Hard Wiring The Fuel Sender Connector

Pillage the 280z 2+2 wiring harness that I bought from Jim Karst many moons ago (THANKS JIM)

Prepare to solder.

Here are the pillaged parts:

- black wire with bullet connector

- yellow wire with bullet connector

- rubber boots for the solder tails

Solder the leads:

note:

- the yellow lead carries the voltage and attaches to the pin with the elevated stand off (insulator)

- the black lead is the return and is at ground potential. (not insulated and connected to the metal cover)

- when soldering; ensure that the pins are thoroughly scraped/sanded down to exposed shiny brass metal, as well; ensure that sufficient heat is applied to the grounded pin so that the solder flows well and no cold solder joint occurs.

Seal the boots with silicone

Solder a second set of new leads with bullet connectors to the wiring harness:

In this photo, the new leads are on the right and the harness is on the left. I was unable to scavenge a yellow lead so I used a black with yellow tracer stripe.

The wires are now joined and soldered. Note the heat-shrink ready to be positioned.

The completed connections being tested.

note: the bullet connectors at the harness are for the fuel pump.

The harness is now in position. I used the front deck grommet for the fuel leads and the back grommet for the rear ground lead.

The fuel sender leads come through the floor just behind the fuel sender neck.

How the sender works:

1. 12V is applied to a b-imetal switch in the dash's fuel gauge then continues back to the gas tank via the yellow wire.

2. The fuel sender in the tank has a float that rises and falls with fuel level. As the float moves, it also changes the resistance in the circuit to the bi-metal heater.

- The fixed side of the fuel sender's rheostat is connected to the yellow lead and is insulated

- The variable side (wiper) of the fuel sender's rheostat is connected to the black lead and is grounded

- As the float rises, the wiper effectively brings the ground closer to the yellow lead. This decreases the resistance in the bimetal circuit. This inturn causes quicker heating of the bi-metalstrip and pushes the indicator in the gauge towards the full side.

- As the float falls, the wiper travels further from yellow lead. This increases the resistance in the bimetal circuit. This inturn causes slower heating of the bi-metalstrip and does not push the indicator as much thus the the gauge moves towards the empty side.

3. Resistance of fuel sender typically ranges from 10ohm to 80ohm (full/empty)