What mileage is on this truck? I'd be willing to bet that was more of a factor than cooling on the pump. I drive from full to to dead empty on every tank and every vehicle I've owned. Only 1 pump failure on an e30 @ ~135,000 miles. I think the pump being submerged to prolong life is an old wives tale. But as always ymmv and do whatever gives the best feels. But, I have never run a pump completely dry... So maybe doing that can accelerate its demise.

Au Contraire mon ami

https://www.quora.com/Does-running-c...car-out-of-gas

More info on running the tank dry and its effect on a fuel pump.

https://community.cartalk.com/t/runn...uel-pump/39621

And last but not least this is what Consumer Report has to say on the subject of running the tank to almost empty.

https://www.consumerreports.org/cro/...stly/index.htm

Second line in that article:

"Fuel pumps are either cooled by the gas around them or by the gas that is flowing through them."

It goes on to elaborate that running the pump dry is the major offense, not running the tank low.

Even CR, which I don't hold a lot of weight to when it comes to autos says, "The gasoline acts like a coolant for the electric fuel-pump motor, so when you run very low, this allows the pump to suck in air, which creates heat and can cause the fuel pump to wear prematurely and potentially fail."

This also says that dry running is what could kill the pump.

I'm not trying to convince anyone to do one thing or the other. Just stating my opinion that running from full to empty is probably not what killed a pump. Mileage/age is. If we were seeing pumps fail at 50,000 miles... I'd be inclined to possibly look into it further. But the only pumps I've seen fail have been well over 100,000 miles. Unless referring to the HPFP found in the certain variants of the e90/92 where there was a known early failure problem with them when they switched to direct injection. :dunno:

Don, we've been down the rabbit hole before: once the X5 gets to about 1/3 of a tank there will be 5.0L of gas around the pump no more no less so there is no difference whatsoever in how much cooling is supplied from being submerged until your distance to empty gets below 10 miles. Even during the last ten miles the fuel pump will remain fully submerged in fuel to keep it cool as there is almost a gallon of fuel that doesn't register on the gauge.

So: any of the old school thought process of keep a quarter tank etc having anything to do with the longevity of a fuel pump on the X5 simply does not apply it's perfectly safe to run down to the low fuel light every time.

At some point the siphon jet seal will fail and leave you stranded but a couple gallons of gas will get you home for a repair and then eventually the electric pump will fail and you'll need a tow. I have roadside assistance that costs me like $36/year for BOTH X5 and it paid for 5 years on the first time it was used.

The X5's fuel tank is effectively 5.0L once you are below about 1/3 of a tank so you would literally have to keep HALF a tank of gas at all times to increase the depth of the fuel above the pump. When below 1/3 of a tank there is no difference whatsoever in how deeply submerged the pump is from about 120 miles DTE to about 10 miles DTE the depth will be exactly the same as the pump well is overflowing to the left side of the tank continuously.

The biggest difference to pump longevity is alcohol. If you use shitty gas with 10% ethanol it will add 25% to the lifespan of your pump as Its life expectancy will go from 4000 to 5000 hours. (if you use 20% ethanol it goes to 6000). It will of course cost you a lot lot lot more $ in the shitty mpg and wear and tear on other parts but if you are forced to use shit gas at least there is one silver lining: longer lifespan of the pump

Follow up: it is bad to run a pump dry which on x5 can not happen until you drive about 15-20 miles AFTER DTE reads 0.0, unless your siphon jet has failed. There is no benefit at all for the X5 to have more than 1.4L of gas on the gauge at that point is were any additional fuel spills over from the pump side to the siphon side and provides no additional cooling due to being submerged. So for the X5, it is definitely an "old husband's tale" there is a benefit of having more than a couple gallons of gas in the tank. This only applies to the X5: I can't confirm any other cars that use this system, I've parked on a sloped driveway with 1/4 tank of gas and wasn't able to start my 2002 Ford explorer, most cars have a flat bottom tank with the pump which is not submerged for much of the time.

The X5 tank was designed to keep the pump submerged when going up and down steep terrain but has the side effect of keeping the pump completely submerged down to 0.0 miles to empty and from sucking air for another 10-15 miles past empty.

The X5 thinks it has A 5.0L gas tank: it is continuously refilled so it never drops but once there is less than about 1/3 of a tank the right side will show about 1.4L of gas down to about 7 miles to empty and only once you get closer than that to empty will the fuel pump start to have less fuel above it. You have to get below zero before the pump starts to become uncovered and to about negative 15 DTE before you risk actually running the pump dry.

Great experience for me; I cannot imagine a better learning situation than witnessing rational people in a rational discussion.


Me and fuel pumps...oh man. My 98 K1500 had 6 pumps before 200K miles; dealerships were happy when the warranty expired. Some told me the loud pump motor was normal, some said it was caused by a bad ground, and some told me the failures was do to heat; to keep a half tank.


The Bosch I have in the Chevy now has 100K+. That fuel pump R&R is a major PITA!



I live in a remote area and consider the vehicle gas tanks as generator fuel storrage; when the power fails for 7 days or more, that gas runs my freezer lol. So, keeping full tanks is important to us.


I don't think I'll run this pump below 1/4 until a level of trust sets in. Wife's uncertainty avoidance index is higher than mine, she refills at 1/2.

I'm parting a 2003 4.4i, i can get you a pump out of my car. PM me.

And you hit the nail on head: it's about personal feeling but here is the problem with the always fill before 1/4: you are settung up a false sense of security.

Exclusively due to my wife always find at a quarter tank I got stranded with slightly less than 1/4 tank because her practice was making a leak in the siphon jet pump.

The only real advantage of keeping more fuel in the tank is you can drive farther from home before having to stop, however dropping your range from 400-500 to 200-250 is not really a convenience in the long run.

Using test six you can confirm the siphon jet is working at least once a year or so.