pumping gas

[DecoyOctopus]

i was just filling up this morning and it hit me...how does the darn thing know when my tank is full?!?!?!?!?!?! does anyone know?

[stillaneon]

i was just filling up this morning and it hit me...how does the darn thing know when my tank is full?!?!?!?!?!?! does anyone know?

In a gas pump handle you have two valves: the main valve, which is actuated by the oversize trigger you squeeze to make the gas flow, and the check valve, which lets gas flow out but won't let anything back in again, thus reducing fire hazard. In the seat of the check valve you have a little hole. To the backside of this hole is connected a Y-shaped tube. One branch of this tube runs down the nozzle and exits at the tip while the other runs back to a diaphragm connected to a release mechanism on the main valve. When you squeeze the gas pump trigger, gas running past the hole in the check valve sucks air out of the Y-shaped tube. (This is because of the Bernoulli principle: a moving stream of fluid tends to pull things in from the sides. Take my word for it.) As long the end of the Y-shaped tube exiting at the spout is unobstructed, air is simply pulled into the tube and nothing much else happens. However, as soon as the gas in your car's fill-up pipe gets high enough to cover the end of the tube, a partial vacuum is created therein, which yanks on the diaphragm, releases the main valve, and shuts off the gas. If the gas happens to be especially foamy one day, it may actuate the release mechanism prematurely, with the result that you end up with less than a full tank of gas.

Dont know if it made any sense but there it is

[speedminded]

Next time you're at the pump look for the small hole at the end of the nozzle. There's a tube from that hole up to a mechanism on the trigger that detects air pressure. When your fuel tank is empty it's full of air, just like pushing down on a gravity bong, air is forced out as you fill the tank with fuel...when the fuel gets to the top (or water in the case of a gravity bong) there is no more air coming out. When the mechanism detects no more air pressure it flips the nozzle to stop the gas from pumping.

[JITB]

In a gas pump handle you have two valves: the main valve, which is actuated by the oversize trigger you squeeze to make the gas flow, and the check valve, which lets gas flow out but won't let anything back in again, thus reducing fire hazard. In the seat of the check valve you have a little hole. To the backside of this hole is connected a Y-shaped tube. One branch of this tube runs down the nozzle and exits at the tip while the other runs back to a diaphragm connected to a release mechanism on the main valve. When you squeeze the gas pump trigger, gas running past the hole in the check valve sucks air out of the Y-shaped tube. (This is because of the Bernoulli principle: a moving stream of fluid tends to pull things in from the sides. Take my word for it.) As long the end of the Y-shaped tube exiting at the spout is unobstructed, air is simply pulled into the tube and nothing much else happens. However, as soon as the gas in your car's fill-up pipe gets high enough to cover the end of the tube, a partial vacuum is created therein, which yanks on the diaphragm, releases the main valve, and shuts off the gas. If the gas happens to be especially foamy one day, it may actuate the release mechanism prematurely, with the result that you end up with less than a full tank of gas.

Dont know if it made any sense but there it is

wow so thats what happens when the god dam handle wont hold and keeps stopping... the gas is too foamy?

[IDCoconut]

^ No, that means gas is getting stopped on the way to the tank and is backing up. As you know, re-arranging the nozzle to where you have a less restrictive flow will fix this.

that or your tank is full.

[DecoyOctopus]

so thats how it works

[.blank cd]

yes. Those nozzles should be on all stage2 systems, which are at all BPs and QTs. Keep in mind when it cuts off, 99.9% of the time your tank is full, so when you keep clickin on the handle when it stops, gas is gettin sucked down that little valve and the station is reaping the benifits. It kills me when i see people doin that

[EM1toEVO]

Thanks for the detailed explanation.

[DecoyOctopus]

yes. Those nozzles should be on all stage2 systems, which are at all BPs and QTs. Keep in mind when it cuts off, 99.9% of the time your tank is full, so when you keep clickin on the handle when it stops, gas is gettin sucked down that little valve and the station is reaping the benifits. It kills me when i see people doin that

no ****ing way!!!!!!!!!!!!!! i always ****ing do that!!!!!!!!!!!!!! wow i feel...used.

