Will running the gas tank too low cause damage to the electric fuel pump?

You're over-worried. If what you described is accurate, there would be tens of thousands of vehicles sitting on the side of the road with dead fuel pumps. The engineers know driving with a low fuel level is a normal condition.

There IS some truth to what you were told, but there's more to the story. Ford, for example, was worried enough that as far back as the early 1990s, when their fuel gauges read, "empty", there was still four to seven gallons in the tank. There's something different to be aware of. What happens when you go up a steep hill or go around a corner when the fuel level is low? The remaining fuel would run to one side of the tank, away from the pickup tube. Even a brief instant of sucking up air would cause engine stalling. That is obviously not an acceptable condition. In the case of my Grand Caravans, there is a bowl in the middle of the tank that the fuel pump sits in. A real lot of fuel gets pumped to the engine, then the majority of it goes through the pressure regulator, then back into the tank. That returning fuel flows forcefully up a ramp around that bowl, and the flow pulls in additional fuel to keep that bowl full. As long as that bowl remains full, the level can safely drop to the last half gallon. The pump is still sitting in fuel to cool it. Regardless of driving maneuvers, the pickup tube always has a supply of fuel.

One note to be aware of is what you must do if you DO run out of fuel. In the case of my '88 Grand Caravan, fuel that is poured in from a can dumps directly into that bowl, so a quart is plenty to get the engine restarted. You may need to cycle the ignition switch from "off" to " run" two or three times because the pump only runs for one second until the Engine Computer sees the engine is rotating, (cranking or running). One cycle might not be enough time for the pump to prime and get the fuel up to the needed pressure. For my '94 and '95 Caravans, the fuel misses the bowl and goes right into the tank. It takes up to five gallons before the level is high enough to spill into the bowl, then the engine can be restarted. While it takes up to five gallons to get the engine to start, at that pint you can use up the entire five gallons. The bowl will be kept full once the engine is running.

Also be aware fuel pumps fail in different ways. The two I'm most familiar with are GM and Chrysler pumps. GM fuel pumps almost always start up, then they slow down or quit while you're driving. That leaves you sitting on the side of the road. Explanations I've heard include bearings in the motor that become tight, and housings that warp over time causing the armature to drag. Often those stalled pumps will run for a while after cooling down for a couple of hours.

Chrysler pumps most commonly fail by failing to start up, leaving you sitting in the driveway or parking lot. This happens at higher mileages and is due to worn brushes in the motor. Banging on the bottom of the gas tank often gets them started. The jarring makes just enough of a connection to start the armature rotating. From then on, it will stay running until the engine is stopped. This always starts out as an intermittent problem. It could fail to start up the next time, or it might not act up again for many months.

I don't know the history for other manufacturers, but there are none known with unusually high failure rates that I'm aware of.

Happy to help. While we're on the topic, the question sometimes comes up about why the normal sparking at the brushes doesn't cause an explosion. (As though you need something more to worry about). The fact is the gas fumes create an excessively rich mixture that can't burn without oxygen, even when the tank is empty. That should come in handy at your next trivia contest.

Please come back to see us with your next concern.

The explosions you're talking about aren't caused by the running fuel pump. There's two things we worry about. During filling, there's fumes leaving the tank. IF those fumes linger in the area, and IF you have a less than perfect seal on a spark plug boot, it's possible an errant spark COULD ignite those fumes. That's a lot of "ifs", and you'd hear about it every day on the news if it was a common occurrence.

The more common, (although still very rare), is the engine is stopped during filling, but the driver slides into the seat to retrieve something, then, as they slide out, they generate static electricity that ignites those fumes. That static electricity is a very real concern when we're working with air bags. For demonstration purposes, we can light off an air bag with a 9-volt transistor battery. When you can feel a static shock after walking across a carpeted floor and touching a door knob, or when grabbing a door handle after sliding off the front seat, that has to be at least 3,000 volts before you'll feel it and / or see the spark. By the way, it also takes some effort to accidentally fire an air bag. Safety features have to be purposely disabled.

The same thing occurs when filling a plastic gas can. Static electricity develops when the can is slid across a plastic truck box liner. Pump nozzles are grounded, so when they're touched to the can, a spark occurs when the static electricity is discharged. That can ignite the fumes. To prevent that, we're told to place the can on the ground.

Be aware too you will never sleep again if you watch all the stunts on Hollywood tv shows. It seems every car that leaves the ground or bumps into another one has to explode furiously. In reality, it takes quite a bit to make a tank of gas explode. Even in the videos of fumes being ignited at gas stations, if you watch closely, there is rarely an explosion. Rather, just like inside the engine, the gas burns very rapidly. One woman in particular had the presence of mind to simply close the fuel door on her car, then stand there and wait a few seconds for the flames to go out.

You can drive yourself to extinction worrying about all the hazards that rarely occur. If you think sitting on top of many gallons of a highly explosive liquid, (gasoline) is dangerous, imagine sitting right next to hundreds of volts of battery power capable of very high current, in an electric car. With alternating current in house wiring, you can let go if you get a shock. With direct current in cars, your muscles will not allow you to let go. That's why fiberglass poles in repair shops are a required tool, so a coworker who is lucky enough to see someone being electrocuted can run over, find the pole, and hopefully pull you away without getting shocked himself. I'll stick with gasoline for now. Any scenario you can think of has had some type of safety prevention designed in. In fact, gas tanks are so safe, we've become complacent and don't think about it enough.