Moss Motors, Ltd

My 1958 Austin Healey BN6 has a problem with the fuel gauge always registering full even when the tank is empty. I put an ohm meter on the fuel sender and found that when the float was raised by hand the reading went from about 5 to 80 ohms.

When the wire between the sender and fuel gauge is disconnected and continuity is checked it shows an open circuit (max. ohms).

With a temporary wire between the sender and fuel gauge a reading of zero is obtained (the tank is empty). When the sender unit is removed from the tank and grounded and the float raised there is no movement from zero on the fuel gauge (ignition is on).

You don't clearly say where you get all these measurements but... Zero to about 80 ohms is correct for the sender. Always reading full suggests a bad sender or broken connection between the gauge and sender. I think you indicated that when checking the continuity. It sounds like a broken wire. You mentioned a reading of zero with a temporary wire between the gauge and sender. Is that zero ohms or empty on the gauge? There is a small possibility of a broken wire or bad connection inside that gauge but it is unlikely if the gauge worked before and you have not opened it. You can test this by grounding the terminal on the gauge that goes to the sender. That should make it go to empty. If not then the gauge is the culprit. If it does then it's the connection between the gauge and sender.

 

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Bayless
Never express yourself more clearly than you can think
'48 Prefect
'67 Sprite (project)