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I recently purchased a used 2005 subaru forester (non-turbo). I initially noticed that the fuel gauge seemed to be dropping a little faster than what I would have expected based on the Km's traveled.

A week after I'd brought the car home (it was parked in the driveway for the whole week) I went to start her up to head to the shops and I noticed it was slow to crank over. Moreover, I also noticed the trip odometer had reset itself and the low fuel light was on (even though the gauge was showing a half full tank). I figured this was a battery issue so I had the battery replaced the following day.

After another 2 days of being parked in the drive after I had changed the battery I decided to crank her over to check that it would start up fine. The car started fine, but once again the low fuel light came on, even though the fuel gauge showed half a tank remaining. For both these occasions the low fuel light would turn off after approx 30-60sec of the car running.

Fast-forward another half a week and today I was driving around again and the fuel gauge and trip odometer were behaving fine. After visiting my father, I hopped in the car to head home and once I started her up the fuel gauge was on empty (on the drive to my father's place the fuel gauge showed just under half a tank) and the low fuel light was on. This did not go away after 5-10 minutes of driving so I pulled into a petrol station and filled up. Now, I filled up till full, but all I had filled up was 30 litres (according to the user manual the fuel tank has a capacity of 60 litres). Clearly it occurred to me that something is not right. So I proceeded to purchase and replace the meter fuse (to be honest, I'm not even sure if this is related to the gauge, but I could not find any other fuse for the gauge/odometer/tacho so based on the name "meter fuse" I figured this may be it). The car has so far remained on full since filling it up (however the fuel gauge was slow to rise to full, and by slow I mean slower than what you would expect, in fact is hung around 4/6 full for a little while before continuing to go to full) and replacing the meter fuse.

As much as I hope that this meter fuse has solved my problem, I can't help but feel there is something else at play. Can anyone with any experience offer me some advice? I have done some research and it seems that inaccurate fuel gauges are often a result of a bad level sender unit, however, if I had a bad level sender unit why was I getting a low fuel light and yet the fuel gauge was still showing half a tank? I can't help but feel this is something else.

Thank you for any help in advance, I appreciate the help. Sorry for the long post as well, but I thought it would be best to be thorough in my explanation.

  • Have you tested the fuel pressure with the vehicle off, on and running ? And if so did the needle slowly loose pressure or fluctuate alot... I almost feel like saying Its the gauge on Instrument cluster – hello moto Aug 24 at 10:05
  • Its a bad level sensor. – Moab Aug 24 at 16:23
  • @hello moto do you mean just observe the fuel gauge? – Zeta-Squared Aug 25 at 0:40
  • @Moab I've found online that my car has a level sensor on either side of the tank. Which one would be the culprit? – Zeta-Squared Aug 25 at 0:41
  • Sorry I'm really not familiar with fuel sensors. Is this the sensor on the pump or the sensor on the other side of the tank (apparently my car has two sensors in the tank) – Zeta-Squared Aug 25 at 5:02
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I have never had any car with an "accurate" fuel gauge. Not going to go into any definition of "accurate"...

But, at best, I take the gauge as showing "at least half full" or "time to consider filling" if below half. The senders are buffered by the computer / gauge so what you see is slow to react.

This slow reaction is done because on older cars we used to sometimes get a full tank by turning right and empty when turning left... :) Sometimes, if you had a failed voltage regulator, you could get more fuel in the tank by revving the engine... :)

The low fuel light may just be being tested as part of the dash initialization and is always going to be slow. As always, some cars are better / worse than others, you have to "learn" and understand what your car tells you.

  • That sounds reasonable. Surely there is something faulty when the gauge suddenly drops to half full while stopped at a light and then it slowly rises to just under full again? I guess I'll learn the mileage I get on a full tank and use that as a guide, I was planning on getting a full service in a few months so if it's not too expensive I can have the sensor changed then. – Zeta-Squared Aug 25 at 23:07

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