are emissions related (evap leaks, etc.). Beware, if you overfill and get fuel into the evap canister of any vehicle you'll likely fail an emissions test and it'll cost you a couple hundred bucks to replace the canister, even more if you have to pay a dealer to diagnose the problem and do the work for you.

 

[KTPhil]

I have always been able to pump another half to full gallon in after the initial shutoff. This is in Cali where the pump shutoff has a hair trigger as part of the pump vapor recovery system. This is tedious, since I can only get in a tenth or so with each squeeze. I don't usually bother unless I am taking a long trip, where driving range is a help to carefree touring.

 

[Pete44]

I was topping off to the very top (filler neck) every time for years. [Lexus CT200h....same system as Gen3 Prius] Then I got a P0441 code, which is "evap system" and I started reading about evap problems. In that reading there were people saying "never top off or gas gets into the evap system and wrecks your purge valve and/or your charcoal canister. Went to dealership and they diagnosed it was the purge valve. Replaced myself with OEM. No luck, kept getting code. Took it back to dealer....this time they said "bad charcoal canister", so I got one on eBay from a junk yard with "41k miles on it" (looked to be accurate from the appearance of the canister. Put that in. Don't recommend this....what a pain in the arse. Code off for a while....then back again. Took it back to the dealership. They said "Bad canister you bought" and were going to charge me close to $800 for a new canister (yes, after mis-diagnosing, and after causing me tons of hassle and grief). Anyway, I got a Lexus dealer to send them a brand-new OEM canister for half that price (or less, can't recall) and they put it in. All good for a while....then same code again.

This time, as they were responsible for all of it, I took it back and they happened to have a Lexus mechanic, who had run a large dealership maintenance department for many years, and happened to semi-retire in the small town in Colorado. This guy won't ever speak with customers...but he was willing to talk to me, once he saw how clean the engine bay was, how I had an oil catch can setup, and how I'd done a bunch of work myself. He found the problem...which nobody was going to find otherwise: Loose pin in the connector that has 20 pins and plugs into the computer that controls the purge valve. So the pin would sometimes activate the purge valve and sometimes not. He fixed it. No problems since. Super knowledgeable guy. Maintenance desk said, "He TALKED to you?! Was he ok to you?!?!" Apparently he has no patience for idiots but thought I wasn't one. (Got away with pretending to be an intelligent human for a few minutes).

Regardless, I'm now back to square one: My purge valve and charcoal canister were likely fine, after filling to the absolute brim, every time I'd fill up, for over seven years. So now I wonder all over again:

With the tank so annoyingly small, can I top it off without wrecking the evap system??? I absolutely hate how small the gas tank is. I fly airplanes and yes, I can go 5 hours without needing to pee. Large tanks allow for trips to take a lot less time by not having to stop. Currently, I'm commuting in my CT200h about 50 mins each way, at 78mph. (speed limit 75). This means that I get about two and a half round-trips before I have to fill up again. It's a pain to fill up every couple of days. Nuissance. Car gets about 35mpg (says 37.5, so I know it's right around 35) at 78mph. At 60 mph, I could get about 45mpg, but I'd be a friggin road hazard and drive everyone and myself crazy. Car just not made to go over about 65 efficiently.

Anyway, been following the guy trying to swap a corolla tank into a Gen3 Prius. Will have to read the rest of the forum, but it brings to mind:

1) With all the difficulties of swapping tanks (there are a lot of sensors, connectors, fitment issues, etc, etc), couldn't we just have a fuel cell with it's own pump mounted somewhere and have it pump fuel into the filler neck? That would seem to be an easy solution (and could be a completely sealed system, so could be mounted in spare tire well or something). I just would need to understand the evap system, where it pulls fumes from, where the vent is in the filler neck (seems to be right behind the small opening in the plate that blocks larger pump nozzles in the top of the filler neck).

2) Is it really a problem to top it off? Am I really going to damage my charcoal canister?

 

[nickie]

I was topping off to the very top (filler neck) every time for years. [Lexus CT200h....same system as Gen3 Prius] Then I got a P0441 code, which is "evap system" and I started reading about evap problems. In that reading there were people saying "never top off or gas gets into the evap system and wrecks your purge valve and/or your charcoal canister. Went to dealership and they diagnosed it was the purge valve. Replaced myself with OEM. No luck, kept getting code. Took it back to dealer....this time they said "bad charcoal canister", so I got one on eBay from a junk yard with "41k miles on it" (looked to be accurate from the appearance of the canister. Put that in. Don't recommend this....what a pain in the arse. Code off for a while....then back again. Took it back to the dealership. They said "Bad canister you bought" and were going to charge me close to $800 for a new canister (yes, after mis-diagnosing, and after causing me tons of hassle and grief). Anyway, I got a Lexus dealer to send them a brand-new OEM canister for half that price (or less, can't recall) and they put it in. All good for a while....then same code again.

This time, as they were responsible for all of it, I took it back and they happened to have a Lexus mechanic, who had run a large dealership maintenance department for many years, and happened to semi-retire in the small town in Colorado. This guy won't ever speak with customers...but he was willing to talk to me, once he saw how clean the engine bay was, how I had an oil catch can setup, and how I'd done a bunch of work myself. He found the problem...which nobody was going to find otherwise: Loose pin in the connector that has 20 pins and plugs into the computer that controls the purge valve. So the pin would sometimes activate the purge valve and sometimes not. He fixed it. No problems since. Super knowledgeable guy. Maintenance desk said, "He TALKED to you?! Was he ok to you?!?!" Apparently he has no patience for idiots but thought I wasn't one. (Got away with pretending to be an intelligent human for a few minutes).

Regardless, I'm now back to square one: My purge valve and charcoal canister were likely fine, after filling to the absolute brim, every time I'd fill up, for over seven years. So now I wonder all over again:

With the tank so annoyingly small, can I top it off without wrecking the evap system??? I absolutely hate how small the gas tank is. I fly airplanes and yes, I can go 5 hours without needing to pee. Large tanks allow for trips to take a lot less time by not having to stop. Currently, I'm commuting in my CT200h about 50 mins each way, at 78mph. (speed limit 75). This means that I get about two and a half round-trips before I have to fill up again. It's a pain to fill up every couple of days. Nuissance. Car gets about 35mpg (says 37.5, so I know it's right around 35) at 78mph. At 60 mph, I could get about 45mpg, but I'd be a friggin road hazard and drive everyone and myself crazy. Car just not made to go over about 65 efficiently.

Anyway, been following the guy trying to swap a corolla tank into a Gen3 Prius. Will have to read the rest of the forum, but it brings to mind:

1) With all the difficulties of swapping tanks (there are a lot of sensors, connectors, fitment issues, etc, etc), couldn't we just have a fuel cell with it's own pump mounted somewhere and have it pump fuel into the filler neck? That would seem to be an easy solution (and could be a completely sealed system, so could be mounted in spare tire well or something). I just would need to understand the evap system, where it pulls fumes from, where the vent is in the filler neck (seems to be right behind the small opening in the plate that blocks larger pump nozzles in the top of the filler neck).

2) Is it really a problem to top it off? Am I really going to damage my charcoal canister?

The owner's manual clearly states "Do not top off/overfill your gas tank."
I figure there must be a reason for this. Toyota doesn't waste type. I have never topped off my 12 year old Gen 3. Ever.
Why risk causing a major problem for a 1/2 cup more fuel? Why risk a nasty splash-back, and ruining a new suit, etc?