Gas gauge ... calibrate?

Lincoln Mark VII

  1. Elessee

    Elessee Well-Known LVC Member

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    Haven't driven this '88 LCS much in the last few months. Can't recall the last time I bought gas. I took a long drive today, several hundred miles. First thing was to gas-up, and seeing about 3/4 tank according to the gauge, I bought just a few gallons.

    To make a long story short, after a few hours, when the gauge read half-full, it felt like it was running out of gas. So, I put my 2 gallons of spare gas in the tank, and added 15 gallons ($60) at the nearest gas station. There was room for more...
    So it read half-full, but was empty.
    What's the simple procedure for re-calibrating this gauge?
     
  2. 04_Sport_LS

    04_Sport_LS Dedicated LVC Member

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    Replacement. There is an issue with the float/level sensor in the tank. It is a mechanical device that cannot be re-calibrated.
     
  3. Elessee

    Elessee Well-Known LVC Member

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    Thank you.
    Well, that's unfortunate. I see a photo. Autozone. Mark 7 fuel sending unit. There are fuel and electrical connections on this one. It looks easy enough to remove (possibly access it by cutting a hold in the floor of the trunk?). Bad news is ~$150. No obvious float device. Electro-mechanical or something.. may not be fixable.

    One weird thing is, i think the DTE (Distance to Empty) went up to like 520 miles when I added gas, but did not change as fuel was used up. I need to do some testing.
     
  4. 04_Sport_LS

    04_Sport_LS Dedicated LVC Member

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    I believe the part you looked up may be the fuel pump assembly. It would have a strainer sock on the bottom of it. The level sensor WOULD be more of a "float" looking device.
     
  5. Elessee

    Elessee Well-Known LVC Member

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    Yes, there's a motor, and it looks like a pump. Maybe the fuel level sensor function is integrated.
    Searching Amazon for "aftermarket car fuel level sensor", some have a pump, some are just little float things with a wire or two ($50).
    I carry the 88 shop manuals with me, but haven't found an independent fuel-level-sensor on this analog gauge LSC.
    No tools, no place to work. I may get new tires next week, and coordinate this job with that one.
     
  6. 04_Sport_LS

    04_Sport_LS Dedicated LVC Member

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  7. OldSchool1

    OldSchool1 Dedicated LVC Member

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    Being able to add 15 gallons to our 22 gallon tanks is a dead give away.

    The in tank fuel pump left the factory wit a strainer that has yet to be completely reproduced. From experience, when our fuel pumps die we save save save the original strainer/filter/sock and reuse it on the new pump. The sock of the new pump doesn't reach down far enough to empty the tank so it may APPEAR that we've run out of gas yet can refill 11 or so gallons and then the pump shuts off automatically.

    The only mechanical and moving part is on the pump itself and that's for the float. $150.00 for a pump that should last 20 years is actually reasonable.

    Dropping the tank is actually just as labor intensive as cutting through the trunk floor.

    The quick and easy fix is to fill your tank until the fuel pump kicks off automatically, reset your trip meter, then refill your tank every 150 miles no matter WHAT your 31 year old electronic fuel gauge :)

    Let us know how you proceed.
     
  8. Elessee

    Elessee Well-Known LVC Member

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    Thanks for the tip in the fuel pump strainer.

    I've already cut holes in this car, so one more won't detract from its value much. Since I'd be working outdoors with minimal tools, cutting the trunk floor may be easiest (after I pinpoint the position of the pump). This job sounds like fun, actually...

    I agree. Keep the tank topped up. The spout on my old spare gas can finally gave out. I don't like these new Federally Approved ones. I'm thinking of getting a water carrier instead. Come with a spout and vent. They are both made from the same material.. High Density Polyethylene..
     
  9. OldSchool1

    OldSchool1 Dedicated LVC Member

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  10. Elessee

    Elessee Well-Known LVC Member

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    Wow! i couldn't ask for more. Thank you very much.

    "...The clearance between the fuel connectors and the trunk floor is less than one-quarter inch." Just 1/4 " is a surprise. I mighta made a serious error here...

    I see these for sale at around $100. Looking at the photographs... Question: Where (or what) is the fuel level float? Does the strainer itself pivot, and it is the float? I don's see anything suspended, hanging off the side, like in a toilet tank.
     
  11. OldSchool1

    OldSchool1 Dedicated LVC Member

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    You are welcome very much.

    That's why we should always ask before jumping into unknown waters.
    Thank ~you~ for asking.

    The Fuel Sender for our Lincoln Mark VIIs is on the driver's side of the tank. I do not have any hands on experience with them.

    Yes it does and no it isn't.
    From the pictures that I've directed you to, these are our OEM sock filters/strainers. Always, always, always save and reuse them. As of this writing, no aftermarket fuel pump manufacturers are shipping their product with the OEM style strainer. The NEW strainer sucks air when the tank level get's below 1/4.

    Yeah. Our Lincoln Mark VIIs are just a liiitle bit more advanced than a toilet tank. <I crack me up>
     
  12. Elessee

    Elessee Well-Known LVC Member

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    Found a photo. Worth a thousand words. Now I see the float thing. I have high confidence I can fix it. Probably just rusted or jammed or stuck in position...
    Even if there's a faulty potentiometer inside that plastic control box, I could mess with it..
    Here's the thread. They talk about it.. I may escape with just an O-ring and some tubing clamps.
    THE LINCOLN MARK VII CLUB • View topic - fuel gauge sending unit
    mk7 fuel.jpg
     
  13. OldSchool1

    OldSchool1 Dedicated LVC Member

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  14. Elessee

    Elessee Well-Known LVC Member

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    Opps.. I didn't see that. Thanks for the heads-up. You sure do get around...

    Difficult to find a photo of the sending unit itself, but the tank is common. If this photo is of the '88 LSC the tank, I can probably extrapolate where the hole for the sending unit is, from the position of the other, pump hole. (maybe 18 inches to the East) Then cut the trunk. Good idea?
    It's probably mounted just like the pump is. Once the sending unit is in my hands, I'll know if I can fix it..

    tank.jpg
     
  15. OldSchool1

    OldSchool1 Dedicated LVC Member

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    You are correct.

    1985 - 1992 = four hole tank
    1984 only = three hole tank

    WP_20180312_13_58_29_Pro.jpg
     
  16. Elessee

    Elessee Well-Known LVC Member

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    There's the fill hole, the pump, a fuel gauge, and what's that little hole in the middle for? A return line?
    Raining, but I'll get started on this soon. I'll take photos and document my progress. Wish I had my hand-held sheet metal nibbler thing. Might need to order one..

    ------------
    Reading the Shop Manual,Volume D, page 24-50-2
    Fuel tank vapor valve assembly
    ...the fuel tank is vented to a carbon canister through a vapor valve assembly...... The valve is mounted in rubber grommet at a central location in the upper surface of the tank...
    So, the small center hole must be where the carbon canister hose enters the tank.
     
    Last edited: May 24, 2019

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