Does anyone know anything about the location of the fuel pump inside the tank- specifically, how much fuel should be left in the tank to keep it cooled?Running on empty can be rough on the fuel pump, so I've often heard the rule of thumb to "fill up at a quarter tank". So let's say you're getting 40 MPG. That's 424 miles to E on a 10.6 gallon tank. Filling up at 1/4 reduces that to 318, which seems drastic.1/4 tank= 2.65 gallons, and Honda says the tank holds, what 1.7 gallons plus "a small reserve" after the light comes on (don't feel like looking it up right now). Let's say 1.8. That would be about 17% of a tank. At 40 MPG again, you'd be filling up after 351 miles, which seems more realistic.All that being said, my last fill up was 9.69 gallons at 390-something miles, at 40.67 MPG. By conincidence, right after the light came on, too- so the light didn't show up until there was only about a gallon left.I'm getting way to into the numbers because I'm bored and on lunch. So, anybody know anything about the pump?

 

Its usually not good to get below the fuel warning light because the fuel will flow back and forth on corners and uncover the fuel pump intake, thus running it dry. As long as the pump is pumping the flow of liquid will keep it cool.

 

Don't be paranoid and overthink things. It's not that fragile. Just pretend you never heard about that theory and drive on and fill up when you can, and at least when the light goes on.

If you run low enough where you are in danger of running out of fuel even changes in your velocity will cause the fuel to slop around. Or just going upslope versus downslope will. When you run out of fuel, your engine is gonna stop or start running rough and your car eventually cease operating. The pump being "cooled" is the least of your worries compared with your engine and ECU going nuts trying to compensate for no fuel spurts of bubbles in the fuel line.

 

^ Where in the world did you get weak fuel pressure? Has it not been hitting the gym? Anyway, this isn't a diag question, and never once did he mention a problem, symptom, and certainly nothing that would indicate **LOW** fuel pressure!

That aside, in terms of wearing out a fuel pump, YES, running less than 1/4 tank MAY cause exposure of the inlet on the pump, and YES, fuel cools the pump, so less fuel=less cooling. Long term, unless you're running out of fuel regularly, you likely won't wear it out any faster.
The OEMs are pretty savvy, and they know most idiots run their cars to empty (thus why there's a "reserve" built in- when the idiot light comes on, most people fill up. Some tanks have as much as 5 gallons at this point!), and they use pretty decent pumps that can cope with this.
The second biggest killer of fuel pumps (after running dry) is long road trips. Yep. Because many people stretch the piss out of their tank to save time, and extended running with low fuel for long stretches gets the pump good and hot. Then, each time you stop, you dump cold fuel (have you ever put your hand in a tank of fuel? It's COLD!) on that hot ass pump, and after a few fill-ups, you've put a nice hurting on your pump- Mark W.

 

An old husbands tale. Like most rules of thumb about car care, it is either outdated or was never really true to begin with.

 

Fuel pressure is regulated by a valve in the return line to maintain FI pressure. The fuel pump is capable of higher flow and pressure than the injectors need and the pressure is regulated by the valve in the return. Its often just a spring-loaded conical seat built in the fuel rail.
Fuel is recirculated by the fuel pump through the manifold and the excess is returned to the fuel tank pretty close to the inlet filter. It is possible to starve the fuel pump by insufficient gas around the inlet and thus the FI pressure can be insuffient, or weak even if the return valve closes entirely. Running the fuel level too low can and will starve the injectors, even damage them for lack of lubrication, the fuel, so if you run out of gas thats the reason for possibly having to replace the injectors.

 

Duke. sadib888 looks like a spammer. check out the sig.

OP. fill it when [or about when] the light goes on. you still have 1.6Gal of gas in the tank and that is more than enough to keep the pump covered. Gas tanks are designed to get gas to the pump so even with steeper grades, the tank will still guide fuel to the pump itself.

~SB

 

I'm a firm believer in not letting the fuel get too low because I had to replace a fuel pump on an older car after I accidentally ran it dry once. That pump had over 100K miles on it, and may have been run dry by previous owners of the car, but from my perspective running out of gas once = damaged fuel pump.

 

Empty tank is a concern, if my .5 tank level gets 200 miles I know I am conserving fuel with my driving habits, going for empty is more than just a possible fuel pump problem. Here in Florida it is a good idea not to run too close to empty due to major storms for half the year, we have seen them come up suddenly and then gas stations can be run dry, with people filling tanks, generators and reserves, besides no deliveries. Also most times when I do run close to empty that is the time I will see the tanker at the corner gas station with best prices. So even if 1/4 tank left means only 300 miles between fills it is still better than my last gas guzzler.

 

I'm with raytseng. Don't over-worry about it. If you habitually drain near empty, OK, probably not so good.

That said, I think all the reasons given above for filling up when not-that-close to empty makes sense. Our Fits have terribly small gas tanks, it's really annoying, but nothing's perfect ... and why not protect fuel pump life?

 

I normally try and keep my cars fuel tank at least 1/4 full to try and prevent as much water as I can from being in the tank due to condensation.
Why You Should Keep the Gas Tank Full | Driveline Auto - Quality Used Cars Sales and Purchase

The ethanol in the gasoline will supposedly absorb some of the water, which will then go into your engine.

When I started searching about fuel tank and condensation there are a ton of forums with everyone giving their opinion. I didn't see a real definitive answer from a reliable source. Where are the Mythbusters?

 

I stated this in another thread....I really don't worry about it. I'm too busy to be making sure I has up at a 1/4 tank. If I have to do some repairs at 150k whatever, even though I doubt it's a problem. I'd think if it was really that detrimental to the car the engineers would have done something about it. Now what I will do every now and then is maybe run some seafoam through the motor to clean out that carbon. The US does have some dirty gas....but once again I don't think running the thing until the light comes on is that bad for it.

 

Its quite simple really

todays cars have a certain reserve level. When that light comes on for low fuel, thats the lowest it should be ever.


As long as you never see that fuel light, you are perfectly fine.



Ethanol is BAD for cars. The shitty thing is, oil companies profits go up when they increase the percentage of ethanol in fuel.

Biggest reasons include 1)cheaper for them 2)you get shittier gas mileage and performance, leading to purchasing more gas


Its a giant scam. Dont forget throughout the years, even going into 3 or 4 decades ago, the Oil companies have queitly been purchasing rights to great fuel saving inventions and either shutting them down completely, or modifying them enough so teh impact isnt great enough tos tart a "new thing"

 

Horseshit.