Quote:
Originally Posted by cn90
- As long as you don't ever run fuel below 1/8 or have a bad siphon pump (in that case, keep fuel above 1/4), the typical Pierburg fuel pump goes to 180K-200K miles.
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Fuel delivery problem below 1/4 tank has to do with the MAIN pump failing not the siphon jet. *
Not sure where the "below 1/8" comes into play but sounds like a conceptual error. The E53 fuel tank only has 5L of fuel in the surge tank that is closer to 1/20th of a tank than 1/8th.
The x5 fuel tank works by flooding the surge tank to overflow any amount over 5L back to the left side of the tank and uses the siphon jet to constantly pull fuel from the left to the right.
Any time there is more than 5L of gas the pump will be fully submerged there is no difference once you get below 30L or so remaining since the right side of the tank holds no fuel other than the surge tank once below about 30L total.
A fuel pump will last about 5000 hours with pure gas and about 6000 hours with shitty gas (polluted with ethanol). Divide your odometer by your avg speed to get an hour of use estimate. If it's above 5000 time to consider getting a replacement. In fact, I just replaced my wife's and doing the math on mine it's getting close 4500 hours.
I would buy a replacement to have on have but the warranty would start when I bought it but when I install it so I'll just wait until it falls it's one of the easiest repairs to do.
* The seal on the siphon jet can fail but it will still work with a fully operational electric pump. If your right side tank does not report over 1L when left fuel is below 25L then you likely have a weak fuel pump or a leaky siphon jet.
You should at least annually drive down to single digits DTE to confirm your siphon pump is working. When electric pump starts to fail the first symptom will be running out of gas with gas still in the tank.