Why you can’t easily siphon gas from modern cars – Jalopnik

There may be times when you find yourself in a situation where you need to siphon fuel from your vehicle, either in an emergency or to remove the wrong fuel that was accidentally added. But it’s not as easy as it used to be, when you could just stick a hose into the fuel filler and almost poison yourself by sucking on it to keep the fuel flowing (yes, people really did that), or use a pump to drain the tank.

Modern vehicles come with built-in fuel failsafes to prevent thieves from making off with your gas. This includes some sort of mesh placed a bit in the filler neck, which prevents pipes from reaching the tank. If you get past that, you’ll have to deal with the anti-siphon valve. When an object pushes against the ball-like mechanism, the passage closes, but during a normal fill-up, the fuel flow moves the ball aside, allowing gas to enter the tank. This is also a safety feature that prevents fuel from escaping if the car rolls over.

While these safety mechanisms prevent thieves from siphoning gas through a pipe, some particularly clever mechanisms have gained traction by drilling holes in fuel tanks to steal gas. This has become yet another item on the laundry list of things stolen from car owners, one of the most common of which is catalytic converters.

If you have the right tools and knowledge to remove the gas tank, you can access the tank where the filler neck is connected and remove the fuel using a hose. Another method involves accessing the fuel rail in the engine compartment by removing the fuel system Schrader valve to draw fuel from the tank using the vehicle’s fuel pump. This works by redirecting the fuel flow, as the pump normally sends fuel from the tank to the engine when the ignition is on. You would have to do this a few times because the fuel pump will turn off if the engine is not started.

Removing fuel from the tank of a modern vehicle is difficult, not only because of the anti-siphon devices, but also because of their complicated fuel systems. They include one-way valves and internal barriers that ensure fuel flows in quickly during refueling, while preventing it from siphoning off.