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MG MG Y Type - Fuel Gauge Follies...

I have just fitted a new sender unit - I have adjusted the arm and it works fine as can be seen by the pivot moving in the sender unit - however if I disconnect the wire from the tank sender unit completely the fuel gauge reads half full but if I connect it again it reads empty all the time....any ideas anyone?

Sorry folks ....just realised there is a discussion on this on the Hints & Tips page!

This reminded me of my recent escapade with my wife's classic Mini. The fuel gauge stopped working. I eventually diagnosed a faulty sender unit and ordered a new one.

I spent days spread over several weeks trying to get the new one to work. The thing worked perfectly if I operated the arm by hand, but as soon as I put it in the tank and added petrol, I could not get the gauge to read more than just under half full. I lost count of the number of times that I siphoned the fuel from the tank to remove and refit the sender, and then pour it back.

The car was built in 1992, one of the last to have a carburetter. Later ones had fuel injection. The cars with fuel injection had a slightly different fuel tank, with a different sender unit - a slight bend in the arm. Although the old and new senders looked slightly different, I assumed that it was just because they came from different sources. It was supplied based on the chassis number.

Our car had one of the later type tanks, as fitted to fuel injected cars, even though it has a carburetter. The slight bend in the arm is necessary to prevent the float fouling the inside of the tank as it rises, so it could never show more than about half full. A new sender of the later type solved the problem.

I am certain that the tank and sender unit are the original fittings because we bought the car at 4 years old with only 7000 miles on the clock. It seems that the gradual changeover from YA to YB in the 1950s was repeated by the successor company 40 years on.

M Long

Dave ,I have recently fitted a fuel sender and have found that the length of the connector to the float to be crucial .
NTG supplied the correct fuel sender and as always were extremely helpful .

Ed Winters
E Winters

I think I have the length Ok in that it moves up and down as it should and the pointer moves along the coil inside the sender unit- Paul Barrow has suggested some electrical resistance measurements I can make with a multimeter so will have another go to see if there is fault somewhere!


Ed is correct about the length. The same resistor part of the sender unit is common for MG Magnette and MGA but the arm is longer so depending on where you bought the arm, compare the length of it to the old one. If it is too long and will cause the float to hit the top of the tank too early and will give falsely higher readings throughout its range of travel.

However, going back to your original question I do not believe this is your problem as yousaid "if I disconnect the wire from the tank sender unit completely the fuel gauge reads half full but if I connect it again it reads empty all the time". This would seem to indicate maybe a grounding out somewhere possibly on the sender wire. How old is your loom?

Paul Barrow

This thread was discussed between 11/06/2012 and 13/06/2012

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