I just hooked up a old and proven sender to the gauge ground (Brown wire from gauge in trunk at latch), and grounded the sender to body. Turned the ignition on and I can watch the gauge move while moving the float up and down. So I at least know the gauge and the circuit to it is good.
Disconnecting the brown wire to my simulation sender (open circuit), the gauge races up and past full. Just like the one in tank when disconnected. So I'm assuming there is at least a continuity down to my new sender.
Its almost like the new sender float leaked, has fallen off or the mechanism is stuck or jammed on empty.
A poor ground (increased resistance) would only cause the needle to rise, no ground, it would go past full. 0 ohms at empty, 90 at full.
Next. Attempt to raise the float through the filler and see if the gauge moves.
Regardless, the tank probably has to come down again.
Bummer. It's no fun dropping a tank, especially when it's full. Again...
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65 Laurentian post, 67 Grande Parisienne 4 door HT.
The thought just occurred to me that the brown wire as it is strung across the tank to the sender post...could be pinched by the tank, or is shorted to ground somewhere.
No resistance would set the gauge at empty as GM designed.
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65 Laurentian post, 67 Grande Parisienne 4 door HT.
Good diagnosis Mark. The wire should sit in an indentation on the top of the tank, often held by a couple pieces of tape. It should be halfway protected, but you know how that goes.
