Fuel gauge issues?

What you're describing is typical when the movable contact on the float arm has a weak connection. The clue is the gauge usually reads correctly anytime the tank is between half and full, and the gauge acts up when the tank is between half and empty. Adding oil to the gas won't fix anything. At least once when you did that, you also filled the tank with gas. That put the float in the range where it's still working okay.

The fuel pump assembly has to be removed to do the fix. Once out of the tank, the float arm can be snapped off the housing. Look on the back side for the little metal arm / contact. Bend that out just a little so it always makes contact with the sensor, then snap the arm back on and reinstall the assembly.

Funny you should ask. It seems every time we schedule a job that we know involves removing the fuel pump, the vehicles show up with a full tank. The answer is "yes'. You know your approximate fuel mileage. As you use up the gas, note the gauge reading just before it drops to "empty", then calculate how much further you can drive so you use up as much as possible without risking running out. As I recall, water weighs around seven pounds per gallon, and gasoline is slightly lighter, so you can guesstimate how much weight you'll be lowering down. That is unless your car has an access hole in the trunk floor.

If you're going to test the results of your repair before completely assembling everything, keep in mind the pump motor will run for approximately one second every time you turn the ignition switch to "run". A lot of arcing takes place at the brushes in the motor, and that can cause gas fumes to explode. When the pump is assembled in the tank, there's no danger because those arcing brushes are either flooded in gas, or, when the level is way down, the air mixture is so extremely rich, it can't ignite.

The safest thing to do is fully install the pump housing back into the tank, then you can connect the wiring harness and turn the ignition switch on to test the gauge. If it's reading correctly now, reinstall the tank, then you can leave the ignition switch on when you slowly fill the tank. The gauge should not drop to "E" at any time as the tank is filled.

On a lot of cars, the gauge reading is "buffered", meaning some type of computer circuitry overlooks the sloshing in the tank, and it smooths out the reading. For that reason, it can take a while for the gauge reading to go up as you fill the tank.

Yes. Just a little below the tip of your arrow you can see the black sensor. It's just part of a variable resistor, similar to what was used on much older TV volume controls. The movable contact touches that sensing element, but it doesn't have enough springiness or tension to keep it in contact. I fixed a lot of these on older Caravans, but yours looks quite similar. You have to pop that arm off so you can bend the contact. It only takes an extra 1/16" or so to put enough pressure on it.

I'll be back tomorrow to see how you're doing.

Can't tell you the miles. I've never owned this model.

I don't see the float arm on the left one. If that is separate, look for the metal tab on the back side.

If both of these are for the same application, they are from different suppliers. There will be many more retailers for this assembly than there are manufacturers making them. The parts stores buy them from the same few suppliers. Regardless, they all have the potential to develop this problem. Bending the metal tab to make better contact is an easy task once the assembly is out of the tank. Replacing the entire pump assembly is an expensive alternative, and there's nothing saying the new one can't develop the same problem. My vote is to try to fix the old one first. It's a permanent solution to an intermittent fuel gauge.

Those don't have to be very strong. There's no forces acting on them other than the gas sloshing around. Most of this type of sensor is just a resistive paste that has been painted onto a small circuit board. Those boards are really tough, regardless what they look like. A lot of other sensors, like throttle position sensors, are built the same way.

Let me know how this turns out.

Not a bad gauge. A weak sensor. This is rather different from what I'm used to seeing. I see you have the arm snapped off already. On the Chryslers, the weak moving contact is on the back side of that arm, and takes just a few seconds to pull the contacts out a little.

Where are you measuring the resistance; is that between the two blue wires? On much older vehicles, I would guess the blue wire on the right goes to the resistor element for the gauge, and the left wire goes to a contact that turns on the "Low Fuel" warning light. They used to use two independent circuits. By around the mid '90s, they used just the gauge circuit, then, based on the signal voltage, a Body Computer, or something similar, turned the warning light on. If you follow those two wires into the connector, do they go to an orange wire and a yellow / black wire? If so, those are for the sensor element and the piece rotating over them has the contacts. That piece has to come off normally to give room to bend the contacts, otherwise you'll have to risk bending it without breaking it to allow room to stretch the contacts.

The only other thing I can guess is the copper-colored strips are the springs of the contacts and maybe there's a way to put more pressure on them. If that rotating arm can't be removed, is there way to push it in further so the contacts have more pressure on them?

More than likely a replacement fuel level sensor on eBay will be to replace the factory original one. That might not work on an aftermarket pump housing.

I don't see a common ground wire for the two curved strips on the sensor, so it looks to me like those two copper contacts are tied together. That would agree with the wiring diagram. Those copper strips provide the pressure to keep the contacts touching the curved carbon strips. Those are what need to be bent just a little so they provide more pressure. That would be easy to do if you could pop the assembly off its pivot peg, but often those are made to go on and never come off without breaking something.

The next thing to consider is to see if you can pull the end of the black piece away enough to give room to bend the copper strips down a little more. This is a place where you have to use caution because if you can't lift the black piece up, if you bend the copper strips next to where they're anchored, they'll bend the other way between the contacts and where you're pressing. That can actually reduce the pressure on the contacts and / or move them away from the carbon strips.

My next suggestions are a little radical, and I'd save them for a last resort when nothing else works. One is to pull the end of the black piece up enough to let the copper strips relax, then run a bead of solder on each strip. You'll need to shine them up first with very fine sandpaper so the solder will adhere. Once cooled and you let the black piece go back to its normal shape, the solder will try to hold the copper strips with more pressure on the contacts.

My last thought is to place a light coil spring over the copper strips, then use a piece of wire to hold it in place while putting pressure on the contacts. That would require some experimentation. For this type of project, I tear as many strands of wire as I need for the job from an old power cord. Those are easy to work with, and if necessary, you can solder to them. Heating them next to plastic will cause the plastic to melt and embed the wires, holding them in place. One word of warning here. If you use a soldering iron to melt plastic, set it to its lowest temperature, (if you have an adjustable iron), then clean the tip as soon as it cools. A lot of soldering tips today are iron-coated copper to make them last longer, but plastic residue eats that iron coating off, then the tip will burn away rather quickly. When I want to embed a wire in a plastic piece, I put a strip of copper over the wire, then heat that and let it transfer through the copper. That keeps the soldering iron tip clean.

If you don't mind the extra work, look for a similar model in a pick-your-own-parts salvage yard. See if you can pop the contacts off without breaking anything. If you can do that, bending the copper strips should be an easy solution. Often you'll find someone already removed the pump housing to get the pump, and they left the rest behind for you.