Q: How does the nozzle on a fuel pump know when to shut off to avoid overfilling the gas tank?

A: The next time you gas up, look for the small hole near the end of the pump’s metal nozzle. This hole becomes blocked by the liquid fuel as soon as the fill level reaches it. And blocking it with gasoline is what shuts off the valve.

There is actually a thin tube inside the main gasoline delivery hose that operates this valve system. That tube runs from the hole in the nozzle to a vacuum pump inside the gasolinepumping unit. While the pump is dispensing gasoline into a partially filled tank, air flows easily into the nozzle’s hole and the pressure inside the thin tube remains close to atmospheric pressure. But when the level of gasoline rises high enough, it essentially blocks the hole and the pressure inside the thin tube drops. This pressure drop is what triggers the valve and stops the gasoline flow.

For the Record

The world’s most valuable model car is a green 1937 Dinky Bentalls store delivery truck with yellow upper-side panels and a white roof. It was sold for US,148 at Christie’s in London in 1994.

There are only two others known to exist. Dinky Toys are die-cast miniature model cars and trucks. They first appeared in early 1934 when Meccano Ltd. of England, introduced a new line of "modeled miniatures" under the trade mark "Meccano Dinky Toys."

Past Track

January 15, 1936 — Henry Ford established the Ford Foundation, a philanthropic organization whose goals are to promote population control and to prevent famine; to support the arts and educational media; and to work for peace and the protection of the environment.

It was created partly to allow the Ford family to retain control of the Ford Motor Company after Henry Ford’s death, avoiding new inheritance laws. But its charitable works were very real. At its height, the Ford Foundation had assets of US billion.

Name Plate

Volvo: From the Latin word volvo, which means "I roll." Quite fitting, although it was originally the name for a ball bearing being developed by the Swedish company SKF. Volvo was founded in 1927 in the city of Gothenburg, Sweden, as a spin-off from SKF.