HELP! Stumbled Died, Now it Won't Restart..

[andrewwynn]

Originally Posted by upallnight

If it's a myth how do you explain the OP finding a "lot of crud" at the bottom of the sump?



The pump is not submerged if the siphon pump is not working, that's why people can't start their truck even though the fuel gauge may indicate a 1/4 of a tank of gas remaining because there is no more gas at the bottom of the sump. Most mechanics will tell you that running an in tank pump without gasoline will eventually lead to early failure of the pump.



You can believe whatever you want to. I'm just posting what I believe and what the original poster posted. After all, I did post the solution to his problem, I didn't see you post any solution to his problem.

The pump will not be submerged during the last 15-20 minutes of driving at the end of its life. It won't be dry during normal operation down to 0.0 distance to empty. The x5 is designed to avoid ever having an exposed fuel pump.

Filling a tank before needed will not add one revolution of lifespan to a BMW x5s fuel pump. It's just going to mean 100s of more inconvenient stops for fuel that weren't needed with the added bonus of greatly increasing the odds of a surprise running out of gas with a ton of gas in the tank as that practice has a serious backlash of masking a soft-fail fuel pump.

Think of it like this: if you regularly check your tire pressure say weekly, you will discover there is a slow leak from a bad valve before any damage occurs.

If you on the other hand, added air to each tire and bleed off down to the proper amount , and did this weekly, only checking the pressure after adding air, you would never know that one tire was running 5 # low almost always causing internal tire damage eventually causing tire to prematurely fail.

On the x5. If you habitually prematurely add gas (don't periodically consume gas until the low fuel light comes on) you are avoiding a very important test of the cars health. You won't know that your fuel pump is healthy without periodically testing it and since it will eventually fail you will be stranded when it does.

If you, as I do bring the tank down not necessarily to the light but down to 50-60 miles distance to empty, I'm performing the fuel pump health test weekly but If you fill up too soon as my wife did, you are setting yourself up for failure because you will be nursing along a weak unhealthy "heart" at end of life and greatly reducing the chance of finding at a convenient time vs inconvenient time.

As for the "Crud at bottom of the tank". Unless the x5 was driven until it quit from fuel starvation, whatever the crud was has 0.0% to do with using the car with less than 1/4 tank and i would have to see the exact crud to even make a guess. It's more likely that crud entered via the filler neck than from the pump.

Once the tank is below half a tank, there is absolutely no difference from the pumps perspective until there is less than 2 gallons left. You shouldn't drive with less than 1/4 of THAT TANK (reserve tank) of fuel that is true. None of the 1950s myths of 1/4 tank of gas apply to the x5