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Old 10-30-2018, 10:22 PM
cn90 cn90 is offline
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semcoinc,

- The above tests are EXACTLY what I had in my 2006 X5 when fuel is below 32L. And that is normal as my siphon pump worked perfectly before I did the preventive maintenance.

- I just did the experiment the other day, the YELLOW warning light comes on when there is about 10L in the LEFT tank.

- As andrewwwynn pointed out in other threads, I am redrawing the fuel tanks so you can see. It is just descriptive drawing for the ideas (not to scale).

- First photo shows the real tank shapes. NOTE that the 5L well, where the fuel pump sits, is EXCLUDED from the level sensor calculation, so this 5L well is somewhat "sacred".

- The 2nd photo shows my understanding of the cross-section, as if you look directly from the FRONT of the car.

- Now you can see why when you turn R or L, accelerate or decelerate, the level sensor moves up and down, either by the swaying motion or the turns/braking etc. (without liquid moving it) or by liquid sloshing over the right side moving the R level sensor...

- The important lessons are:

1. The 5L pump well is "sacred".

2. Calculation is done via 2 level sensors and the sum is reported to the instrument cluster.

3. Fuel Level Sensor issue: sometimes the gauge shows 40% but the car dies from lack of gas. This happens either because:
a. The level sensor is stuck in the 40% position.
b. The resistor (the level sensor works by varying the resistor Ohm values) is kaput and reports an Ohm values consistent with "stuck at 40%", no matter where the mechanical float is...

4. If your car dies and you suspect failed siphon pump, try to jack the left side up (drive it up on a curb so the left side is up on the curb), this should slosh about 5-6L to the right side, allowing you to get to the nearby gas station. Or do a hard left turn lol...

Hope this helps...


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