Topping of fuel tank may leave 2 gallons below max fuel capacity

[lucius]

When topping off fuel at a gas station, the fuel dispenser automatically stops when the fuel tank is full. The stopping mechanism works mechanically via venturi effect through a small additional opening in the nozzle, that starts sucking in fuel when the tank is full and thus stopping the fuel flow automatically. However, the fuel also causes foaming and the foam can have the same effect and shutting off the fuel dispenser. In all occurrences where the fuel dispenser stopped automatically, I was able to add more than two additional gallons of fuel until the tank was really full, by pulling the nozzle out and letting the fuel flow at a lower rate.
Two additional gallons is almost 10% (24.5 gal capacity for 200series), which is more than I expected. That additional 10% can be useful when optimizing for range, say when pulling a trailer and gas stations are spaced far apart, or one refuels at a very cheap gas station.

 

[04UZJ100]

……and can also damage the charcoal canister….

 

[lucius]

……and can also damage the charcoal canister….

Interesting. What charcoal canister and what is its purpose? Thank you!

 

[hoser]

Have you ever seen a fuel can swell in the heat? Where will that extra fuel go when your fuel heats up? It'll go into the charcoal canister and out of your pockets.

 

[lowenbrau]

P0445 code in 5…4…3…2..

 

[lucius]

Have you ever seen a fuel can swell in the heat? Where will that extra fuel go when your fuel heats up? It'll go into the charcoal canister and out of your pockets.

Sure, if you don't keep driving (road trip). For my knowledge, why does extra fuel not vent overboard and instead goes through a charcoal filter before exiting?

 

[hoser]

Emissions systems since the 1970's calls for a closed system to reduce the amount of hydrocarbons released into the atmosphere.

 

[isthatalexus]

……and can also damage the charcoal canister….

*Will

 

[Sandroad]

Even if you keep driving, the excess fuel vapors can’t vent properly if you’ve filled the tank fill tube by topping off. That messes up the canister too. Topping off is a bad thing to do. There are also many instances on Mud with raw fuel venting out the fill tube during elevation changes..

 

[isthatalexus]

What charcoal canister and what is its purpose.

Welcome home, brother. We're all happy to see you.

 

[lucius]

Even if you keep driving, the excess fuel vapors can’t vent properly if you’ve filled the tank fill tube by topping off. That messes up the canister too. Topping off is a bad thing to do. There are also many instances on Mud with raw fuel venting out the fill tube during elevation changes.

It does make sense, and I agree that liquid fuel should not enter the char coal canister and topping off may make this more likely. However, at it is explained that EVAP systems have usually a shut off valve that prevents liquid fuel to flow into the EVAP line and into the canister. If such valve would not exist, liquid fuel could enter the charcoal canister for other reasons even if not topped off. In other words, if topping of "will" damage the canister then it would also be damaged for other reasons.

 

[04UZJ100]

It does make sense, and I agree that liquid fuel should not enter the char coal canister and topping off may make this more likely. However, at it is explained that EVAP systems have usually a shut off valve that prevents liquid fuel to flow into the EVAP line and into the canister. If such valve would not exist, liquid fuel could enter the charcoal canister for other reasons even if not topped off. In other words, if topping of "will" damage the canister then it would also be damaged for other reasons.

You do you.

 

[Artie]

2 gallons is like 18 miles for me… not worth the risk IMHO.

If you want more range the LRA is the ticket.

Or maybe this thing?

 

[KLF]

I will also strongly echo the feedback about not attempting to squeeze every drop into the tank, it's a bad idea. The guy that does my annual inspections used to be a Master Tech at the biggest Toyota dealer around here, and he cautioned me years ago about not doing this. They had many charcoal canister replacements, most on 4Runners and Tundras. It's a very expensive repair.

 

[2021 LC200]

Sure, if you don't keep driving (road trip). For my knowledge, why does extra fuel not vent overboard and instead goes through a charcoal filter before exiting?

The charcoal canister filters out the gasoline vapor and sits above the spare wheel against the underside of the load floor/body. The filler neck sits 1 to 2 foot above that. There is supposedly a check valve to prevent liquid going up to the CC, yet that will pass slowly and probably due to ethanol fuel eventually stick and not close.

By topping off into the filler line the fuel will be pushing up that line and by repeat doing so will soak the CC in gasoline. Then things go downhill real fast.

Many of us know out of experience this is an issue and including folk like AMD who is an ex Toyota Master Technician now owning his own Toyota/Lexus specialist shop and who does excellent videos on all sorts of maintenance topics and repairs on T/L’s.

 

[ace10]

I saw a dude topping up his newer 4 runner the other day at sams club.
Like 20 extra clicks. No exaggeration.

 

[bloc]

Can’t fix stupid.

 

[2021 LC200]

When topping off fuel at a gas station, the fuel dispenser automatically stops when the fuel tank is full. The stopping mechanism works mechanically via venturi effect through a small additional opening in the nozzle, that starts sucking in fuel when the tank is full and thus stopping the fuel flow automatically. However, the fuel also causes foaming and the foam can have the same effect and shutting off the fuel dispenser. In all occurrences where the fuel dispenser stopped automatically, I was able to add more than two additional gallons of fuel until the tank was really full, by pulling the nozzle out and letting the fuel flow at a lower rate.
Two additional gallons is almost 10% (24.5 gal capacity for 200series), which is more than I expected. That additional 10% can be useful when optimizing for range, say when pulling a trailer and gas stations are spaced far apart, or one refuels at a very cheap gas station.

Is this a fill up from the computer showing near or zero miles to empty?

There is about 2 gallon of reserve gasoline which is past the zero miles to empty on our 200’s and probably the way it is done on all Toyota’s. This results in having about 21 to 22 gallon of fill up’s from “empty”.

Checking back it maybe more like 3 to 4 gallon of reserve fuel. See other thread about this.

Fuel tank capacity issue for MY16/17/18 Land Cruiser

forum.ih8mud.com

 

[Artie]

I saw a dude topping up his newer 4 runner the other day at sams club.
Like 20 extra clicks. No exaggeration.

That’s pretty bad. My worst example was watching someone top off until fuel came out of the filler neck on a late model Kia.

 

[hoser]

I saw a guy topping off his Prius at the gas station until fuel spilled out onto his foot. He was wearing open toed flip-flops.