I was curious as to how much fuel one can normally continue to pump into the Gen III Prius to top off the tank after the typical gas pump release stop. It seems I can only add just a tad more with the gas pump continually wanting to stop. Tempted to add more but don't want to see fuel spilling out of the tank.
In addition to fuel spilling out the top, you run the risk of saturating the charcoal canister that's part of the emission control system. As a result of learning about that and the onboard refueling vapor recovery system that's been in the last several vehicles I've owned, I don't top off, even to round up to the nearest nickel.
I pumped on the lowest setting with the pump engaged at the lowest detent on the pump handle. When the pump clicked off I managed nearly 2.4 gallons of gas into the tank before the fuel level was at the top of the neck and you could not get another drop in. This well increase your range well over 100 miles. I only did this once because in Oregon you can not pump your own gas, and would not do it on a regular basis unless I needed the extra range. alfon
Topping off fuel tank just recently became illegal in Oregon; attendant can pump more fuel to get to the next whole dollar w/ your permission.
That's good. One of my early bad experiences with OR pump attendants was the guy who ignored my explicit instructions to not top off, and kept clicking until fuel gushed all over the side of the car. After a couple more bozos, I learned to avoid or minimize refills there.
NJ is the same way. I heard rumors it was because of the average IQ in those states but of course I don't believe that.
There's a Gen II vs Gen III top-off difference. On my Gen II, I could always squeeze in an extra 2.0 gallons without a spill after the first click; I did this for 3 1/2 years and never had a charcoal canister problem. It was just a function of the bladder design. On my Gen III, first click and that's it. At 0.2 gallons after the click, I'm wearing fuel on the side of my car; not worth squeezing anything extra in. Maybe there's a pump click diference between the States/Brands. I could never squeeze in more than the 0.2 gallons in my Gen III. Alfon, I'm amazed at your extra 2.4 gallons; I'm going to give it a try again the next time it's raining hard and the over-spill won't hurt my paint as much.
It may not have failed in that time, but it was unlikely that it was doing its job... since it was probably contaminated from gas saturation. .
Some pumps are very sensitive and switch off way before the tank is full. It happens quite regularly that it clicks off after only 5 or 10 litres. 2.4 gallons is too much for a normal click off. Getting in 2 more litres after the first click off seems more normal to me. That is what you would expect the extra length of filler tube to hold: 2 litres, not 2 gallons.
At what point do you risk causing damage to the canister? For years I've filled my tank until the pump clicked off, waited a few seconds, then squeezed the pump until it clicked off again. Usually an extra half gallon or so goes in, but sometimes a lot more (which is the main reason I do it). Never has the tank overflowed. If I'm only going to the second click I'm I likely to cause problems? (This is the first time I've even heard of a potential problem other than getting gas on the outside of the car.)
You risk it at any point. Pumps were designed to click off for a reason. Remember, gas expands and contracts depending on the outside temp so if you overfill it, live in a hot area, well you are doing damage to the car, you just don't know it. Don't Top Off Your Gas Tank! | Mid-Atlantic Air Protection
