Gas light - Toyota Nation Forum : Toyota Car and Truck Forums

Sfgsr1 · 03-01-2011, 07:26 PM

I was just wondering how much gas I have left once the gas light comes on? Thanks

pmesfun · 03-01-2011, 07:50 PM

In my experience(yes I have ran out of gas

) its about 2.5-3 gallons.

ThisBloodIsFake · 03-01-2011, 08:12 PM

I remember reading somewhere it was 5 gallons. which makes sense because Avi's have 18.5 gallons and every time i've ever filled up when the light was on i only put in 13 gallons or so.

pmesfun · 03-01-2011, 08:17 PM

^You're right, I was thinking when the needle was at the E line. The gas light on these cars are weird, mine comes on and off and back on when it gets low.

ThisBloodIsFake · 03-01-2011, 08:25 PM

haha i know right it always makes me laugh its the most indecisive idiot light i've ever seen

***84Cressida*** · 03-01-2011, 09:24 PM

It comes on and then goes off a few times to "warn" you, hence the name fuel level warning light.

I've never run out of gas, but I've been oh-so-close a few times with the light coming on numerous times and staying on with the needle right down to the E. I finally filled up and managed to shove in over 17 gallons and topped off without managing to overfill..so I was probably damn near close to bone dry

.

Sfgsr1 · 03-01-2011, 10:16 PM

Thanks for the quick replies now I know I won't run out going home tonight lol

skynet1988 · 03-02-2011, 11:49 PM

I noticed that when that light turns on seems that it is a function of the float that is in the gas tank. Leading me to believe that the fuel reading is analog, not digital. If you come to a quick stop with the fuel light on it will turn off the light!

ThisBloodIsFake · 03-03-2011, 08:32 AM

Quote:

Originally Posted by skynet1988

I noticed that when that light turns on seems that it is a function of the float that is in the gas tank. Leading me to believe that the fuel reading is analog, not digital. If you come to a quick stop with the fuel light on it will turn off the light!

Ya thats what we were saying i def. agree with that

Jigg007 · 03-03-2011, 02:23 PM

Quote:

Originally Posted by skynet1988

I noticed that when that light turns on seems that it is a function of the float that is in the gas tank. Leading me to believe that the fuel reading is analog, not digital. If you come to a quick stop with the fuel light on it will turn off the light!

Most, if not all cars have a float in the gas tank, which infers that all the sensors are of analog nature. the signal may be converted to digital in new cars, but ultimately is still a wishy-washy(bum-pish) sensor. The meters improved in newer cars because the way the computer interprets the sensor like so:

Ignore moderate fluctuations in a short amount of time, Average your readings and then update the gas gauge every 60 seconds or so. Allow drastic change such as a fill up so the gauge responds much quicker.

The mighty Avalon only smooths out and delays the values, so the gauge is open for some interpretation while the vehicle is changing direction.

However the superior way to measure gas in the car would involve a flow gauge on the filler tube. Measure how much gas goes in, and how much gas leaves though the fuel pump. That would be nearly pin point accurate, unless you have a hole in the tank (man I'm on fire!(double pun combo!!))

The poor mans way is to always fill up your car, reset the trip, and take an average of your MPG. Then if you're in a pinch simply divide your trip by your average mpg, and voila, gallons remaining in tank.

That was probably waaayy more than you wanted to read, but knowledge is power!

I've ran out of gas on a highway once, and coasted all the way to a gas pump.. I only realized I was out of gas when I reached for the key! Thats a really good way to burn up your fuel pump too because its running with no gas around it which acts as a heat sink, and to mention its sucking air!!

You have about 4-5 gallons in the tank when the light begins to fade in and out, and you're down to about 3 gallons or less when the light is solid lit.

***84Cressida*** · 03-03-2011, 03:26 PM

I'm assuming our cars have a fuel shut off program or something that cuts fuel when you're about to run out of gas so the pump doesn't burn out, yes?

Jigg007 · 03-03-2011, 04:27 PM

Quote:

Originally Posted by 84Cressida

I'm assuming our cars have a fuel shut off program or something that cuts fuel when you're about to run out of gas so the pump doesn't burn out, yes?

It has either a pressure switch or a timer, probably both. I know when the car is initially turned from the OFF position to the RUN (not started) It turns on the fuel pump for three seconds, and shuts off. Once the engine is running I would imagine the pump begins to run continuously. This next part is speculation of course, but once the engine sputters and dies from lack of gas, the timing/ignition system should also shut down and also turn off the fuel pump, returning it just like the initial OFF->RUN state.

... maybe

Chunkywolf · 03-04-2011, 07:50 AM

The fuel pump just runs to prime the fuel lines to 60PSI(most cars) when there are no injectors running. So, if the engine dies due to lack of fuel, The fuel pump will continue to pump until it reaches 60PSI(which it will probably never reach due to air getting in the line and such). I'm pretty sure fuel pressure is measured just above the pump, before the line exits the gas tank to head up to the engine compartment.