Ebay fuel sender

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pishta

I know I'm right....
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Too the new out of my old tank to move it on over to the new one and checked the resistance through the travel. It 10 at full and ~80 at empty. Just a heads up. Its the 3/8 model with return line provision. Seems pretty linear when I was watching it move with the float. F this thing stinks! 10 years of old gas.
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BTW the resistance to the float level should NOT be linear.
Exactly. That's why the aftermarket senders are never accurate. If your tank was a square box that aftermarket sender would be ok.

fuel sender Non-Linear Board.jpg


fuel sender Linear Board.jpg
 
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Yes, that's why I called out the linear measurements...buyer beware.
 
what size is the return?

i would like to find a 3/8 sender with a 5/16 return
 
Linear or not, I just need the dang thing to hit empty at empty and not half a tank. I finally found an OEM one for my Barracuda that worked but I still need one for my Polara.


Alan
 
Linear or not, I just need the dang thing to hit empty at empty and not half a tank. I finally found an OEM one for my Barracuda that worked but I still need one for my Polara.


Alan
Some people have had luck with the meter match. Might be worth a shot
 
Get one listed for a A-100 truck. They will fit right in and with the long arm be 10x more accurate than those short arm things. Won't be as good as the original but it won't be full forever, then drop to empty in 10 miles with lots of gas left in the tank. It will slowly go from full to empty and when on the E have about 5 gallons left. I have been too lazy to pull it out and try to bend the arm up a bit to see if I can get it to hit empty with just a few gallons in it.
 
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Jim, what year A-100 and thank you. I have the same problem with my 71 swinger unit.
 
There are many non-linearities:
resistance vs angle
angle vs height
tank width vs height

Presumably Mopar designers accounted for all when winding the fuel senders, but my guess is they made it much less sensitive near full. That seems typical for all cars, perhaps the purpose being that when the salesman says, "try if for the weekend", the gomer potential customer thinks, "great mileage, drove 300 miles and the needle still on 3/4". What really matters to me is how accurate "E" is. I don't care too much about "F" being perfect since I fill it until the pump clicks off.

In my Mopar dash clusters, I had to add parallel resistors across the dash gage input, plus adjust the gages a bit (have 2 factory screwdriver adjustments for zero and range, for experts only) so that the ebay Chinese sender read E and F right when bench-tested. Had to take one sender cover off and bend the wiper arm for more tension so it wasn't erratic. Also used an adjustable 5 VDC source so fuel and temp gages read about right (tested w/ resistors). Haven't tested in-car yet.

We still see idiots posting about their car mileage, using the tics on their dash gage. The only accurate way to measure mileage is the volume used from fill-up to fill-up which uses the calibrated fuel pump reading. Average multiple fill-ups to account for the pump not clicking off the same place. Don't trust your dash odometer until you calibrate it against highway mileage markers or GPS, and might need to calculate a windage factor to apply.
 
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Another reason the OEM sender isn't linear is the thermal gauge. Most common is a 20 ohm gauge. It has approx' 13 inches of nickle-chromium resistor wire that measures 1.5 ohms per inch at 68 degrees. As it heats up its per inch resistance changes. This is why half the 80-10 range and needle position is 23 ohms and not 45 ohms.
 
Another reason the OEM sender isn't linear is the thermal gauge. Most common is a 20 ohm gauge.
Good addition to my list. Also, the mechanical connection between the bimetal motion and needle motion inside the gage is likely very nonlinear. In modern cars, those signals go thru a digital processor. If there is a dash needle, it is just a motorized positioner, controlled by the processor. The designers could linearize it all in software, though not sure they do since I think they still purposely do the "fake good mileage at top end of needle" trick.
 
Im running the A100 sender. Its close but not perfect. Still better than the other crap ones on the market.
 
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