Fuel gauge

[Doug 63]

The fuel gauge on my '63 isn't functioning. It bounces a bit off the bottom peg (on the empty side). Possibilities for this include:
Bad gauge
Bad sender
Leaky float
Wiring short between the sender and gauge
What I'd like to do is troubleshoot the gauge before digging into the tank to check out the sender and float. I can check the wires (and so far I'm convinced they're okay). But I was wondering if anyone knew of a way to test the gauge before I open the fuel tank and mess with the sender and float. Is there a way to apply different resistors on the sender end to see if the gauge responds? If so, does anyone know what resistance I should use? I am assuming that the sender just varies the resistence between the sender and the ground.

 

[bk65]

Hey Doug,

The fuel gauge reads full when the send is at high resistance (mine reads about 50 ohms) and reads empty when the resistance is low (mine reads about 4 ohms). I think there is a previous message where someone actually had the exact numbers. I believe it was either 0-60 ohms or 0-90 ohms.

There are two wires that connect to the gauge, one is a wire that is hot when the ignition is on (the schematic says it's pink), and the other wire (brown)comes back through the fuse box and travels on to the sending unit. Then the sending unit is grounded with black wire. At any rate, whats happening with your gauge is the wire from the gauge to the sending unit is shorting to ground at some point. Disconnect the brown wire from the tank. Your gauge should read full. If it still jerks toward empty then the short is not in the send but either in the line from the fuse box to the tank or from the fuse box to the gauge. If it stops jerking then it's in the send.

My gauge had been jerking toward full (meaning there was an open in the circuit rather than a short) turned out the ground wire wasn't making a good connection.

Hope this helps,

 

[Doug 63]

The latest:

Replaced the sender, float, and gasket. Now the gauge works but with a full tank it only reads 3/4 full. A little more fiddling I guess.