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Super Moderator
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Discussion Starter · #1 · (Edited)
Test your Fuel sender prior to dissambly.

Place your DVOM in to the pins on the sending unit, The Negative goes in to the ground pin (brown wire). The Positive goes in to the violet/black wire. OHM's Scale on the lowest setting.

As you move the float arm from the High point to the low you should see a sweep of OHM go from about 302ohms to 36 OHMS . With the arm raised as in a full tank you should see
36 Ohms, and with the arm at the lowest (empty tank) you should see 302 Ohms.

If it doesn't work verify the connectivity of the wires from the sender to the pins, that is you should have a wire that you can see with it apart that may need to be re-soldered, as the wires can get cracked and cold soldered to the PCB. NO OPEN FLAME Butane torch irons, use a old timey 27-30 watt corded closed Iron to solder or de-solder the wire. A solder sucker or solder wick to remove the old prior to soldering the wire with new.

Float arm at lowest point.

Float arm at highest point.

Repairing your Fuel Sending Unit

Repairing your Fuel Tank Sending unit.​
There are little Tabs that hold the cover plate that holds the Float arm to the rheostat.​
Carefully bend them back I use end nipper pliers.​
Carefully lift it off, don't drop that copper spring.​
Remove the Float arm and place that copper spring on something white.​
Clean the brush on the float with some 2000 grit and you can even bend it a wee bit to make better contact. You will bend it so that it touches the pcb on the sender as a flat tight fit.​
Here is the sending Rheostat, it is black with tarnish.​
Using Q-Tips, and Alcohol, Gently rub it to clean the corrosion. Once you have cleaned it inspect it for Cracks and Broken wires from the sender to the plug. If it is Cracked you will have to source a new one... If it is unsoldered then you will need to carefully re-solder it.​
(NO OPEN FLAME IRONS... Closed electric soldering irons.)
Once it is all clean I usually scrub it up and down in opposite direction to arm travel.​
Reassemble the float arm and spring Make sure that your float wiper is flat to the circuit board.​
Reposition the cover holding it all together, position it so it is tight and Crip the tabs back over tight….​
You can plug it pack on to the connector and test it by re-connecting the connector, then turn on the keys, BE WARNED THE PUMP WILL SPIT GAS WHEN KEY IS ENGAGED SO HAVE RAGS HANDY and NO SMOKING OR OPEN SPARKS/ FLAMES.
Moving the float arm from one stop to the other your Gauge should now be working more better.​
If you aren't happy with the FULL or EMPTY, you can bend those arms in or out that the float stops on.​
For reinstallation…..​
If your Gauge is still not registering totally full then the issue is usually in the instrument cluster, and that it i either the 10V stabilizer, Gauge, or connections. So first step is to clean the nuts holding the Gauge to the mylar.​
You can apply a 9V battery across the nuts to see if the gauge will deflect full.​
If it does then it is the connectors, or the 10V stabilizer.​
If it doesn't then it is the Gauge.​
To replace the Gauge see my How to fix a flaky water temp gauge to disassemble the Cluster.​

Super Moderator
10,660 Posts
Discussion Starter · #2 ·
Internals of the Fuel Gauge.
Fuel Gauge

Here is the Fuel Gauge out of the cluster.

It is similar to the Water Temp gauge as far as it is a nicachrome wire wrapped on a bimetallic spring.

Its construction is different.
To remove the Face plate you have to file off the rivets on the back.

But usually it doesn't go bad as far as a cold solder joint goes as the wire is
Wrapped over the studs then affixed with "hot" melt glue?".

It is interesting to not that the two arms that suspend the needle are adjustable for the needle deflection or Stop. You can adjust them for the needle movement to
Be above or below the desired stop, that is full or empty.

To test the Gauge you need 10 volts and a ground, a 9vdc battery will full scale deflect. But don't leave it on too long as the needles wire will turn in to a toaster oven. It uses millivolts of current…

The gauge works as this.
The needle is connected to both spring arms. Those arms are tied to the positive and negative posts.

The Needle is the "short" between the positive, and negative.
if you watch the movement under power you will see the wire heat up and cause the needle to pivot.

There isn't really much you can do to the gauge but solder the connections of the wires if they are broke.
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