Troubleshooting Fuel Quantity System per Willcox Instructions

I’ve been troubleshooting my fuel quantity system using the guidance from Willcox Corvette’s website.

Problem: The gauge never reads below 2/3 full. When I top off the tank, the gauge reads beyond the full level almost to the 2 o’clock position.

Trouble shooting per Willcox directive:

• Voltage to gauge and sender is good.
• Disconnecting ohm’s wire: Gauge reads at 3-4 o’clock position. Checks good.
• Grounding ohm’s wire to frame: Gauge reading stopped at ½ tank. The reading was supposed to go to “empty”.
• Checking sender continuity. Checks good.
• Checking ground wire to frame continuity. Checks good.
• Checking sender resistance (tank was almost full): Read 85 ohms, a full tank should read 90 ohms.

I tried to hook the sender float arm with a grounded wire but for the life of me I couldn’t hook the float to move it down to see if the fuel gauge reacted to it. I plan to drive the car to nearly empty then re-measure the sender resistance to confirm the float arm is not sticking at an intermediate position.

I’m thinking I might have a faulty sender or perhaps the resistor at the fuel gauge is faulty or weak.

I sent an inquiry to Willcox but have not heard back yet. I would appreciate your best guestimate.

Thanks,
Tom

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Troubleshooting Fuel Quantity System per Willcox Instructions