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Mystery Noise in New Parked 2011 Subaru

First, sorry if this is covered elsewhere, but I have no idea what to search to find this topic.

Last night my husband went outside and was standing near our 2 month old 2011 Subaru Forester. We live in the country, so it is very quiet. He was standing behind the car and could hear a "running" sound. The night was cold and the car had not been driven for about 6 hours. The only way he can interpret it is to say "I'm not saying it is the fuel pump, but it sounds like it." He came into the house and got the keys and opened the door to see if he could see something on the dashboard that might give a clue, but there was nothing, and when locked the car up again the noise had stopped.

He called the dealership today. The mechanic he talked to was dismissive -- my husband even heard him turn to someone and say "I'm just going to play dumb on this one" and at one point he put down the phone without a word while my husband was explaining the issue. The mechanic asked my husband to start the car and see if it was okay. My husband said it was slightly sluggish starting.

This from one of the most respected (?) dealerships in the area.

Husband was told "call us if it happens again". We're hoping to find out more, and hoping the car doesn't catch fire in the meantime.

Any clues would be most gratefully received. Thanks.


  • grahampetersgrahampeters AustraliaPosts: 1,785
    edited December 2011

    I am not sure if this applies to Subaru, but some modern cars run a fuel system pressure check some hours after being switched off. This has something to do with environmental controls to ensure that the fuel system does not have a slow leak. If I understand it correctly, the fuel pump runs for a while and pressure consistency is checked. Under normal operations for modern fuel systems, a high pressure fuel pump delivers a very high volume of fuel to the engine; excess fuel is returned to the fuel tank through a return line. Pressure cannot be reliably checked when the engine is run, because fuel is obviously diverted for the engine; hence the delay in checking until engine is cool after use. There has been mention of delays between 2 to5 hours.

    This topic has popped up in reference to other vehicles.

    I would certainly take it in to a dealer to check the fuel system over and get clarification from Subaru if unsatisfied. I would also be dropping a note to the dealer principal mentioning the "brush off"


  • ajo77ajo77 Posts: 1
    Interestingly enough, the same thing happened to my Forester '12 this evening. My husband suggested the same as yours.

    I was glad to note Graham's reply to your post. Did you check with anybody else to confirm this? I am only curious because I don't want to take this down to the dealership which is about 40 minutes away unless I really have to.

    I think there was a 5 hour lapse between my trip's end and the mystery noise. Thank you for this post and thank you Graham!
  • bearcrkrdbearcrkrd Posts: 167
    edited December 2011
    Right you are. I just purchased a 2012 Forester last week, and haven't read through the entire owners manual yet. But, one of my previous new cars, either the last one - '08 Civic, or the one before that - '06 Sienna, mentioned that very thing in the owners manual. It mentioned "don't be alarmed by this sound", in case you think your car has a mind of it's own, and has woke up. :)
  • ateixeiraateixeira Posts: 72,587
    Nice find. My first guess was emissions.
  • We're so grateful to Graham and all the others for this input. Our minds are at ease, that seems to be answer to our question. And Graham, we will be mentioning our little service (?) problem to the management.

    Many thanks, all!
  • Graham had it right except the purpose of the self-check.

    He said it was a "fuel system pressure check… to ensure that the fuel system does not have a slow leak… … a high pressure fuel pump delivers a very high volume of fuel to the engine… Pressure cannot be reliably checked when the engine is run…"

    He was correct in that the sound is the fuel pump, it is doing a pressure test, and the test cannot be done when the engine is running.

    But the check is not testing for liquid gasoline leaking back into the tank through the fuel injection system. The "fuel evaporation leakage" check is testing whether gasoline fumes are leaking into the air from the fuel tank's evaporative emissions control system (vent, charcoal canister, etc.)
  • I have a 2012 Subaru Forester and noticed the same situation tonight. It was about 30 degrees F in the garage. It had been about 5 hours since the car had run. I first noticed the "humming" noise and traced it to under the rear end of the car. I noticed it for several minutes when I heard a "pshhhhhh" and the sound stopped. I'm glad to read that it is a normal feature of the car. Thank you everyone for commenting.
  • You can find information about this on page 9 of your owners manual. It is the fuel evaporation leakage checking system.
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