Did I clean my fuel system by running out of gas?

I have a 99 Explorer. Over the past couple months I noticed my car was not starting very well, and it was slowly getting worse. I figured it was from the cheap gas I buy at BJ’s wholesale store. I tried out a bottle of fuel system cleaner, and it made a big improvement, but it still has had a bit of a lag in the start up.

Yesterday, I drove to work with the gas meter below E. After years of letting it dip below, I’ve got a good feel on how far I can push it, and amazingly I have never run out of gas before. However, on this day I parked in a spot that was angled so my car was facing downhill. Anytime the car is angled this way the meter goes way down.

So I am going to lunch and the car is not starting. I tried several times to get it going, letting rev for around 5 seconds each time. No luck… I took a walk and got some gas, and the car started right up.

Since this happened, my car is doing great. It starts right up, and sounds good. Did I accidentally do something good for my car?

Running out of gas is never good for the fuel pump. About the only scenario I can envision is you have some accumulated crud in the gas tank. The fuel pump pickup has a filter on it commonly referred to as a sock. If the sock was plugged with debris, it might have dried up and flaked off of it while it was exposed. The cleaner may have helped rid the sock of some of the gum accumulation along with cleaning out the injectors. If that’s the case, it’s only a matter of time before the problem returns.

I’d replace the fuel filter immediately. Then, if the problem returns, do a fuel pump pressure and volume test to see if it is running within specifications.

Running out of gas is never good for the fuel pump.

While I agree with all of Twin’s comments, this one needs repeating. Don’t try to run your tank that low. It can cost you in the long run. Let’s face it, it does not cost more to fill the tank sooner.

Agree! We have had several posts on this before; today’s fuel pumps are sensitive to overheating, since they are cooled by the gas in the tank, and constantly recircultate the gas to the injection system.

You were lucky nothing bad happened to the pump this time.

Running a vehicle out of gas can damage the fuel pump, which usually uses the fuel in the tank as lubricant and coolant. When is the last time you changed the fuel filter?

The gas sold at BJ’s and other discount wholesalers is as good as the gas sold at other stations. The next time you have a problem, I recommend you disgnose it rather than quess at the cause.

We need Myth Busters on this statement that, “Running out of fuel will cause the fuel pump to overheat (or, wear excessively, or have accelerated self-destruction.”

Actually, I don’t think so. Follow the chain of events: 1. Cooling flow of fuel ceases flowing from fuel pump (fuel depletion). 2. Fuel pressure falls to below engine sustainability. 3. Engine dies from lack of fuel. 4. With no signals to the engine computer, the computer de-energises electrical power to fuel pump. 5. Fuel pump ceases to run from lack of electrical power. 6. Vehicle stops after bleed-off of momentum and gravitational acceleration forces, if any.

When was the fuel pump damaged? Do you have proof, or just conjecture? Don’t pay attention to the voice behind the curtain!

I suppose you have a point, but most people will try to restart their car when they run out of gas, in which case the pump will try to rebuild pressure and will be run dry. Also, when you do run out of gas, gunk gets into the fuel pickup, into the fuel lines before the filter and into the filter itself. With all the junk in there, the fuel pump has to work MUCH harder and will usually die a few days after you run out of gas.

So if you have a very clean gas tank and you don’t try to restart the car, I suppose you’re right.

I support hellokit’s contention that a fuel pump can quite happily run for a while, no fuel, without self-destruction. It is a low wattage device that barely gets warm. Afuel pump can easily be engineered for successful operation even when run dry. But there is no point quibbling over yet another popular car myth. Don’t run out of gas; it is a nuisance to walk to the filling station.

The problem with your premise is this: if the engine won’t run because it’s out of gas, and the driver keeps trying to restart it, there’s going to be very little heat generated by the fuel pump since there’s no fuel to pressurize. The pump motor will be virtually freewheeling, and that doesn’t generate much heat.

As for “Also, when you do run out of gas, gunk gets into the fuel pickup …” where is this “gunk” residing before you run out of gas? The fuel is always picked up by the pump from the bottom of the tank. Running the fuel level down doesn’t change the place from which the pump draws. If there’s “gunk” at the bottom with no fuel, it’s at the bottom when the tank is full as well.

That’s true-- although I think it’s a matter of the lack of lubrication, not necessarilly the overheating.

I will admit that I don’t really understand the phenomenon, but I have observed many times that when an older fuel-injected car is run out of gas, the fuel pump almost invariably goes out in the next few days or weeks.

With regard to fuel pumps running dry without adverse effects- it is much worse to chronically run low on gas. Of course, the occasional event might not be catastrophic but the fact it continues to run does not mean it hasn’t been marginally damaged in some way that could not be determined without inspecting the internals.

The pump is designed to be submerged in fuel. What automotive part do you know that is OVERdesigned today? Circulating fuel without a reserve in the tank means the cooling effect is reduced. Starving a pump means the plastic gears do not get lubricated and will run faster than intended because they are not working against a load. I doubt this will convince anyone who believes there is no harm in doing this habitually.

However, a similar type of fuel pump is used on some aircraft. I like to read the failure reports and ran across a very detailed failure analysis of a crash that resulted from a fuel pump failure. Their analysis specifically pointed to evidence that the fuel pumps had been run low on fuel in the past and caused them to seize up. If an aircraft pump can fail from lack of fuel, don’t you think that a less robust design used in a car can have the same limitation?