Fuel gauge sending unit

[b5blue]

  26 years ago I replaced my fuel pickup/sending unit in my 70 Charger. Last week I replaced the tank and all related hardware. I took a peek inside the new sender and like all new senders it's not made proper for gauge calibration. (A straight strip with even spaced windings inside.) The old unit worked fairly well given my patched and dented tank so I opened it up to examine and here is the best shot I can get with my crappy camera. It shows how the hourglass shape and windings spacing convert fuel level into OHMS for the gauge.

[Nacho-RT74]

Yeap, new reproductions are made with straight strips, not triangular, hence why they are not accurated. The spaced windings TRY to emulate the ohms variation scale, but still is not accurate to the original specs. Even I would preffer they were better, I'm not greatly piccky with that, as far I can read full and empty stages. I can live with aproximate readings along the scale.

The shape of the diff tanks makes difference on the real reading too anyway, and the coil strip doesn't change between models as far I know. So maybe even you are getting 1/4 of tank, your sender will read maybe 1/3" and my sender will read 2/5, but on both we have 4.9 gals of gas ( I think 2nd and 3d gens get 19 gals tanks both )

[b5blue]

 With the new sender installed in the new bone dry tank my gauge needle read well below empty and 5 gallons added had it up to the empty line. 8 more gallons and I read less than 1/4 tank. I've ordered a "Meter Match" (  https://www.technoversions.com/MeterMatch.html  )  after searching and finding the guys on C body forum have been working on the same issue.  https://www.forcbodiesonly.com/mopar-forum/threads/fuel-sender-calibration-using-meter-match.55127/
  Why someone hasn't made the proper scaled winding strip yet is beyond me. It looks like it would fit many cars.

[b5blue]

  I'm making a ground strap as I don't trust the new snap on grounding connector that goes to a 50 year old fuel line. I've also noticed the sender's swing arm must contact through the winding housing to electrically provide that ground. (A potential fail or intermittent operation point.)  The old sender has a plastic float and it has a tea spoon or two of fuel inside. (The new one is brass.)   

[Nacho-RT74]

What I made is play with my sender not just bending the floater arm, but also with the points tab against the coil, trying to get the most accurate readings at full and empty. I got kinda satisfied with the results.

Factory sender was brass, later replacements went with plastic, now repros went back with brass althought I think not the same "thickness" of the original floater

[b5blue]

I installed the pickup in the tank while still in my living room. I checked operation and range looking through the filler tube hole before installing the tank. 

[A383Wing]

every reproduction fuel sender out there is total junk....get your OE sender rebuilt here

https://www.antiqueinstrument.com/

Bryan

[RollinThunder]

Hi b5 blue,
I wondering what the contact from the copper strip that contacts the resistor windings, looks like.   If this makes sense.  I took mine apart (original with the "triangular winding) too, and the strip that contacts the windings is a bent copper strip with a hole.  No contact button.  Don't know if that hole had some sort of "contact button".  Mine may have worn out, or fell out when I opened it, or if they are not supposed to have a contact.  If you could send a picture of the inside of the housing with the copper arm, the part that rides/contacts the windings, would be appreciated.  I should have taken a picture, sorry.

[b5blue]

I'll get ya pics.   

[Nacho-RT74]

The contact on the copper tab is similar to the flashers ones. Just smaller size

[b5blue]

Best I can do:

[RollinThunder]

b5blue,
Thank you for the pictures.  I can clearly see the tab.  My tab/contact is missing.  So that is good to know.  Much thanks    

[b5blue]

Your welcome, the "tab" is just a tiny spoon like shape pressed into the tip of the brass.

[Nacho-RT74]

as I mentioned, similar ( to not say IS THE SAME lol ) to points on dist point system... or the turning flasher points inside

[b5blue]

Yea mine has no tiny metal "pill" like a set of points has. 

[b5blue]

It takes a few reads and experimenting with the MeterMatch but I've got my gauge reading about correct with 13 gallons in tank. Next is to decide if I'm going to pump out fuel to fine tune calibration to E- 1/4- 3/4- F or just put some miles on it. 

[Canadian1968]

After realizing the problem with the new sending units in relation to the stock gauge. I have a Meter match on the way as well.

Have an empty tank , set at empty , go to gas station add 1/4 of your tank capacity, set,  add to 1/2 of tank and set,  Fill tank and set.

hoping its is as simple as it sounds !

[charger Downunder]

50 years later we still cant re-pro a fuel sender like NOS

[A383Wing]

50 years later we still cant re-pro a fuel sender like NOS

nope...that's why I recommended this place...he will rebuild your dead OE sender to like new condition and specs

https://www.antiqueinstrument.com/

[timmycharger]

Rather than start yet another post on fuel senders, I figured I would reply here.

