Originally Posted by IanH

Fuel gauge is relatively simple. Assuming the voltage is correct at the cluster i.e. other gauges are fine, you only have the sender in the tank and the gauge head.
There is normally a way to check the gauge head in the cluster by shorting and opening the sender unit. On other cars when you do this the needle lines up with little white marks on gauge face. I don't know if Nissan is the same, cant find it in the FSM Factory Service Manual, see sticky at top of B14 section.

See FSM page 91 in EL section to test resistance of the sender. Measure the resistance, should be full at 36 ohms and empty at 129 Ohms.

So if you put this target resistance in place of the sender the gauge head will read full at 36 ohms and empty at 129 Ohms.

A Final comment, if your odometer and fuel gauge are both bad it may be time you looked for a replacement cluster. Got mine with matching milage on odometer for $50.

Hope this helps, good luck........