Petrol gauge remains at 1/1 until about half tank then descends normally

XK
1

It has been fine before, so this is new.
I searched the archives and found a few elaborate methods, but is there a simple explanation, and cure?

2

Two possibilities both relating to the sender unit in the tank:

  1. The float arm pivot has become sticky and remains in the full position until it gets bumped down to the real fuel level.
  2. There is a break in the rheostat winding and so you have an open circuit until the wiper gets to the other side of the break. Or the wiper is not making contact with the resistance winding at the top end. Comes to the same thing.
    The second possibility is more likely.
3

On my xk150, have similar issue. Tapping on the gauge makes it read correctly but it will stick on full. Pretty sure my gauge lubrication is the problem. I’m waiting for a bigger problem before tearing in to the gauge…

4

Get a proper hammer.