As with most here, Ive fought this issue from day one almost. For a couple of years I just dealt with the inaccurate readings. Typically, on a full tank the gauge would read 1/2. When the needle moved to "E", I still had somewhere around a half tank. From there, it would be anyone's guess how much was really left.

Last year I found someone that had some older sending units made by the vendor to Chrysler. They're Mexican made with a date of 2003 if Im reading the stamping correct. Over this weekend I decided to drop it in and hope for the best..Big surprise that its still way off. Per my guesstimating, after the new unit went in, I put about 14-16 gallons of gas in. Sure enough, the needle went up to half. In one of the pictures it shows the needle a tad bit past the 1/2 mark, but ultimately it stayed right at 1/2, or just a tad below. Frustrated I left it alone yesterday and decided to spend another hour or so today on it.

On a whim I jacked the back end up as high as it would go and turned the key on. Surprisingly the needle went past the 1/2 mark to almost 3/4. Im glad to see that the gauge works, as I had originally thought maybe that was the issue.

I have the sender and the tank currently out of the car. I also have another 2 dash clusters with fuel gauges. How can I test these out of the car? Ive seen a few videos, but it doesn't explain what is hooked up where in order to test/calibrate the sender. Also...what is causing the difference in the reading when level compared to the rear jacked up on stands? Same amount of fuel in the tank. I initially thought the tab needed bent on the sending unit as it may have not let the float arm come up enough. Now I question that, as it reads higher with the rear up.

What gives??

Level ground:

Up on jack stands:

Take a read on this post I found and see if this helps you. Go down about 3/4 page and see if this helps you.

http://www.dodgecharger.com/forum/index.php/topic,57376.0.html

with the car jacked up the fuel in the tank is in a different (fuller) position. i went through this last spring with a 'Mexican' made sender. ended up like you did, saying 'good enough'.

i did do a complete step by step write up here as i went along. Randy at Dixie had asked me to test them for him to see if they were any better.

That's an interesting read in that thread. I hadn't seen that before. I had wondered about the float not being able to raise any higher in the tank. That doesn't really explain the difference though when it's up on stands.

I was able to get one close and this was a Vans A body sender,had the tank set up with a jumper wire next to the car and kept bending the float and checking the gauge.I just stuck a small dowel through the filler hole to move the float and check the gauge.About 2 gals left on E and it moves quick from 3/4 to 1/4 but at least it goes to full and empty

I suggest you try to find a NOS fuel tank sending unit. I'm talking one from the 60's or early 70's, not 2003, or Mexican junk. I had pretty much the same issues for years with my car. Then I decided to fix it right once & for all by finding a NOS sending unit. It took me several months but I did find one. They are still out there. As soon as I pop it in and hook everything back up I had a accurate working gas gauge. Best thing I ever done to my car. Nothing beats a good NOS part.

I agree, but I haven't been able to find a NOS 3/8" sender.

with 2 AA 1.5V penlight batteries connected in series the gauge should read half. I forget the connections, if I can find it I will edit/post but I would assume the terminal to the tank sender would go to negative. EDIT positive to I terminal and neg to S terminal & might even been a D cell. I did it once & got halfway but I don't remember what battery size I used

Ok. Thank you. I'll try that this evening.

Im assuming that the float was/is able to travel higher in the tank as it read higher when on stands. That would probably mean an adjustment to the actual insides are in order. Any ideas here?

Ground straps were used before and after everything, so I doubt the issue is a ground problem.

run an extra a long you are under there and if you can. the metal the straps are made of can deteriorate and effect the resistance.

it's pretty easy to modify a good 5/16" sender to 3/8" or 1/2". i have done that many times. just remove sender from pickup tube carefully, unsolder 5/16" pickup from mounting plate. "swedge" original pickup holw with tapered punch to a snug fit for your 3/8" or 1/2" tube you have bent up to match your original 5/16" tube. resolder new tube to retainer plate. the "swedge" created by the tapered punch gives the new tube added support and additional room for more solder to be applied insuring a leak free seal. re-attach your sending unit to the new tube. you are done ! it sounds a lot harder to do than it really is. and is much cheaper than a re-pop unit that may, or may not work correctly. just my experiences that have been successful.

I put an aftermarket sending unit in my Dart and it was way off. I ended up putting gas in the tank in 2 1/2 gallon increments and making note of the readings on the gauge. I have a cheat sheet so I know how much fuel is in the car.

What Moparx said, modify a good 5/16 unit or if the tank is out or a new one going in (always a good idea if any doubt on the old ones' intergrity) then soldering in a bung is an option (what I did)

Yeah, tank is out currently. It's a relatively new tank as well. Probably purchased in 2006 or 2007.

That's way beyond my skills right now. I have one of the senders apart on my bench. Ill probably make some "adjustments" and go from here.

Bending the float arm down will cause the float to rise higher in the tank. That should make the gauge read correctly. You will need to play with the amount of bend to get it right.

with more thought I think it was "D" cells and be patient as it'll take a minute or two for the needle to start moving (3V is way less than 12)

i just used a single AA battery to see if a fuel gauge would move. gauge in my car was working, then it stopped, i had 4.95V from the VR on my instrument panel so i assumed my gauge was bad. swapped it out for another. still no workey.

so, i used a single AA batter wired to the gauge (not installed in any instrument cluster or anything, just two posts) and it went to about 1/4, the battery measured about 1.5V so two AA in series seems ok too..

remember, there is a VR on the instrument cluster, so the most the gauge should ever see is ~5V.

Oh I totally forgot about that (the reduction)

I tore the other sender apart and dang near broke it. I'm sure it's out of commission now. My luck. Haha. I'll try testing it later tonight.

the "voltage reducer" gets a 12v hit, then the internals cut it out at a predetermined resistance "heat" factor, be it points opening [like the originals did [i think], or using transistors and diodes like the new "solid state" replacements use to make the "average" voltage seen by the gages around 5 volts. using 3, 1.5v flash light batteries together would give you a good idea how the gage worked, as that would total 4.5v. i have done this in the past, but i limited the connection to short durations only to make sure i didn't hurt the gage being tested. this is why you will see the connection to the gage "flash" using a test light and an original, good working vr. the vr is opening and closing internally, creating a 5v "average" power signal.