[Schugg]

no ****ing way!!!!!!!!!!!!!! i always ****ing do that!!!!!!!!!!!!!! wow i feel...used.

haha no need to flip out, it may do that, but seriously, the gas station is not getting and benifits out of it worth worrying about. it suck up like .015 cents of gas......so

i guess when your 80 years old and have done that your whole life you may have lost a few hundred dollars. if that

[SixSquared]

Is it bad that I "top off" my tank not because I want a really genuinely super full tank, but because I'm lazy and am rounding it to the next dollar so it's easier for me to balance my checkbook?

And while some of the gas may be going up that thing, is all of it? Cause I know in my quest to have $27 instead of $26.43, I have overflowed many a time. >_>

[speedminded]

yes. Those nozzles should be on all stage2 systems, which are at all BPs and QTs. Keep in mind when it cuts off, 99.9% of the time your tank is full, so when you keep clickin on the handle when it stops, gas is gettin sucked down that little valve and the station is reaping the benifits. It kills me when i see people doin that

haha no need to flip out, it may do that, but seriously, the gas station is not getting and benifits out of it worth worrying about. it suck up like .015 cents of gas......so

i guess when your 80 years old and have done that your whole life you may have lost a few hundred dollars. if that

Is it bad that I "top off" my tank not because I want a really genuinely super full tank, but because I'm lazy and am rounding it to the next dollar so it's easier for me to balance my checkbook?

And while some of the gas may be going up that thing, is all of it? Cause I know in my quest to have $27 instead of $26.43, I have overflowed many a time. >_>

It doesn't suck anything up, it's not a vacuum, and it doesn't magically work against the worlds gravity...ZERO fuel is lost (unless you fill it past your overfill drain anyways).

It merely measures the air pressure that is being forced out of your tank as you fill it with fuel. You have the choice of two things in your tank, gas or air, the more fuel you put in it the more air that is being pushed out. When you fill your tank there is no more air to be pushed out therefore it knows when to stop because that air pressure is now gone.

[1CleanEg]

definitely interesting stuff in this thread.

[.blank cd]

It doesn't suck anything up, it's not a vacuum, and it doesn't magically work against the worlds gravity...ZERO fuel is lost (unless you fill it past your overfill drain anyways).

It merely measures the air pressure that is being forced out of your tank as you fill it with fuel. You have the choice of two things in your tank, gas or air, the more fuel you put in it the more air that is being pushed out. When you fill your tank there is no more air to be pushed out therefore it knows when to stop because that air pressure is now gone.

This is what i was told by BP. You might have been informed on stage 1 vapor recovery, but theres recently been a change

[.blank cd]

...And while we're on the subject of pumping gas, please tell your friends and family its not cool to set your auto shut off nozzle and walk inside the store. Its not "fail-proof" and sometimes (rarely) it doesnt shut off. I hate telling people we're not resposible for all the gas thats on the ground after they go inside. BP is allowed to shut off your pump if we catch you. same goes for yall who think its cool to leave your car running while fueling. we can shut it off for that too. there are reported cases of pumps catching fire. they dont have this stuff posted all over the pumps for no reason

[EK Hotch]

That was beautiful....period.

In a gas pump handle you have two valves: the main valve, which is actuated by the oversize trigger you squeeze to make the gas flow, and the check valve, which lets gas flow out but won't let anything back in again, thus reducing fire hazard. In the seat of the check valve you have a little hole. To the backside of this hole is connected a Y-shaped tube. One branch of this tube runs down the nozzle and exits at the tip while the other runs back to a diaphragm connected to a release mechanism on the main valve. When you squeeze the gas pump trigger, gas running past the hole in the check valve sucks air out of the Y-shaped tube. (This is because of the Bernoulli principle: a moving stream of fluid tends to pull things in from the sides. Take my word for it.) As long the end of the Y-shaped tube exiting at the spout is unobstructed, air is simply pulled into the tube and nothing much else happens. However, as soon as the gas in your car's fill-up pipe gets high enough to cover the end of the tube, a partial vacuum is created therein, which yanks on the diaphragm, releases the main valve, and shuts off the gas. If the gas happens to be especially foamy one day, it may actuate the release mechanism prematurely, with the result that you end up with less than a full tank of gas.

Dont know if it made any sense but there it is