The X5 left me stranded. Fuel Pump?

[oldskewel]

The fact that your friend towing it home fixed it may be a clue.

@AndewWynn has a great thread on here about the workings of the fuel tank. Basically it has two halves, with the electric fuel pump in the right half, and a siphon pump (passive) in the left half. The siphon pump sends fuel to the right tank, which is only needed once the fuel level drops below 1/3 (?).

If your siphon pump failed (common on these cars, although less predictable than the electric pump failure), it could be that your car died when the right tank ran empty. The description of not starting sounds exactly like a fuel issue.

Then when your friend towed you home (great friend, BTW ), it sloshed enough fuel from the left tank to the right that now you are OK again ... until that fuel runs out.

I know that sometimes with these old cars, the owner really does not know if the part is original. It could be that your electric fuel pump is not original, and should last until 300k miles. If true, replacing it might be worse than leaving it alone.

If you're tempted to keep driving it, and having a repeat of this is not a big problem, you could try filling up with gas and keeping it above half a tank. In that range, the siphon pump is not needed. If you do that for a while and things are rock solid reliable, it points to a siphon pump problem, which could then be confirmed by running the tank down to see if the problem reappears.

If you have the high cluster, you can do some measurements before then - one of the tests in there (#6 maybe) tells you the fuel level in left and right sides. If you don't have the high cluster, you can lift the rear seat cushion up and off (no tools, 15 seconds to do it) and measure the resistance directly on the floats on both left and right sides. Roughly it goes from about 50 to 450 Ohms as empty ==> full. Left tank has only the sensor. Right tank has 2 connections for the sensor and 2 for the pump, with them marked in the plastic cover. I forget what resistance the pump should be, but less than infinity would be good. Probably 10 Ohms or so.

If you do replace the pump, Pierburg (now owned by TI Automotive) is the OE supplier. That's what I got when mine failed at about 170k miles.

16-11-6-755-043 is the PN for just the pump. The plastic full assembly can be reused, which is what I did with no problems.

@AndrewWynn and others have good info here on repairing the siphon pump if you need that. It works on the Venturi effect, and when an o-ring fails and the created suction fails, no fuel is pumped. Very easy to open it up and repair it. I did that one pre-emptively one day when I had some time.