67 Gas tank sending unit.

[Richard S.]

The sending unit in the bottom of the tank has two wire terminals and a ground terminal. The two wire terminals are marked "S" for sender and "I" for ignition, I'm guessing.
Which wire, pink or tan, is connected to which terminal?
If they were connected wrong and the ignition turned on, could that cause the guage in the instrument panel not to function or be damaged? Thanks for the help.

[Joe L.]

Re: 67 Gas tank sending unit.

Rick------

The pink wire goes to the terminal near the center of the fuel sending unit. The tan wire goes to the terminal nearer the perimeter of the sending unit. I don't know how they are marked. Certainly, if the wires are reversed it will cause the gauge to be inoperable. I don't know if such reversal would damage the components in the system.

[Joe L.]

Re: 67 Gas tank sending unit.

Rick------

The pink wire goes to the terminal near the center of the fuel sending unit. The tan wire goes to the terminal nearer the perimeter of the sending unit. I don't know how they are marked. Certainly, if the wires are reversed it will cause the gauge to be inoperable. I don't know if such reversal would damage the components in the system.

[Richard S.]

Re: 67 Gas tank sending unit.

Joe, actually both terminal posts are on the perimeter. One is a little bigger than the other, I guess so they can't be mixed up...but they seem to have been mixed up. Can anyone tell me which terminal post (small or large) gets connected to which lead.(pink or tan) Thanks.

[Richard S.]

Re: 67 Gas tank sending unit.

Joe, actually both terminal posts are on the perimeter. One is a little bigger than the other, I guess so they can't be mixed up...but they seem to have been mixed up. Can anyone tell me which terminal post (small or large) gets connected to which lead.(pink or tan) Thanks.

[John H.]

Re: 67 Gas tank sending unit.

'63-'67 Corvettes were the only GM cars (besides Cadillac) to use the 3-wire fuel sender system; Corvettes before and since use the conventional 2-wire system (tan gauge wire and black ground); the '63-'67 uses the pink (sometimes light green) wire as a 12-volt feed to the sender, the tan wire goes from the sender to the gauge, and the black is ground. Do not connect the pink (or green) wire to the "S" terminal on the sender, as that will fry the resistance element - that wire only goes to the "I" (ignition) terminal. There's a circuit diagram in the 1963 Shop Manual.

[John H.]

Re: 67 Gas tank sending unit.

'63-'67 Corvettes were the only GM cars (besides Cadillac) to use the 3-wire fuel sender system; Corvettes before and since use the conventional 2-wire system (tan gauge wire and black ground); the '63-'67 uses the pink (sometimes light green) wire as a 12-volt feed to the sender, the tan wire goes from the sender to the gauge, and the black is ground. Do not connect the pink (or green) wire to the "S" terminal on the sender, as that will fry the resistance element - that wire only goes to the "I" (ignition) terminal. There's a circuit diagram in the 1963 Shop Manual.

[Richard S.]

Re: 67 Gas tank sending unit.

Well, someone did just that. John, does that mean the sending unit is fryed? Is the instrument guage OK or would it have been damaged too? Do I need to replace the sending unit? Thanks for your help.

[Richard S.]

Re: 67 Gas tank sending unit.

Well, someone did just that. John, does that mean the sending unit is fryed? Is the instrument guage OK or would it have been damaged too? Do I need to replace the sending unit? Thanks for your help.

[Wayne C.]

Re: 67 Gas tank sending unit.

Yes, the fuel gauge unit could have been damaged.

Here are some checks you can run... these assume that you've already checked for end-to-end continuity of the wires in the tank-to-sender circuit, that the black grounding wire end at the tank sending unit actually does have continuity to ground, and that the wires are connected to the correct terminals:

1. Disconnect the tan wire at the tank sender. With ignition switch on, the gauge should now read past the full mark. With the tan wire grounded, the gauge should read empty. If the gauge only goes part way down with the tan wire grounded, then the gauge is likely to be bad.

2. Disconnect all 3 wires at the sender and use a multimeter to check resistance across the two non-ground posts (the ones the pink and tan wires connect to) on the sender. You should read somewhere in the 0-ohm (empty) to 90-ohm (full) range. You can use a long wire with a hook to grab the sending unit float arm through the tank filler neck... moving the arm smoothly through its travel should show a corresponding smooth change in the ohm reading.

[Wayne C.]

Re: 67 Gas tank sending unit.

Yes, the fuel gauge unit could have been damaged.

Here are some checks you can run... these assume that you've already checked for end-to-end continuity of the wires in the tank-to-sender circuit, that the black grounding wire end at the tank sending unit actually does have continuity to ground, and that the wires are connected to the correct terminals:

1. Disconnect the tan wire at the tank sender. With ignition switch on, the gauge should now read past the full mark. With the tan wire grounded, the gauge should read empty. If the gauge only goes part way down with the tan wire grounded, then the gauge is likely to be bad.

2. Disconnect all 3 wires at the sender and use a multimeter to check resistance across the two non-ground posts (the ones the pink and tan wires connect to) on the sender. You should read somewhere in the 0-ohm (empty) to 90-ohm (full) range. You can use a long wire with a hook to grab the sending unit float arm through the tank filler neck... moving the arm smoothly through its travel should show a corresponding smooth change in the ohm reading.

[Richard S.]

Re: 67 Gas tank sending unit.

Wayne, thanks for your reply. Looks like I'll have to replace both units.

[Richard S.]

Re: 67 Gas tank sending unit.

Wayne, thanks for your reply. Looks like I'll have to replace both units.