2005 STS Fuel Pump going bad?
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  • 2 Post By ddalder
Cadillac STS Forum - 2005 through 2012 Discussion, 2005 STS Fuel Pump going bad? in Past Cadillac Vehicle Discussion; Hello All, Just a quick question for some preventative maintenance before I have a failure. I noticed when I fuel ...
  1. #1
    back-n-black is offline Cadillac Owners Member
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    2005 STS Fuel Pump going bad?

    Hello All,
    Just a quick question for some preventative maintenance before I have a failure. I noticed when I fuel my car that I hear a light thumping noise coming from the gas tank filler tube after removing the gas cap with the car running. Is my fuel pump on its' way out?
    The car was on empty when I noticed this symptom.
    Performance and fuel economy has not seemed to suffer. it has 93K miles on it and it has teh 4.6 V8.

    Thanks!

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  3. #2
    ddalder's Avatar
    ddalder is online now Cadillac Owners Connoisseur
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    Re: 2005 STS Fuel Pump going bad?

    I'm more suspicious that you may have heard the evap purge solenoid and it's nothing really to do with the fuel pump at all.
    back-n-black and back-n-black like this.

  4. #3
    Ludacrisvp's Avatar
    Ludacrisvp is offline Cadillac Owners Connoisseur
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    Re: 2005 STS Fuel Pump going bad?

    Additionally you really shouldn't be running the engine with the fuel cap off.

  5. #4
    curtc's Avatar
    curtc is offline OCD - Obsessive Cadillac Disorder
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    Quote Originally Posted by Ludacrisvp
    Additionally you really shouldn't be running the engine with the fuel cap off.
    Yep, don't do that
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  6. #5
    Aurora5000's Avatar
    Aurora5000 is offline Cadillac Owners Fanatic
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    Re: 2005 STS Fuel Pump going bad?

    I hear my fuel pump before I start my car and also sometimes up to a minute after startup. Mine works fine.

  7. #6
    sts4pilot's Avatar
    sts4pilot is offline Cadillac Owners Member
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    Re: 2005 STS Fuel Pump going bad?

    I think mine just went out. At first I'd notice a hesitation as I took a 90º turn with a good amount of force, than my car started showing the engine light and would shut down on me. I m checkin the pressure to see if my pump is bad. Hope it is so I can fix it but hope it isn't cuz the fuel pump is damn near 600 $

  8. #7
    sts4pilot's Avatar
    sts4pilot is offline Cadillac Owners Member
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    Re: 2005 STS Fuel Pump going bad?

    If you pump 87octane in the 4.6 v8 what in the car will mess up?? The whole system? Fuel pump filter and injectors?

  9. #8
    dkozloski's Avatar
    dkozloski is offline Cadillac Owners 10000+ Posts
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    Re: 2005 STS Fuel Pump going bad?

    RTFM! 87 octane is approved for the car.
    Don't mess with Binky Bear!


  10. #9
    Subsailor613's Avatar
    Subsailor613 is offline Cadillac Owners Fanatic
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    Post Re: 2005 STS Fuel Pump going bad?

    Maybe on the V6 , but NOT the Northstar V8.
    I wish....

  11. #10
    sts4pilot's Avatar
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    Re: 2005 STS Fuel Pump going bad?

    Chill homie the wifey pumped that shit not me. Also 87 isn't apporved for the 05 sts4 v8.

  12. #11
    EChas3's Avatar
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    Re: 2005 STS Fuel Pump going bad?

    The 2005 manual does say you may use 87 octane in the V8. Performance may suffer. Here's an exact excerpt:

    If the octane is less than 87, you may get a heavy knocking noise when you drive. If this occurs, use a gasoline rated at 87 octane or higher as soon as possible.
    In actual fact, it varies from car to car. Drivers are different and a whole host of other conditions such as temperature, humidity and altitude have a big affect. At higher altitude, less octane is required to prevent detonation (ping or knock). Vendors sell lower octane fuels in the Black Hills of South Dakota for that reason.

    High octane fuel isn't necessarily cleaner, better or contain more additives and it certainly doesn't contain more energy. It simply contains more anti-knock compounds. If you want better gas, use Top Tier fuel. If you can't, use well-maintained vendors that sell a higher volumn of gas so ithe fuel is less likely to have been sitting in storage tanks for a long time.

    Follow your manual. For the V8, that means try good regular. If your performance suffers, use mid-grade or premium. If you get a deal on a tank of 87 and it pings, top off soon with 5 gallons of 91 or better and that tank becomes mid-grade.

  13. #12
    atlrus is offline Cadillac Owners Fanatic
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    Re: 2005 STS Fuel Pump going bad?

    If you can't, use well-maintained vendors that sell a higher volumn of gas so ithe fuel is less likely to have been sitting in storage tanks for a long time.
    Couldn't agree with you more. Way too many people underestimate the harm done by old fuel. Which is exactly why you should never use mid-grade - there are just not enough people pumping it to keep it fresh. Also, most gas dealers do add better additives to the premium, compared to the regular, while some only add detergents and such to their premium. At the end of the day, the savings (reg vs premium) per 100 miles are so small - it's not even worth thinking about it.

  14. #13
    EChas3's Avatar
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    Re: 2005 STS Fuel Pump going bad?


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