My fuel gauge doesnt show the correct ammount of fuel

When I fill up my tank (premium fuel only) my gauge only shows 3/4 full....any suggestions on how to fix this?
-dvsog

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What car do you have... usually you have to change the sender unit on the tank to fix this problem. There was an instance where dirty fuel was sold and it messed up the fuel injection and fuel tank sender.
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I have a 99 ml320.

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Gotta change the fuel sender unit on the fuel tank.
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Did you mess around with your fuel pipe? These days people tried to save fuel by narrowing their fuel pipe, when the computer is not reading the proper pressure (i.e. marginal pressure), this will screw your fuel level.
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I havent touched anything.....I was going to "reset" the fuel sending unit, but when i looked at it there was 2 different connectors and i didnt know which was which.

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The fuel sending unit inside the tank is mechanical, basically a variable resistor, with a float on a lever. There is nothing to "reset". It is not reading pressure either.
Since the fuel in the tank flows in all directions when the car moves, the fuel gauge usually has a delay circuit to smooth out the fluctuation.
When the resistor surface goes bad (for example, due to residue), there is almost no fix other than replacing it. It may be cleaned but there is no guaranty. Comparing to the labor and time to take it out, replacing is a sure way. A sending unit may cost $100-$200. Some models have dual tanks, then they have two sending units and the same process repeats twice (doubling the cost).
I am not familiar with the ML body. Older model sedans (<90s) have top access behind rear seats. Newer models need to access from bottom which means draining, replacing, refilling. It is quite messy. Unless you are very sure how to handle gasoline safely, I would suggest leaving this job to professional.
Another choice is leaving it alone. I had a non-working sending unit in a Ford Taurus. I always refilled to full and used trip meter to guess when I needed to find gas station.
dvsog wrote:

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snipped-for-privacy@aol.com ha scritto:

ROTFL!!! :-D
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ha scritto:

Keep laughing, one day it will hit you in the head.
Don't assume all things are made the same.
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On Jul 3, 6:36�am, gregorymorrow at earthlink.net, writing as " snipped-for-privacy@aol.com" IMPOSTER wrote:

Dear Greg:
To Quote someone who said it so well.........
"Grow up. Stop using the lookalike fake nyms. Show some spine by posting under yer own banner, or stop wasting bandwidth (and everyone's time) with this sophomoric, chickenshit, cross-posting, pseudo-oppositional trash.
Apparently, no one of any recognizable gender wants anything to do with you. Hence this endless, weak-ass, ridiculous, basement- sockazoid game. Trust me, this is not the way to ameliorate that situation.
Repeat -- Grow up. Be cool. Talk sense.
And you'll have it made. "
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Dear Jerk:
Repeat -- Grow up. Be cool like me. Talk non-sense.
And you'll have it made in Hell "
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On Jul 4, 10:46�pm, gregorymorrow at earthlink.net, writing as a "JakTheHammer" IMPOSTER wrote:

Dear Greg:
To Quote someone who said it so well.........
"Grow up. Stop using the lookalike fake nyms. Show some spine by posting under yer own banner, or stop wasting bandwidth (and everyone's time) with this sophomoric, chickenshit, cross-posting, pseudo-oppositional trash.
Apparently, no one of any recognizable gender wants anything to do with you. Hence this endless, weak-ass, ridiculous, basement- sockazoid game. Trust me, this is not the way to ameliorate that situation.
Repeat -- Grow up. Be cool. Talk sense.
And you'll have it made. "
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In my 1982 300 TDT the sender has resistance wire looped around a shaft. When the tank is full, a float raises a contact up to the top of the shaft, so the electricity has to go through all the looped resistance wire. When the tank heads towards empty, near the bottom there are two contacts that come together. This turns on the "Low Fuel" light. As the float goes down with the fuel level, less and less of the resistance wire is in the circuit because the contact on the resistance wire slides down the shaft as the fuel level drops.
On my sender unit the resistance wire wore through, and the sender unit quit working at about 325,000 miles and 25 years on the car. That resistance wire is really hard to find, and the original stuff is in metric units, which is not the way wire like that is stocked here in the U.S. If you take an ohmmeter and a length of the wire, you can estimate the resistance per millimeter. That is the property of the wire that's important, and that is how it is sold.
The problem I ran into was that nobody seems to sell resistance wire retail in the U.S. anymore, even on line. They want you to buy it in 100 meter rolls, which costs more than at new sender. I finally hit upon a good guy at one of the wire places who just sent me 4 meters of wire that was pretty close to what the original was for free because his computer system was not set up to charge for less than 100 meters of wire.
I rewound the sender and put it in the tank and it works pretty good. I had to slightly compromise on the resistance per millimeter because the wire the guy sold was in Imperial units, so it was close, but not exactly the same. With the original, when full, the needle on the fuel gauge would go a little above the "full" mark on the gauge. With the rebuilt sensor, the needle goes exactly to the "full" mark when the tank is full.
The "Low Fuel" light, which does not depend on the resistance wire, works exactly like it did before.
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