How does the gas pump nozzle turn itself off?
The basic concept of the automatic shut-off system has been around for 50 years, says Brad Baker of Husky Corp., a leading manufacturer of fuel delivery equipment. The next time you fill up, turn the gas nozzle over and look for a small hole at the tip of the spout. Now look inside the spout and notice there’s a tube inside leading from that hole. This tube connects the “sensing hole” at the nozzle tip to a diaphragm near a shut-off valve within the nozzle. Read: Tech Trends for 2010 — and Beyond When you squeeze the nozzle handle, gasoline pours through the spout and creates a vacuum in the small tube. This vacuum holds the diaphragm in a neutral position. When the fuel tank is nearly full, gasoline in the fill pipe rises and covers the nozzle-sensing hole. Air can no longer rush into the sensing hole to bleed off the vacuum, and the higher atmospheric pressure pushes the diaphragm up from the neutral position. This flips a switch in the automatic shut-off device and, ker-thunk, the p
