Gas gauge ... calibrate?

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Elessee

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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?
 
04_Sport_LS said:
Replacement. There is an issue with the float/level sensor in the tank. It is a mechanical device that cannot be re-calibrated.
Click to expand...
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.
 
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.
 
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.
 
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.
 
OldSchool1 said:
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.
...snip...
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 ... :)

Let us know how you proceed.
Click to expand...

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..
 
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.
 
Elessee said:
Wow! i couldn't ask for more. Thank you very much.
Click to expand...
You are welcome very much.

Elessee said:
"...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...
Click to expand...
That's why we should always ask before jumping into unknown waters.
Thank ~you~ for asking.

Elessee said:
I see these for sale at around $100. Looking at the photographs... Question: Where (or what) is the fuel level float?
Click to expand...
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.

Elessee said:
Does the strainer itself pivot, and it is the float?
Click to expand...
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.

Elessee said:
I don's see anything suspended, hanging off the side, like in a toilet tank.
Click to expand...
Yeah. Our Lincoln Mark VIIs are just a liiitle bit more advanced than a toilet tank. <I crack me up>
 
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
 
OldSchool1 said:
Elessee,
Nice picture.
It's actually from my car
Click to expand...

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
 
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.
 
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I didn't do anything yet because my dash has an electrical glitch. The tach doesn't work at all when the headlights are on. Play with the dimmer wheel, and the tach jumps up and down. Works fine with the headlights off.

I suspect the fuel gauge problem likely could be electrical, and related to this. The plan is to remove the headlight switch and see what might be wrong with it. Bad grounds or something, behind the dash.. Bad switch?
 
Elessee said:
...I suspect the fuel gauge problem likely could be electrical, and related to this. The plan is to remove the headlight switch and see what might be wrong with it. Bad grounds or something, behind the dash.. Bad switch?
Click to expand...

Seems like it would be more likely to be a problem with one of the connectors to the instrument cluster. It could be a bad ground connection. Maybe the cluster is grounding through the backlight bulbs, but it can't do that when power is switched on to the bulbs. Find and restore the missing ground, and the problem should go away.
 
I agree with Joegr but the very FIRST thing to do whenever ANY electrical issues pop up in our 1984 - 1989 Lincoln Mark VIIs is to replace replace replace the IGNITION SWITCH. In doing so, MANY electrical gremlins go away as so very much of our cars' power goes through this switch.

If replacing the Ignition Switch does NOT cure your electrical issue, then the next step would be to replace the Head Light Switch. When these switches get old, they raise resistance and cause the problem you mentioned above.

Stop back in and let us all know how you proceed.
 
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