All of a sudden I am leaking gas from the top of my tank. Went to jack it up to get under there and it just poured out the top by the sender.  I had a very small leak since installing the sender almost 7 years ago but now its very bad.

My gauge used to be sort of working, would give me at least a half tank reading but now its just showing 1/8 full all the time. 

I am thinking my leak was always the same, I may have just filled it more than I ever have before. I got gas a few times last week because I kept thinking I was low, the first time I got 5 gallons and the second time I have no idea because I had a guy chirping in my ear about my car and I was distracted.

I already purchased another sending unit and plan to replace it but what I am interested in is the Meter Match. B5 blue, you mention in one of the replies that you were going to pump out the fuel and calibrate it further. Does this involve taking out the sender again? Can you elaborate a bit on this procedure?

Where did you make your connection to the gauge?

Looking to solve this nonsense once and for all!

[b5blue]

Undo any line and fuel will siphon if lower than the tank or use a cheap fuel pump. I intercepted the fuel wire at the area by the kick panel. (At the connector.) 

[timmycharger]

Thank you, I completely forgot that it is in the kick panel.  I just ordered the Meter Match about an hr ago, looking forward to installing it.

Appreciate the help!

[b5blue]

  Keep us posted.

[timmycharger]

I installed the new sending unit, ring and gasket so hopefully that cures my fuel leak problem. The old sender was not working and had ohms readings all over the place, not sure why it failed but it did.

Before I installed the sender, the first thing I did was empty the tank by just unhooking my fuel line right before the carbs and attaching a hose that filled my empty fuel cans.  I then turned the key and let my electric pump do it's thing. I filled 3 (5) gallon jugs and then about 4 gallons of a 6 gallon jug so I am pretty confident that I was pretty much at the full 19 gallon limit.

I installed the meter match unit in the kick panel, unhooking the blue wire to the sender from the harness and used that as the signals.

I rigged up the sender by the kick panel so I could manipulate the float up and down and make my calibrations to the meter match unit.  Once I was happy with that, I installed the sender and poured the gas back in.

It took about 6 gallons for the needle to even move and eventually after putting all 19 gallons back in, it showed almost full. 

I am not quite happy with that so I will re calibrate it with the sender in the tank. Now that I know 19 gallons are in there, I will calibrate the meter match to show slight more full than that and then will drain it down till there is about 2 gallons in there and I will make that my empty.

[b5blue]

Sweet!

[timmycharger]

This evening I drained out and re filled the fuel again and re calibrated the meter match unit for both full and empty per directions.  Got it just about perfect and then I tested it by removing 6 gallons. It went from full to 3/4 full and then when I poured the 6 gallons back it went back to full.  Great so I thought as once I started the engine, it dropped to less than 3/4 and stayed there.  No clue why it changed but Im not messing with it for now, I just want to drive it.  I may give tanks.com a call.

[Dino]

1/4 tank just to fire it up? Sounds about right. 

The fuel gauge only has one wire running to the sender, with the sender grounded. Not much to go wrong there. When I calibrated mine, I had the fuel sender snd gauge on the bench. Much easier to adjust that way.

[timmycharger]

lol! yea I am very confident that both the meter match unit and sender are grounded properly, it is just strange that I had it calibrated perfectly with just the key on but when I started the engine, it is showing a different reading.

I also first calibrated it on the bench and after putting it in and filling the tank, I was not completely satisfied so I thought it would be better calibrating it in the tank.

I'm just tired of filling and emptying the tank over and over, time for some driving!

[70 sublime]

Wonder with the engine running you have a different voltage in the system to mess the readings up some ?

[timmycharger]

I believe that could be an issue, I did some digging this morning and found a thread on FBBO that links a video showing how to use the voltage correction feature on the meter match. 

https://www.forbbodiesonly.com/moparforum/threads/meter-match.256301/

[timmycharger]

I should have watched this video BEFORE installing the meter match.  It took longer to take off the kick panel and re install it than to turn on the voltage correction feature.  Pretty simply.  Key off, hold down up button on the unit while knob is at zero, at same time turn key to apply 12v and wait for LED to flash and done.

Result is rock solid needle showing full like it should when running.  Took it for a blast yesterday and beat the hell out of it to try to get the fuel to slosh around as much as possible and I confirmed that I also fixed my sending unit leak.

Fixed the leak by getting a new sender, lock ring, gasket and carefully hammering down the dabs with a wooden block to give a tighter seal with the ring. 

Having the lock ring tool helped too!

Oh and thanks to KD and John K on the tips on getting the pics big! Nice!