fuel sensor
fuel sensor
(OP)
Hi all I am new in this forum.
I have a question about how it works when one is fuelling a car at the gas station.
How does the pump know that the tank is filled ?
Could somebody help me with this ?
Kindest regards,
atlaskar1
I have a question about how it works when one is fuelling a car at the gas station.
How does the pump know that the tank is filled ?
Could somebody help me with this ?
Kindest regards,
atlaskar1





RE: fuel sensor
Blacksmith
RE: fuel sensor
The fuel tank has a dip tube which keeps a void at the top of the tank (~10% vapour space). This is important since the fuel is pumped in cold from an underground tank, and can then sit in the vehicle tank and get hot in the sun. Without the compressible expansion volume the tank could split with hydraulic pressure.
When the tank is full the fuel starts to come up the filler neck and the pump nozzle detects the back pressure and clicks off (the sensor in the nozzle is down the small pipe that you can see below the main nozzle).
RE: fuel sensor
I needed a good laugh to start the day
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: fuel sensor
Could you perhaps point me to a picture of this ?
i am a little bit confused about how to detect backpressure...
Allow me to think loud:
The fuel comes into the tank with a certain pressure which could be detected by a simple manometer.
Are you saying that one needs to detect a decrease in pressure from the manometer ?
And if this is what you mean, do you know any "hard and fast method" to estimate this backpressure ?
Regards,
atlaskar
RE: fuel sensor
RE: fuel sensor
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: fuel sensor
These travel back up that small tube creating a psychic resonance. That is the sudden shock you feel when the fuel shuts off.
RE: fuel sensor
Sometimes you here people complain that the pump keeps shutting off, that can be caused by two things. If the end of the pump nozzle is damaged the fuel won't flow out smoothly and may splash around in the filler neck and cover the sensing port long enough to move the diaphram. Another common cause is that the cars fuel vent tube, rollover valve, or evap cansiter is restricted which allows pressure to build up in the tank and causes fuel to rush back up the filler neck and cover the sensor port shutting off the pump.
-Jon
RE: fuel sensor
I am giving you a star. While I, too, as a typically curious engineer as to how things work, had always wondered what was the mechanism that shut off (or not) the pump nozzle, I found it curious that among such a group of such brains, it took this long to get to the bottom of this mystery.
Thanks for enhancing the knowledge base of this group.
rmw
RE: fuel sensor
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: fuel sensor