Thinking you're completely out of gas while in the middle of nowhere is a terrifying thing. That very thing happened to me on my way to an event in October of 2014. I topped off my tank before heading out for the day. My fuel gauge looked like this.
It was beautiful out – warm weather, sunny skies, open roads – it was a great day. Fifty miles after leaving the gas station I was heading through some lovely area of Maryland en route to a cookout and, without warning, my fuel gauge looked like this.
My first thought was one of concern. Well, not so much concern as controlled panic. My buddy Chris was driving behind me in his Ford GT and my immediate thought was that I had just dumped all my gas out in front of him. I pulled off the road to check things out. There was nothing – no leaks, no smell of fuel, nothing. Chris didn't see anything wrong while behind me. The car was running just fine. So what was going on?
I went to the next gas station I found and filled up. It only took a few gallons, so there was still fuel in it. That meant the problem was in the fuel gauge. When Tim, my local Aston Martin Master Technician, got his hands on my car, he fixed it quickly and easily and, to my pleasant surprise, the parts needed weren't too expensive or hard to get. The issue was my fuel sending unit. He was surprised to see one fail so completely. He said that usually a sending unit will develop a small “dead spot” where the fuel gauge's needle stops working. For example, if the middle third of the gauge is the dead spot, the gauge will act normally for the top third, freeze at the 2/3-full mark, and then drop quickly to the 1/3-full mark once the gas level gets to that point in the tank, then act normally until empty or refilled.
Mine had gone binary. It was either full or empty with nothing in between.
The good news is that it was just the fuel gauge that was affected. The car itself ran fine and only the sending unit needed to be replaced. So if you find yourself driving along one day and notice your fuel level dropping inexplicably, it might be a simple fix. Just hope your sending unit doesn't go as bad as mine!