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Fuel Sending Unit

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money pit

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I'm tired of replacing the aftermarket sending units and trying the different grounding fixes. I tried everything and my fuel level is still way off. Does anyone know where I can get an NOS sending unit? I heard they are pricy but it may be worth it. Any thoughts? Thanks
 
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There's some info in this thread that may help. My rheostat is perfect through the whole sweep but the gauge is off by about 1/8 of a tank. That's just a matter of me getting around to bending the arm with the float on it.

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Sendin unit issue

My 73 Challenger new fuel sending unit measures 72 ohms full at9 ohms empty which Is accurate however at half full its at 54 ohms. My Rally fuel gauge shows empty at 1/2 full. Thoughts?
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moparleo said:
No guarantee they will be accurate either. There are videos on calibration, but the old float style will never be accurate like modern units are. Very old technology. Just a rheostat type.
Click to expand...
I don't think its a matter of calibration. I can fill the tank, it will read full for a few miles, drop to a 1/4, go back up to 3/4, go to zero. Its a similar situation I had with with the neutral safety switch. I went through 2 aftermarket switches and after reading a thread on this site, I switched to a NOS. Problem solved. I read a thread also on this and another site, where they had the same problem until they went to a NOS sending unit. Thanks.
 
EW1BH27 said:
There's some info in this thread that may help. My rheostat is perfect through the whole sweep but the gauge is off by about 1/8 of a tank. That's just a matter of me getting around to bending the arm with the float on it.

www.forebodiesonly.com

Sendin unit issue

My 73 Challenger new fuel sending unit measures 72 ohms full at9 ohms empty which Is accurate however at half full its at 54 ohms. My Rally fuel gauge shows empty at 1/2 full. Thoughts?
www.forebodiesonly.com www.forebodiesonly.com
Click to expand...
My fuel level is all over the place while I'm driving.
 
Not sure if this matters for your issue, but do you have the grounding strap that jumps the rubber fuel line at the tank installed?
 
Juan Veldez said:
Not sure if this matters for your issue, but do you have the grounding strap that jumps the rubber fuel line at the tank installed?
Click to expand...
I grounded the sending unit directly to the battery. I think I'm on my third sending unit.
 
I think the straps on the gas tank are part of the ground . i believe i sanded them down to make good contact. I know theres a stud for the ground wire but the straps are part of the ground
 
Check the float arm for side to side play as well. I had a pricey aftermarket unit that was supposed to be "premium" with so much play, it was grounding to the pick up and causing very erratic readings. Bending the arm out fixed it but in the end I went with a $30 3/8 pick up from Vans and it's been very reliable. In case you do want to go aftermarket, I run Speedhut gauges and the fuel gauge can be calibrated to the individual sender, not just the typical mopar range. I get accurate readings and the needle doesn't bounce around hardly at all.
 
moparleo said:
Remove the sending unit and test it before you start buying a bunch of parts. They are a very simple mechanism and it could just be a poor connection causing the wide fluctuations and might be repairable.
Click to expand...
I tested the sending unit outside of the tank. It worked well. Read empty, 1/4, 1/2, full when I actuated it. When I placed it in the tank, it read 1/4 with the tank full. I read a couple of threads on this site that had the same experience. Thanks
 
73Dodge said:
Check the float arm for side to side play as well. I had a pricey aftermarket unit that was supposed to be "premium" with so much play, it was grounding to the pick up and causing very erratic readings. Bending the arm out fixed it but in the end I went with a $30 3/8 pick up from Vans and it's been very reliable. In case you do want to go aftermarket, I run Speedhut gauges and the fuel gauge can be calibrated to the individual sender, not just the typical mopar range. I get accurate readings and the needle doesn't bounce around hardly at all.
Click to expand...
I currently have Autometer gauges. The autometer gauge is calibrated to the Mopar sending unit. I'll look into the the Speedhut gauges, Thanks.
 
My pleasure. Hey a silly thought but just throwing it out there, to verify the sender is clocked correctly in the tank. If it's in at an angle it can read as your describing. Typically there's tabs on the tank that line it up correctly as you insert it.
 
73Dodge said:
My pleasure. Hey a silly thought but just throwing it out there, to verify the sender is clocked correctly in the tank. If it's in at an angle it can read as your describing. Typically there's tabs on the tank that line it up correctly as you insert it.
Click to expand...
I had thought about that but the sending unit will only go in one way because of the tabs. Thanks
 
Had mine rebuilt by TriStarr inexpensive, quick turnaround and it works perfect

1DB2ACB1-BB2A-424E-8719-6E683E1708E6.jpeg
 
If it is jumping around, don't ignore the possibility that it is either the wire from the fuel gage to the sending unit that has deteriorated, or the 12V feed to the fuel gauge that has the same issue. Check those before you buy any more sending units.
 
ctaarman said:
If it is jumping around, don't ignore the possibility that it is either the wire from the fuel gage to the sending unit that has deteriorated, or the 12V feed to the fuel gauge that has the same issue. Check those before you buy any more sending units.
Click to expand...
I ran a new wire from the sending unit to an aftermarket gauge (Autometer) that operates on 12v. Thanks
 
Lots of folks are buying add-on controllers to calibrate their sending units. Much cheaper option than NOS.

Speedway sells one and others. FBBO has some threads on the subject.
 
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