New sending unit and fuel gauge is off

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Valveguy

Valveguy

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I had my mechanic install (the second) fuel tank sending unit and my gas gauge works as such: Reads full for about 30 miles and then drops rapitly to 1/4 tank after about 70 miles of highway driving. When I fill at the 1/4 tank reading, the car still has 12 gallons of gas. Has anyone ever expirienced this problem? My mechanic does not seem to know what the problem is. (74 duster, 225) Thanks!
 
Sure, you have the wrong sender that has the wrong Ohm rating. Swap it back out for the "Other" sender. As stupid as that sounds, the gauge manufactures make senders in 2 Ohm ratings. Take a look, closely, like through Summitracing.com.

http://www.summitracing.com/hr/

Check out the product line and when your searching sending units, click the box to compare and notice the ohm differences.
 
I just tried this and Summit only lists one sending unit for my car. (74 Plymouth Duster 225). I don't see where they list the ohm readings. Thanks, Tom
 
I had this problem with a 65 Stang, the cheap re-pop sending unit would show empty when it was still half full. I ended up getting an OEM unit for WAY more money and it worked perfectly. Can't say that this is your problem but thought I'd throw it out there.
 
I have the same problem, my old sending unit was leaking so i put a new one in and also upgraded it from 5/16 type to 3/8 type so i can run larger fuel line later on. Gauge worked fine before i did this after i did this the gauge only goes to 3/4 full when the tank is topped off and then it reads empty very quickly
 
If you never register 3/4 tank etc.. the problem is in the gauge.
Inside the gauge is a bimetal strip ( bimetal is 2 kinds of metal laminated together ), with a wire heater coiled on it that makes it warp to move the needle. Eventually that strip looses it original temper, or seperates or it just cracks. End result is a pointer either here or there. Hope that makes sense. I'd say buy another gauge, with your fingers crossed.
 
RedFish said:
If you never register 3/4 tank etc.. the problem is in the gauge.
Inside the gauge is a bimetal strip ( bimetal is 2 kinds of metal laminated together ), with a wire heater coiled on it that makes it warp to move the needle. Eventually that strip looses it original temper, or seperates or it just cracks. End result is a pointer either here or there. Hope that makes sense. I'd say buy another gauge, with your fingers crossed.
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I sent my gauges out to www.autoinstruments.com and hadall 5 of them rebuilt and the faces rescreened. It was 300 bucks but my speedo had a broke pointer so it should be less than that. A lot better option then buying a used one and hoping it works.
 
Some of those "restorers" replace the gauge guts with VDO gauge parts. Not that there's anything wrong with that. Long as it works , right ? :)
 
They have been working good for 3 years now. The days of guesing ow much gas I have and runing out of gas on the side of the road are over. That and wondering how fast I way going trying to use the vac gauge was a lot of fun. LOL Got me a tach to replace that worthless vac gauge.
 
TGKELLY2 said:
Where did you get it?
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I got it from www.chargerspecialties.com but I think other restoration supplyers have them too. It is just like the factory option tach that replaces the vac guage in the rallie dashes. So it puts it right in the middle where you can see it very well. I am very happy with mine and the install was easy. It bolts right in and you just need to run one wire to the coil and another to a 12 volt keyd sorce. I just ran mine on to a connector in the fuse box.
 
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