How Does Your Fuel Gauge Work?

Published: 16th July 2009
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We all know we are running out of fuel when what happens? Yep, that little yellow light starts lighting up on the dashboard. Like Pavlov's dogs, we know it is time to fuel up, but how does our car know that it needs gas? Let's take a look.

The fuel tank warning light, or the yellow light of shame as I like to call it, is a reflection of the modern world. It is a bit of an insult. Think about it. The car designer thinks we are stupid enough that we have to be hit with a flashing yellow light to remind us not to run out of gas! If I hadn't run out of gas a few times in my old MG, I'd be outraged. Since I did, I'll just move along in this article!

How does your fuel gauge work? It sounds like a simple question and it is. The answer is also fairly simple. It has to do with the initial part of the fuel system of every car. As you well know, the fuel is stored in the gas tank. What most people don't realize is there is a mechanical device in the fuel tank - the fuel pump. As the name suggests, the fuel pump forces the fuel from the pump up the fuel line to the engine where it used in the combustion process.

The fuel pump is a multi-tasker. Sure it pumps fuel, but it also does much more. One of those tasks is to monitor the amount of fuel in the tank. It does this by using the simplest of measures. It has a sensor that is known as a float. As the name suggests, the float floats on the top of the fuel in the tank. The float is connected to a fuel sensor. This is braced on the fuel pump. As the fuel goes up or down, the sensor takes the readings and sends an electronic signal to your fuel gauge. It is that simple.

Since fuel is liquid, shouldn't the fuel gauge go up and down as the fuel sloshes around in the tank? Well, it does in older cars. If you drive or park on a hill, the fuel gauge would read less fuel in the tank. This doesn't usually happen in modern cars because the sensors are designed to average readings over a period of time. This makes for a more stable fuel gauge reading and lets you drive without worrying about running out of gas.

Your fuel gauge is something you look at all the time. Now you know how it actually works.

Dirk Gibson is with - where you can find high performance parts for your car or truck at low, low prices.

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