Question about fuel gauge wiring.
Without this strap the sender cannot ground itself and the gauge will not function. Alternatively, a ground strap can be run from the tank pinchweld to the frame, allowing the sender to achieve ground.
First, there is no "power wire from the sending unit to the dash". You're thinking backwards on this. The dash cluster is powered, with power feeding FROM each of the gauges to their individual sending units, which are nothing more than variable grounds. In the case of the fuel sender, power comes through the wire to the sender which provides variable resistance dependent on float (fuel) level. This is why, if you touch the wire to ground, it will make the gauge register full, like toolmanmike suggested. It goes to ground through the sender body/lock ring/tank, which is still insulated from body ground by the tank straps' rubber insulators and tank pad- so the circuit to ground gets completed by a clip-on ground strap that attaches to the sender barb and the fuel line, "bridging" the short section of rubber hose attached to the sender.
Without this strap the sender cannot ground itself and the gauge will not function. Alternatively, a ground strap can be run from the tank pinchweld to the frame, allowing the sender to achieve ground.
