1973-1991 Dual fuel tank systems theory of operation

[hatzie]

If it was just one tank I'd look at the sender or wiring but this is the same on both tanks. More to the point it's exactly the same on both tanks...

What's the same no matter which tank is selected??? The fuel gauge and the sender wire from terminal B of the valve to the gauge.

Typical Fuel Sender Resistances were within ±3Ω or so on my test gauges from several different years:

• E = 0-3Ω
• ¼= 26-32Ω
• ½= 42-48Ω
• ¾= 61-67Ω
• F = 87-93Ω

¾ is less resistance than F. The only way to get less resistance in this circuit is for the wire insulation to be rubbed through and make an intermittent ground connection. That's unlikely to be repeatable over time.

I'd say it's probably the gauge itself.