Faulty Fuel gauge reading

[Terry Riley]

Hello, my 1973 MGB roadster fuel gauge has started to give wrong readings. It works when the tank is full but when it gets to half or less it reads empty. I have dipped the tank and it isn't empty. How would i go about checking if it's the gauge or the sender? If it is the sender, does the tank have to be dropped to replace it? Thanks, Terry

[Bumpa]

As I often do, I will refer to Paul Hunt's amazing website mgb-stuff.org.uk. Have a careful read of this http://mgb-stuff.org.uk/gauges.htm#fuelgauge

You have three components to consider, the gauge, the sender in the tank and the voltage stabiliser. Paul describes how to test all three. You can remove the sender and float without dropping the tank. If you look at the RH (UK driver's side) of the tank you will see the sender half way up the tank under the rear of the car. It is held with a locking ring which you have to punch round anti-clockwise until it releases. If the tank is less than half full, by jacking up the RH wheel you make the fuel slop down to the LH side and the sender can then be removed without loss of fuel. You will need a new gasket and lock ring.

If it was me, the first thing I would check is the wire connecting the sender. It gets loads of muck flung at it and corrosion will cause faulty readings, but read Paul's article.

[Michael Barclay]

Hi Terry
I made up a little box a while ago to calibrate my fuel gauge. You are welcome to borrow it if it would help eliminate the gauge from the problem.
Mike Barclay