2

This does not always happen but it has happened twice in last 6 months. My fuel gage is accurate most of the times but these two times it was showing that there is 10-15% gas in my tank but my car stopped in the middle of the road and I had to call AAA with extra gas.

My question is that:

  • Is there a potential problem with my gas level sensor?
    • If so, why does it work most of the times BUT these two times?
  • May be something else is going on where there is actually 10-15% gas in my car but engine is not able to suck it properly?
  • Can it be a potentially big problem? I do not want to spend a lot of money if I do not have to

Any ideas?

  • What vehicle do you have, Make Model Year? Some vehicles are known to have fuel level sensor problems like GM. – vini_i Sep 29 '15 at 19:54
  • I have a BMW 325 i 2002 – Lost Sep 29 '15 at 20:30
3

The level sensor works with essentially sliding contacts. These contacts wear out over time and crud, dirt and corrosion can build up on them. Did i mention that the sensor is submerged in gasoline. Some cars have known problems with level sensors but i'm not aware of BMW specifically having a problem.

If you don't want to spend any money this problem can be let go. You can use your trip odometer to gauge how much fuel you have. For example my car gets at least 300 miles to one tank. If you get to 300 miles then fill up regardless of what the gauge says.

If the gauge goes completely bad it may trigger a check engine light because the car won't be able to run evaporative emissions tests.

  • Actualy, as I mentioned, earlier the problems has managed to happen only twice in past 6 months and also when it is a problem, the estimate is off by only 15-20%, which is livable conditions for me. What this is a potentially progressive problem or if there is any way to know if it can turn into one.. – Lost Sep 29 '15 at 21:06
  • 2
    @CoffeeBean There is no really good way to know. The gauge may be fine for another 6 moths or stop working tomorrow. But a word of caution, a mechanic won't be able to diagnose the problem if it's not acting up. – vini_i Sep 29 '15 at 21:11
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    Agreed. An intermittent problem (especially electrical) is nearly impossible to diagnose when it isn't acting up. You can end up spending a ton of money on diagnostics which gives you absolutely nothing. – Pᴀᴜʟsᴛᴇʀ2 Sep 29 '15 at 21:51
-2

It could be the sign of a failing fuel pump either. A failing pump couldn't deliver the sufficient ammount of fuel when the fuel tank low on fuel.

  • Why the down votes? The fuel pump have to work harder if the level of the fuel is lower in the fuel tank. So the pressure produced by the fuel pump is decreasing as the car consumes fuel. The pressure regulator before your injectors is responsible to release the extra pressure and maintain a constant pressure on the injector rail. But if your pump is not able to produce the needed fuel pressure (because it is old and failing) the car will experience symptoms of an almost and eventually empty fuel tank before it is actually running out of fuel. – gOldie_E36 Jan 29 '16 at 12:55

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