Continuing the Fuel Sending Unit discussion

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73Dart340Sport

73Dart340Sport

73dart340
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After following along on the earlier posts regarding the fuel sending unit, I decided to replace the one in my 73 Dart Sport. (I also ran out of gas on Saturday for about the 5th time which added incentive)

I have noticed that when the car is full of fuel, it will register about 1/4 full. Once below about 1/2 it does not register.

After testing the gauge with a tester to make sure it was Okay, I pulled the fuel sending unit. (I found that getting it out with the tank installed was space limited) After removing the unit, I tested it with my Multimeter. With the sender wiper in the full position I tested 10 Ohms. Empty it tested between 78 and 89 Ohms. Next I crawled under the car and attached the unit to it's lead and grounded it. With the ignition on, the unit registers full with the wiper arm up, and empty with the arm down. The gauge also followed the wiper in other estimated positions, confirming that it is working normally.

The plastic float has a small amount of trapped fuel, and the wiper moves fairly freely.

My next move will be to reinstall it in the car. However, before I do this (and fuel the thing) are there any suggestions regarding the life of the sending unit, and what else could have been preventing it from working normally in the past?

In other words, is it better to replace it, or keep it and continue to trouble shoot?
 
Change the float and you should be good to go. If there is fuel trapped in the one you have, it is leaking and needs to be replaced.
 
Thanx for the input!

I've tracked down the sending unit to Year One. I agree to the ground being the probable culprit. After having the tank boiled out next week I'll reassemble the thing and hope it works!
 
Hi all, new here. Just bought a 71 Dart Swinger for my son. Fuel gauge isnt working and was wondering if anyone could tell me a good starting point to try to fix this. I'm NOT mechanically inclined but willing to learn. Any good books with complete detailed instructions and illustrations I might wanna pick up? I want to begin slowly restoring it although its in daily driver condition. Thanks in advance :)

Joe
 
First check the sending unit in the tank like this post is talking about.
You would think this circuit is a bridge type, but I don’t think so.
The power goes thu the gage to the reostat (sending unit) and then to earth.
Your gage operates on a heated up piece of metal which moves the needle.
In my experience, most inop fuel gages are bad because something else failed first.
I’m not sure what it’s called but on the back of the instrument cluster there is a little relay looking plug in thingy. (We could call it a voltage limiter)
It functions sort of like the old school flasher. It allows a certain amount of current to flow. It heats up and opens the circuit to the fuel gage. Then it cools down and closes allowing more current to flow. In other words, it cycles power to the gage.
If it fails, the gage gets full 12volts uninterrupted and soon fails.
You can tell this is happening because the gage goes coo-coo (pegs) till it burns up and quits working.
There are other problems but this is what I have seen.
Other people may be able to help you more or correct anything my memory is wrong about on this. I assume 71 cars had this system like my later ones do.
 
most of the time on a mopar, the ground strap from the fueltank sending unit to the fuel line isnt working, or is missing. tray a jumperwire from a CLEAN BARE METAL spot on the frame to a clean bare spot on the fuel line at the tank. the gage should work. if not, unhook the sending unit wire at the tank and ground that. the gage should go to full quickly.
 
Thanks both of you :) My sona nd I will takle your suggestions this weekend. 1st things 1st and this is the 1st. Dont want him stranded, out of gas :)

And as soon a spossible i post up a few pics. I'll have my daughter take a few :)

Thanks again, Joe
 
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