Hard Wiring The Fuel Sender Connector

[240260280z]

71 240z resto had bare corroded wires where the fuel sender connectors were supposed to be. Here is the quick and dirty solution:

Step 1:

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

Step 2:

Prepare to solder.

Here are the pillaged parts:

- black wire with bullet connector

- yellow wire with bullet connector

- rubber boots for the solder tails

Step 3:

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.

Step 4:

Seal the boots with silicone

Step 5:

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.

Step 6:

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

Step 7:

The completed connections being tested.

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

Step 8:

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.

Step 9:

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)