Fuel tank top off is bad. I'm now a believer.

Thanks for posting this information. Hope the fuel pump has lifetime reliability. Makes a good argument for purchasing an extended warranty.

 

OMG! What a complex system! I didn't realize there is a rubber seal around the gas pump nozzle when it's in the filler, that could explain some of the BGT (barfing gas tank) problems so many people have seen. Maybe when the bladder is full the gizmo in the top filler tube that's supposed to cut off the flow to the tank does not always work, thus BGT. I'm at one pip, definitely not going to overfill after reading that!

 

One of the important things that I'm reading here is that the car needs to be shut off when fueling! There are many who say since the ICE is not running, that there is no reason to shut it off. Yes there is. The operation of the fuel system is quite different if you fuel with the car on or off.

 

I am glad that I am reading all about this since I got my Prius. Topping off the tank has been my habit. Never in the Prius. Thanks for the great info on file.

 

it's been said here a thousand times, even evidence of real damage leading to gas tank replacement and people still think it's a myth?

ayyyy.

 

I for one believed it, nice to know why though.

 

Topping off isn't a familiar term to me except I read it often on PriusChat. I think it means filling until I see fuel in the filler neck, would that be right?

If this is right I think anyone who engages in this behaviour isn't thinking straight. Why risk damage to your cars paint just to squeeze in one or two more pints of petrol? In most American cars and SUVs you are talking an increase in range of what 4 miles if you squeeze in an extra quart! Whoop Dee Doo! Pointless.

 

This is correct. I'm going to mention it again, just in case it doesn't sink in right away. The valves in the fuel system reconfigure into a mode conducive to refueling when the Prius is shut down. When the Prius is powered up, the fuel system is not ready to accept more fuel. It can't be much simpler than that.

Tom

 

Tom, maybe that explains all the complaints, "I can't fit more that X (smaller than expected) gallons in my tank even though the last pip is flashing." posts we see on here from time to time?

It may be because people are ignoring the handbook and the law when filling up.

 

It's also interesting to note that the gas gauge may become inaccurate due to extreme slopes, especially when refilling. I don't know of any gas stations that aren't level, but resetting the inclinometers may help some folks.

 

thank you so much for the post!!

now will it make a difference??

it has obviously converted a few of you, but many have preached for years not to top off or refuel while the vehicle is on...(the fact that both are either against the law or strongly cautioned against apparently meant nothing)

this should be a sticky and an addition to the KB

 

PM one of the mods... but i venture to say, they are already in the process of doing so. may need to look at the source to determine if any legal issues are involved.

 

Awhile back, there was someone here in another thread who has 60K+ miles on his Prius(it's not me, I only have ~13K) that has topped off every time without any of these described problems. I am not doubting in any way that these problems won't occur, I'm just trying to understand how someone could top off for over 60K miles and why they have not had a problem; are they doing something different? By the way, I did save the PDF file to my computer for future reference. It is very informative and does a good job of describing why topping off isn't recommended.

 

That might have been me. I did mention it in the past. I have just passed 60,000 miles and routinely 'top off' the tank. I don't keep filling it until the fuel is level at the top, but I usually can easily put in 1 gallon with the nozzle not inserted all the way into the nozzle after the first click off of the nozzle. I have yet to throw any codes from the Prius computer.

Yes I read the original pdf and it does state problems can occur when topping off in the fashion I described.

But perhaps it is more likely to happen if fuel is forced into the tank (fuel nozzle shut off failure) or the tank it topped off when the Prius is left ON during refueling.

In any case the pdf has left me wary of even topping off the tank as I have done in the past. I suppose I will now just fill the tank when the nozzle clicks off by itself and leave it at that. I will, though, forgo the extra 50 or so extra miles of range I have been able to achieve with each tank by 'topping' it off.

I was surprised to read in the pdf that if any fuel is present outside the bladder in the tank to replace the entire unit. That I assume would be absurdly expensive.

As with the previous thread about the batteries, I think Toyota has cut corners allowing the system to be easily damaged by habits which many consumers use on other automobiles with no problems.

The fuel system could have been designed so it would be virtually impossible to damage from overfilling, but apparently it hasn't.

Rick
#4 2006

 

i applaud Toyota and the excellent fuel storage system...

and although you feel that Toyota dropped the ball by "allowing" us to possibly damage the system, i think their #1 concern, reducing further damage to the ecosystem is a much more important issue than catering to someone who continuously goes against recommended procedures.

obtw... do you feel the same way about drunk drivers?... "allowing" them to drive drunk?