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Author Topic: Fuel gauge sending unit  (Read 984 times)
b5blue
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« on: July 13, 2021, 10:08:46 AM »

  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.


* PICT0002 (3).JPG (243.36 KB, 1280x960 - viewed 394 times.)
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Nacho-RT74
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« Reply #1 on: July 13, 2021, 10:20:37 AM »

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 )
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Venezuelan RT 74 400 4bbl, 727, 8.75 3.23 open. Now stroked with 440 crank and 3.55 SG. Here is the History and how is actually: http://www.dodgecharger.com/forum/index.php/topic,7603.0/all.html
http://www.dodgecharger.com/forum/index.php/topic,25060.0.html
b5blue
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« Reply #2 on: July 13, 2021, 10:26:17 AM »

 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.
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b5blue
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« Reply #3 on: July 13, 2021, 10:42:48 AM »

  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.)   
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Nacho-RT74
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« Reply #4 on: July 13, 2021, 10:44:09 AM »

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
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Venezuelan RT 74 400 4bbl, 727, 8.75 3.23 open. Now stroked with 440 crank and 3.55 SG. Here is the History and how is actually: http://www.dodgecharger.com/forum/index.php/topic,7603.0/all.html
http://www.dodgecharger.com/forum/index.php/topic,25060.0.html
b5blue
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« Reply #5 on: July 13, 2021, 10:58:02 AM »

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.  2thumbs
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A383Wing
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« Reply #6 on: July 13, 2021, 04:17:40 PM »

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

https://www.antiqueinstrument.com/

Bryan
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RollinThunder
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« Reply #7 on: July 13, 2021, 06:41:12 PM »

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.
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b5blue
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« Reply #8 on: July 13, 2021, 08:14:05 PM »

I'll get ya pics.  2thumbs 
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Nacho-RT74
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« Reply #9 on: July 14, 2021, 12:51:26 AM »

The contact on the copper tab is similar to the flashers ones. Just smaller size
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Venezuelan RT 74 400 4bbl, 727, 8.75 3.23 open. Now stroked with 440 crank and 3.55 SG. Here is the History and how is actually: http://www.dodgecharger.com/forum/index.php/topic,7603.0/all.html
http://www.dodgecharger.com/forum/index.php/topic,25060.0.html
b5blue
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« Reply #10 on: July 14, 2021, 10:50:22 AM »

Best I can do:


* sendertab1.JPG (243.42 KB, 1280x960 - viewed 354 times.)

* sendertab2.JPG (246.34 KB, 1280x960 - viewed 351 times.)

* sendertab3.JPG (248.2 KB, 1280x960 - viewed 351 times.)
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RollinThunder
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« Reply #11 on: July 16, 2021, 06:32:59 PM »

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 cheers   
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b5blue
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« Reply #12 on: July 16, 2021, 06:58:00 PM »

Your welcome, the "tab" is just a tiny spoon like shape pressed into the tip of the brass.
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Nacho-RT74
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« Reply #13 on: July 18, 2021, 11:10:51 AM »

as I mentioned, similar ( to not say IS THE SAME lol ) to points on dist point system... or the turning flasher points inside
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Venezuelan RT 74 400 4bbl, 727, 8.75 3.23 open. Now stroked with 440 crank and 3.55 SG. Here is the History and how is actually: http://www.dodgecharger.com/forum/index.php/topic,7603.0/all.html
http://www.dodgecharger.com/forum/index.php/topic,25060.0.html
b5blue
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« Reply #14 on: July 18, 2021, 01:03:31 PM »

Yea mine has no tiny metal "pill" like a set of points has.  scratchchin
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b5blue
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« Reply #15 on: August 02, 2021, 05:20:08 PM »

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.  scratchchin
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Canadian1968
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« Reply #16 on: December 19, 2021, 08:34:30 AM »

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 !
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charger Downunder
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« Reply #17 on: December 24, 2021, 05:45:49 AM »

50 years later we still cant re-pro a fuel sender like NOS smilielol
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A383Wing
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« Reply #18 on: December 24, 2021, 04:18:35 PM »

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

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/
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