MF 135 UK fuel gauge?

[Arc weld]

I was trying to clean some dirt out of the fuel tank on my 1965 UK 135 diesel. I've had my problems with the fuel gauge being intermittent for a while too. I took the sending unit out in the process and it looked in perfect shape. I have a cab and couldn't see the fuel gauge. Anyway, with the tractor running I measured the volts at the sending unit and it was only around 3.6 volts and the fuel gauge read a little above empty. It had about 3-3 1/2 gallons of fuel in it. When I shut it off, the fuel gauge went down below empty about 3/16" which I think means it's working but not sure? I thought maybe just taking the connections off at the sender and putting them back may have been all it needed? I've read fuel gauges have their own voltage regulator and the sending unit uses a variable resister so I'm wondering, does the sending unit vary the voltage to tell how much fuel is in the tank? I didn't have anyone to look at the gauge while I was at the sending unit and just trying to figure out how it works. It might be OK now but I won't know till I fill it up again.

 

[EssexBoy]

The fuel gauge gets its power from the voltage regulator (+) post (4) and the fuel sending unit (ground) so yes the sending unit is a variable resister.

 

[Harry in Ky]

If you can remove the sender, you can test it without help. You will need some jumper wires, one long enough to allow you to connect the sender wire to the terminal on the unit and have the unit in hand while in a position to view the gauge. Another jumper to connect the base of the unit to chassis ground. With the gauged powered up, you should be able to move the float rod up and down slowly and see the needle move accordingly. It should move smoothly with no skips or jerks. provided the float unit is performing properly. No meters or test equipment required.