What Happens When Your Car Runs Out of Gas?

All of us who have driven for a while have running-out-of-gas stories. Either a friend or family member ran out of gas at an inauspicious time or you had that very unpleasant experience yourself. Here's my friend or family story: on a double date with my brother and two very nice young women we ran out of gas in the line to get into a drive-in movie theater. Since the show was about to start and there was a long queue of cars behind us, the problem didn't make my brother — or any of us in the car — too popular. 

what happens when a car runs out of gas

On a more personal note, I used to work for a car magazine editor who insisted on driving the cars he was testing until the gas tank was virtually empty and then passing the car off to one of his underlings, like me, to fill it up. On one occasion the car he'd passed off to me ran out of gas less than 100 yards from where he had left it for me. The good news? A gas station was just another 100 or so yards away … and it was downhill. While this story had a quick and happy ending what happens when you run out of gas typically doesn't end nearly as well. 

What Happens from Behind the Wheel

You might surmise that when your car runs out of gas the engine simply stops running, but it typically doesn't happen that way. Most often the car will show signs of "fuel starvation" that include engine sputter, intermittent power surges, and perhaps even engine backfires. You will certainly notice a loss in power, and that is your indication to make your way, as safely and calmly as you can, to the right shoulder as far off the road surface as you can safely go.

This process will be made more challenging by the fact that when your engine dies, hydraulic power to your brakes and steering die with it. That doesn't mean that you can't steer or stop the car. It simply means that braking and steering will require additional effort. 

If you are driving a car with electric power steering, you'll be in luck because the electric power-assist will continue to function as long as there is power in your car's battery. Electric power steering might be a feature you look for as you use a car finder to compare cars

What Happens Mechanically

Though the loss of engine power causes hydraulic assist for the steering and brakes to cease, it won't cause damage to those components. But running out of gas still could damage your car, and it might result in the necessity of a very costly repair. 

The reason? When you run out of gas it can play havoc with your fuel delivery system. Here is what can go wrong. If you are driving a modern car it is almost certainly equipped with an electric fuel pump that resides in your car's gas tank. That fuel pump uses the gasoline in the tank to both cool and lubricate itself. As your fuel supply diminishes there is less gasoline in the tank to perform these vital functions. With only a minimal amount of gas in the tank, the fuel pump is very likely to overheat and fail. That is an expensive fix itself, but it could be worse if, during its process of self-destructing, the fuel pump sheds debris that gets into your car's fuel system. 

Problems Running Out of Gas Can Cause

Virtually all cars have fuel filters designed to catch debris, scum, and sediment before it gets to the engine's fuel injectors. If your failing fuel pump is shedding debris, it is likely that debris will clog the fuel filter. 

Even if the fuel pump remains intact, it is possible it will suck sediment that has collected at the bottom of the gasoline tank into the fuel line, and that can clog the fuel filter or, even worse, find its way into one or more of the fuel injectors, clogging them. All this will make it difficult to re-start your car and keep it running after you add more gasoline to the gas tank.

A new fuel filter is a relatively easy and inexpensive fix, but repairing or replacing clogged fuel injectors is a much more difficult and expensive proposition. You might be able to replace the fuel filter by the side of the road, but clogged fuel injectors will require a tow and a costly repair.

Even if no debris or sediment gets into your fuel line when you run out of gas there is the likelihood that if your fuel pump is drawing from an empty tank. That means air will get into the fuel line, and that needs to be bled off before your car will start and run properly again.

What You Should Do if Your Car Runs Out of Gas

Now understanding what happens when your car runs out of gas, you certainly understand what it suggests. You need to safely stop the car as soon as you can.

If you sense that your car is acting as if it is running out of gas by sputtering and seeming to "miss," first quickly confirm your suspicions by checking the fuel gauge and noticing if a low-fuel indicator light is glowing. Then make your way safely to the shoulder of the road as far away from traffic as is practical. You should do this as quickly as is safe because you want to overtax the fuel pump as little as possible and prevent as much debris as possible from being sucked into the fuel system. When you are parked, turn off the ignition, turn on your emergency flashers, and then consider your alternatives.

You might be close enough to a gasoline station to walk there and return with a gas can full of gas. If that's the case you might get out of your predicament suffering little more than some embarrassment and unexpected exercise. 

Should getting fuel yourself not be practical or safe, a call to your auto club, roadside-assistance provider, or a nearby gasoline station is your next step. If your car is off the highway, it is typically safest to wait for assistance inside your car rather than outside it.

If you have diagnosed the situation and responded in time, it is very likely that after putting gasoline into your car's tank, you'll be able to start the car's engine and be on your way. If the engine is difficult or impossible to start or if it fails to run smoothly after a few minutes of idling, you are well-advised to have your car towed to a technician who can diagnose the problem and make repairs.

An Ounce of Prevention

Of course, you can prevent all of the problems detailed here simply by making certain you never come close to running out of gas. It shouldn't be news to you that running out of gas is something to avoid, and one good way to do that is by filling your fuel tank every time it dips to the quarter-tank mark. That way you can keep your current car running great, and you won't need a car loan calculator to help figure out how much you need to spend on a new set of wheels.