Morris Minor Owners Club

So I had the petrol tank out cleaning it. Fuel sender stopped working once I re-fitted the tank. Then I fitted a secondary earth & it started to work again. Worked for a few days & now it has stopped again.

Any ideas? Sticking? fuel level was about half a tank before it stopped working for the second time but is currently reading empty.

More detail required.
1. Why were you cleaning the tank?
2. How did you clean it?
3. When it was reading half a tank how much petrol had you put in after cleaning .

What year is the car - the gauges and senders changed over time. Assuming a later 1098cc car with black speedo.
Also, have you done any other work that could affect the wiring?

Basic test: Remove the green/black wire from the sender and connect directly to a good earth. Turn on the ignition. Does the gauge read full? Disconnect the wire from earth, does the gauge read empty? If these tests are good then the problem is with the sender, if they do not work, then the problem is elsewhere, although the sender might still have an issue.

My initial thought are that you have simply disturbed the circuit somewhere.
You clearly didn't have a good earth so you've added a "secondary earth" which isn't required if there is the correct metal to metal contact of Sender casing to Tank to Body Shell.
Adding a 'Parallel Earth' isn't always the fix people think it is, it can just add to the problems.
Perhaps that secondary earth isn't a great contact either?
Perhaps the feed onto the Sender isn't a good contact?
It might be an old and tarnished surface on the connection, or it might be a broken crimp....
Simon has given you the basic checks to do, but just give everything a good looking at.
A Multimeter is always very useful if you know how to use one.

It will be a poor earth; you need to clean a few of the screw securing holes where the tank sits in the car body.