Came here to say I should have preemptively changed my fuel pump. '04 3.0i with 195K mi died tonight, on Christmas Eve, with three people in the car, at an intersection, in a snow storm, 20ºF outside. I kept telling myself "eh, it'll last" until it didn't and the pump went out literally at the worst possible time. Temps plunged today and I think the cold got it.

My advice after 15 years of BMW ownership: add it to regular maintenance around 150K mi.

Good judgement comes from experience and experience comes from bad judgment.

I’ve changed my in tank fuel pump about 4K miles ago at about 122k miles. Watch out for infant mortality of parts also, that can take you out of the fight just as easily.

Mike

It's time not miles. Do a little math. Mine was still going strong at 180,000 miles wife's died at 133,000.

With e10 polluted gas, the average life span is about 6000 hours: 180/6=30 mph, 133/6=22.167. Those were very close to the average mph of mine and wife's cars.

Let your trip computer spin for a month or three without resetting the average mph. Multiply that number by 6000 and get the estimated odometer lifespan.

If you're lucky enough to use non crappy gas, that will last 5000 hours vs. 6000.

Ive had one go bad in a bmw ever.


Wifes died at 250k miles. Wouldnt have died then if she wouldnt run it low on gas all the time.


The other bmw's never see less than 1/4 tank.


The 323i has over 400k on the original pump and still working great.


The rest of them all have the original pumps with over 200k on them except the 2013 which has 80somethingk on it.

200/6=33.333 mph average. If you drive a lot of highway miles it will not be hard to achieve 250-300,000 miles.

On an X5 the "more than 1/4 tank" has no bearing whatsoever on fuel pump wear and actually greatly increases your chance of getting stranded due to the more likely failure of the siphon jet.

The X5 fuel tank sump holds about 5.0L of fuel that's it. Any more spills over to the left side of the tank once you are below about 27L ( well above 1/4).

On other cars even BMW models that have a design to encourage gas to stay near the pump do not have the actual sump like x5 tanks just a skirt around the pump to keep gas from sloshing to the sides during turns.

Pumps no matter how well treated have brushes that slowly wear out and will last 5-6000 hours on average. (with e-10 gas; 4-5000 hours with e-0 unpolluted gas).

I'm not against picking up a replacement pump in the 150-180,000 mile range but it's one of the easiest repairs to perform I would wait for failure or at least until you get over 5000 hours estimated on the pump before replacing.

Unless wife actually ran the pump dry, the whole 1/4 tank thing is a myth from the 50s and 60s.

250/5=50 250/6=41.667. if wife's average speed is between 41 and 50, 250k miles is the expected life of a fuel pump.

At 400k, 400/6=66.667 means almost exclusively highway miles: a pump that age is going to be almost out of brushes and bordering on miraculous. (unless you run e85); apparently more ethanol adds lifespan.

You don't live in an alternate reality where you can treat a pump nicer and get the brushes to not wear. The pump is running 100% of the time that the engine is on it doesn't matter the speed etc.

That said just like the E10 will improve lifespan, you might be using gas with another additive that will add even more lifespan but it will not double the life. I'm sure there are outlier that will last 8000 or even 9000 hours as a fluke that's why I don't recommend preemptive replacement

On the low fuel part your thinking of the oh its got an 1/8th left or so.


Im talking nothing showing on the gauge most of the time. Even with the sump its going to run dry at times. Ive had to push the thing to the pump for her before because she ran it OUT of gas at the GAS station.


I cannot fathom why she thinks it takes more effort to keep it full and never let it get under a 1/4 vs praying you get to the gas station and having to schedule what time she leaves for work so she can get gas.


As for the 323i, yep it will run out of brushes eventually but since its more or less a toy now and isnt used anymore Im more interested in seeing how far it will go now :)


Need to sell it but its more trouble than its worth to try to sell it around here. Paints fading but otherwise its mint.

Also only had one failure over 15+ Bimmers. I agree with Andrew in that the replacement is so easy, unless planning an out of town trip, preemptive replacement is not necessary. Now, if over 150k and going out of town, might replace it to eliminate the worry.

So what was the reasoning behind this myth?


With my diesel Ford truck it has been said that letting the fuel supply get below 1/4 tank increases the chance of getting air into the fuel system that can damage the fuel injectors.


Outside of my diesel truck mentioned above the only reasoning I've heard for not letting the fuel get close to E is to prevent debris from the bottom of the tank getting sucked up. Not sure how much debris the average tank has in it but perhaps this was based on metal tanks rusting?

In the 50s and 60s the problem was dirt and lack of cooling would cause faster damage.

Modern cars have tank/pump design that will keep the pump foot submerged well below 1/4 tank, the X5 to extreme. The pump will be completely submerged until there is less than a gallon of gas left no matter the pitch or roll of the car.

You can drive up a 20° incline with the tank reading 0.0 miles to empty. (when tank reads empty there is still 3.6 liters of fuel).

It's worth looking into how each car fuel supply works. The X5 is a very special case that doesn't require any fuel before the low fuel light comes on.

It does have a design defect that requires looking into where an o-ring will fail in the siphon jet and will cause fuel starvation at about 1/3 to 1/4 tank of fuel.

That situation should be occasionally tested, I suggest at least 1-3x per year, drive down to 10 miles to empty or so to confirm the siphon jet is working.

Best to have the obc hidden menu six running. If the right tank drops to zero before the left tank does indicates the siphon jet is not working properly. If the right side (which should read about 1.4L for the last 1/3 ), ever drops to below one liter, immediately stop the test and get gas, then fix the o-ring on the siphon jet.

At 160-190,000 miles our trucks had less than 1/10g estimated dirt at the bottom of the tank. One I didn't bother to clean out one I siphoned dry so I could weigh and get exact amount of fuel the sump holds. (5.0L: 1.4L shows on the gauge, 3.6L reserve below the zero on the dash gauge).

The reasoning for keeping > 1/4 tank doesn't apply at all to the e53. I was stranded twice on the freeway due to my wife's never letting tank get below 1/4 which allows the blown siphon o-ring go undiagnosed until you need the last quarter tank and you can't use it anymore.