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MG MGB Technical - Fuel Gauge

My fuel gauge has stopped working, I've checked the sender, and it's got a live feed, which I rigged up to a spare, but still no reading. Before I remove the gauge, is there any thing else I should check, it's a 76 and there is just one wire to the sender.
c cummins

Earth out the sender wire at the tank - if the guage goes to full then it is a faulty sender or a bad earth between the sender body and the tank
Chris at Octarine Services

And if reads correctly (assuming you have petrol in the tank) when you earth the body of the sender instead of the spade it is a bad earth. The earth involves a series of mechanical joints, not ideal. The earlier sender didn't have the fuel delivery pipe as part of it and had a dedicated earth wire. However I was under the impression that the later system was for the 77 model year, if your sender doesn't have the fuel delivery pipe as part of it then the earth wire is missing or the spade has broken off.
Paul Hunt

Thanks Chris / Paul, I earthed out the sender wire against the delivery pipe on the sender and the gauge moved, so there's a good earth. I guess I will change the sender unit, which is preferably; I think; to changing the gauge.
The car is registered December 1976. I guess it came straight off the line to the showroom, and didn't hang around in one of BLs fields.
c cummins

Get yourself a new locking ring and seal - run the fuel level down and jack the car up so the sender is high - tap the ears of the ring round with a small chisel / old screwdriver - pull out the sender and take it to the bench - prise open the little locking tabs on the cover and inspect the winding wire where it connects to the post, they often break there - cleaning the shellac off the end of the wire and winding it round the post and twisting to secure it will often restore the sender function.
Chris at Octarine Services

"The car is registered December 1976."

FWIW probably 77 model then, these started manufacture in June 76.

My two originals, and the first two replacements, all had the winding broken in the middle so not worth trying to repair. The symptom with those was normal reading down to about a 1/3rd tank then it dropped all the way down as if the ignition were off until more fuel put in. If yours isn't reading even with a full tank then the wire could well have broken as Chris suggests. By jacking the right rear corner you can usually get the sender out without leakage with up to 1/3rd full.
Paul Hunt

This thread was discussed between 18/02/2014 and 20/02/2014

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