Question about 1999 Mercury Mystique

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When my fuel runs low, approximately 1/4 tank, my car acts as if it's out of gas and dies. I originally thought broken gauge; obvious, right? However, when I filled it up; it didn't take a full tank. Sometimes I'm able to put in 12 gallons; while other times it 'runs out' after only 9 gallons. Either way, it's a 15 gallon tank. I used to be able to get 400 miles out of a fill-up, easy. Now, I find myself filling-up every 240; to avoid being stranded. I've checked for bulges in the tank, none I can see. I've replaced the fuel filter several times; no change. I assume any fuel pump problems would be more persistant. And becoming more prevailent after a year and a half. I've got a code reader, and the only codes it shows are the ones that were present when I bought the car; and it ran fine. Perhaps, my tank is partially filled with dark matter. Does anyone have any ideas? And please don't suggest that I take it in for diagnostics. I'm not about to pay $70 - $100, just to pull it in their garage. Thank you!

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  • Alexander Thompson Dec 30, 2010

    Well, that cracked pick up line would surly fit the bill.
    Just like sucking through a straw with a hole in it.
    Looks like I'm going in!


  • Anthony Bloemer
    Anthony Bloemer Feb 04, 2013

    there is no pick up line on that model.. strainer attatches to bottom of pump.. and dir connection from fuel pump to output..



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Funny that you mention ' Dark Matter ' -- there is a possibility that you might have water contamination in the tank (?), you can try and get some gas additives that remove water from the fuel. also, there is the possibility that fuel pick up line has been damaged and is not getting fuel from as low in the tank as it use to.


Posted on Dec 30, 2010

Testimonial: "Thoughtful answer, outlining mulitiple possibilities. Followed up on additional comments. "

  • Alexander Thompson Dec 30, 2010

    I've tried pretty much every additive... As that is one thing I considered. I don't know how it could have accumulated that much water.
    As to the fuel pick up line: If I recall correctly, the pump I replaced on another Mystique had it's pick up integral(metal). If so, is that still a possibility?
    I suppose, the bumpy roads do a number to shake things ajar.

  • chris wheeler
    chris wheeler Dec 30, 2010

    it just sounds to me that there is something wrong with either the pick up line or the fuel itself ( cracks/broken/to short of a pick up = sucking air at a certain level ) or ( contaminated tank ).


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Its the fuel pump my car did the same for 2 year i started going by the mileage about a year ago and it just got worse soon it wouldnt even start i changed the fuel pump and now she runs perfect i got a full tank out of her and nothing i saw my fuel light for the first time in 2 years lol. try changing the fuel pump

Posted on Aug 16, 2012

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Its a bad sending unit so gas guage doesnt read right. i have a mystique that does same thing anytime anytime under quarter tank. fill it up and go by your milage instead of gas guage

Posted on Dec 30, 2010

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  • Alexander Thompson Dec 30, 2010

    That's what I first thought. But that doesn't explain then, why if it won't take the full 15 gallons. As far as I can tell, by comparing the milage to the gauge; it's working.
    Sometimes I can get 300 miles without running out - but then, sometimes I run out at 240 miles. It changes, from time to time. A 15 gal tank, at 25 mpg(conservative) should get 375 miles before running out. And I do make sure to fill the tank.

  • christopher hogue Dec 31, 2010

    its a short circuit in the sending unit, i have same problem, sending units a a small chip board that registers where the position of the float and has many electrical contacts it touches as it floats up and down, so if theres a problem with that if won't read right. ive replaced hundreds of sending units

  • Robert Charpentier
    Robert Charpentier Mar 30, 2011

    Its either that or you have a fuel pump that quits when it wants too have you tried a new pump?


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