It takes exactly 21 gallons to fill mine if I stop exactly when the light comes on. I have a 25 gallon tank.

 

Built 54 that comes out to 33 mpg. I don't think so.

 

what comes out to 33 mpg???

 

He misconstrued this sentence of yours...
"well i made it 50 miles with 1.5 gallons left"

I thought what you meant was:
The Light came on.
I drove 50 miles.
After filling up I calculated that there was 1.5 in the tank.

The way he read it was:
I had 1.5 gallons in the tank and drove 50 miles.

 

The first 10 times you try this, you will go between 52.5 - 61.3 miles. On the 11th time, you will go 17.4 miles before your fuel pump burns out leaving you stranded.

Oh, and between the 7th and 8th time, your truck will start to run poorly due to the fuel filter getting clogged up from all the sediment in the bottom of your tank.

Hope this helps!

 

Both urban legends. Have any of you ever seen inside the fuel tank??

The pump sits inside the sending unit which is a chamber that locks to the bottom of the tank and holds the pump, gauge sending unit, float arm, and a plastic reservoir with a pre-filter. Anytime the engine is running, the fuel pump is sitting in a puddle of the fuel returned from the fuel pressure regulator. If you do happen to run completely out of fuel, it's not going to do any significant damage to the pump.

The fuel filter isn't going to clog up because of it either. Anything that makes it past the pre-filter in the tank isn't going to hurt the pump, and anything that makes it past the fuel filter isn't going to hurt the engine. If there was enough fine dirt in the fuel to clog up the fuel filter in the first place, it's not sitting patiently at the bottom of the tank waiting to suddenly plug the filter. Eventually, through repeated fill-ups, the fuel filter was going to absorb those particles and plug up on its own. It's not the contamination in the last gallon of fuel that causes it, it's the contamination period.
__________________________________________________ ______________


To answer the original question, the industry standard is (and has been for years) that the low fuel light should come on when the tank level reaches 10% of the tank's capacity. In general, if you have a 25 gallon tank, the light will come on when there is approximately 2.5 gallons left in the tank. That doesn't mean the fuel pump is actually capable of sucking up all of that 2.5 gallons, but figure you've got a gallon and a half left. At 15 mpg, that means you're good for a solid 30 miles more or less. I've personally squeaked 60 out of it, but I'm sure I was on fumes.

Each vehicle will be slightly different... different vehicle attitude, slightly different resistances in the sending unit, traveling uphill versus downhill all makes a difference. No two vehicles will be perfectly identical, but figure on 10% as a rough approximation knowing you can't actually get all of it out.

-Joe

 

ic....

 

Oh really? I've personally known several people who have had clogged fuel filters after running their vehicles extremely low on fuel. Gas is light, sediment is heavy. Maybe you don't get sediment at the bottom of your tank, but other people are not so lucky. When there is not much fuel left you have a higher portion of sediment in the tank, and it normally would never get ingested into the fuel pump and passed onto the filter.

I've also been stranded with my buddy when his fuel-cooled fuel pump failed on his motor home. His mechanic informed him that running the tank low routinely was very hard on the pump, which was cooled by the fuel.


Cut and pasted from the web:

Why do fuel pumps fail? Fuel pumps can fail due to a number of reasons. This article specifically targets gear rotor EFI type fuel pumps which are the most common fuel pumps found in vehicles manufactured after 1985. The top reasons for fuel pump failure are contamination, overheating, and the gears in the the fuel pump wearing out over time.

Rust, debris, and dirt are three common particles that can somehow enter the gas tank and be fed towards or through the intank fuel filter and possibly into the fuel pump. These particles clog up your fuel pumps filter making it work harder to pump fuel. This causes stress and accelerated wear on the dozens of small components inside the fuel pump eventually leading to fuel pump failure. When filling up with gas, make sure no loose particles are being pushed by the gas pump into the gas tank or onto your gas tank cap. When installing a new fuel pump, clean out any partials from the bottom of your gas tank and ensure that dirt does not enter it while reinstalling the fuel sending unit.

Frequently running your vehicle on a low gas tank is extremely bad for your fuel pump and fuel system components. On many vehicles, approximately 10-15 times the amount of fuel your fuel pump sends towards your engine gets sent back to your fuel tank. This helps cool down your fuel components and the fuel in your gas tank. By running on a low gas tank, the fuel in the gas tank heats up a lot quicker causing the fuel pump to overheat or even worse, run dry. Avoid leaving your gas tank low whenever possible. This is very crucial during the first few weeks after a new fuel pump install. A new fuel pump should be installed into a a minimum of half a tank full of gas.

A typical gear rotor fuel pump is made up of approximately 200 components. After several years of use, these parts can eventually wear out causing the fuel pump to fail."

 

Not entirely true for the newer trucks...I can fill up with it running and watch it go up as the tank fills...I did not expect this to happen but I had to experiment with it. My 01 would not do this.

 

i can watch mine go up as im filling it if the ignition is on