You have checked the bulb? I assume so but you do not mention it.

Then if you find the connector at the tank you should be able to bridge out the appropriate pins to 'make the circuit' and test the sender unit?

A quick look on the 'Haynes' looks like light blue and dark blue with black marking wires, light blue being a fused feed and dark blue then off to fuel warning bulb, but just to confuse matters this changes to brown and white in harness before bulb.

The fuel light is fused along with the neutral light and oil pressure light so if those are working the fuse is ok.

So I reckon short out light blue and dark blue at plug and see if light comes on if so then sender at fault, if not trace the wire to where blue becomes brown/white and look for bad joint.

Hope that helps?

Any mishaps fuse No. 4.

Cheers