XK 140 fuel guage wiring and testing

(David Mustarde) #1

Guage registers empty permanently. Low fuel light does not come on.
Found some petrol in float. Think I’ve wrongly wired guage. 3 green one side, GB other and GY to centre??? A 3rd Black wire exits the sender.

(Rob Reilly) #2


There should not be petrol in the float. Better check for a bad solder joint. You may be able to just drag a soldering iron over it to fix it.
People often have 19 and 24 reversed on the sender.
The black wire on the sender must be a ground.

(David Mustarde) #3

Thanks tons for the info which has enabled me to determine that fault lies with guage so need to srnd off once I can find the £100 to service it.


(Rob Reilly) #4

Its been a long time since I did this, so lets hope I remember it right.

On the back of the fuel gauge are two nuts. These control the position of two side coil magnets with respect to the center armature. It may be that you can fix the gauge by adjusting these two nuts so the coils are in close proximity to the center part without dragging on it. Move the float through its travel to see the needle move between empty and full.

I clamped the sender to the steering wheel and rigged up long jumper wires back to the tank, then put the center panel down so I could see the back of the gauge, and sat in the passenger seat moving the sender around while adjusting the two nuts. It worked and has been working ever since.

(David Mustarde) #5

Tks but the guage doesn’t work when I earth “T” terminal, I wish I’d started there cos I’ve created further probs but many thanks for your help.


(Eric Capron) #6


The gauge should read Empty if you ground the T terminal. If you leave it open (disconnected) the needle should flick to past Full. Also, make sure that the case of the gauge is correctly grounded as this is part of the circuit and that you have 12 volts at the B terminal with the ignition switched on.

If these last two conditions are met and you still see no signs of life in the gauge, then it is, as you suspect, faulty. In my experience, this will be either because the needle is stuck in some way or the fault is electrical. You can easily check if the needle is stuck. With the gauge in your hand if you tip it from side, if the needle is free it will swing easily as it does not have a return spring but when mounted correctly the pointer rests on the end stop because of a little weight by the pivot. If this is OK then the fault lies inside and almost certainly will be a broken wire between one of the coils and its binding post.

This gauge is simple yet works remarkable well. With care they are easy to repair and you could save yourself $100!


Shropshire, UK