Fuel Sending Unit Issue

[Long Island RT]

I know this topic is beaten-to-death, but I still need some advice to determine what the hell I'm doing wrong.

Here's my story....
I have an a new Autometer fuel gauge:
http://www.autometer.com/cat_gaugedetail.aspx?gid=3550&sid=60
So it should have the right ohm readings.

I put 10 gallons of fuel in my car last fall to run the motor for the first time.  I had no reading on the fuel gauge at all.  So today I finally get a chance to pull the sending unit to test.  Before doing so - I grounded the blue wire going to the sending until and got a full tank reading on the gauge.
This means at least the the wires are hooked up correctly and my gauge works....right?

I also noticed that my new sender unit (I think I got from Rock Auto) doesn't have a ground wire, so i figure i run an alligator clip from the vent tube (or return tube) to a clean spot on the chassis - still no dice.

I remove the sending unit - Ground it to the chassis again - jump the blue wire to it while its sitting on floor.  As I move the float up - I don't get a fuel gauge reaction until its about 3/4 of the way up.  At that point its only reading like an 1/8 tank.  As I move it further - it shoots quickly to full...?

So I grab my multimeter and put the dial on Ohms - touch the 2 leads and adjust to 0.  I then put one lead on the stud that connects to the blue wire and touch the other lead to the base.  I get no resistance at all - 0 - no mater where the float is.  I am really a spazz when it comes to electricity so can somebody tell me how to do this right?

Thanks

[Dans 68]

It sounds like the resistance in the sender unit is not scaled properly, in that the resistance seems to come in all at once with a small float level change. As you have an ohmmeter it is pretty easy to check the relationship between the float arm and the output resistance. Connect the ohmmeter between the output stud (that the wire to the gauge connects to) and the body of the sending unit. The resistance at empty (float arm down) should be about 73 ohms, and at full about 10 ohms. If it is not close to these values then the sending unit is defective.

Post a pic on where you are measuring the resistance on the sender...it sound like you do have the right locations to measure the resistance, but obviously also have an short circuit.

Dan

[Hemidog]

Maybe these threads will help, if you haven't checked them already.

http://www.dodgecharger.com/forum/index.php/topic,57971.0.html
http://www.dodgecharger.com/forum/index.php/topic,57376.0.html
http://www.dodgecharger.com/forum/index.php/topic,57267.0.html

[FLG]

Hey man,

If ya need any help I think I gave ya my cell. Feel free to shoot me a text..ill prob be around this weekend if you need a second set of hands