7T1vette

I'm still trying to figure out how the OP determined that "the sending unit is not the culprit", given that the sender ground wire has no effect in the circuit?????

Either the ground wire is broken inside the insulation, or it is not making actual electrical contact with the frame OR with the metal body of the sender. The other option (the one I am favoring) is that the sending unit is defective. Just how did you determine that it was OK?

Brcmpbl

Hi, this is a thread I started over a year ago, and I'd say my original post isn't entirely accurate anymore. I'm just testing everything now.

For what it's worth, I replaced the original sending unit with a new one a couple of years ago, and the fuel gauge acted the same with both senders. With both the most it would read when full is just above half.

Brcmpbl

So I ran a jumper ground from the sending unit prong to the frame, and the gauge did not change at all. It certainly seems like the ground has no impact on the gauge at all. The gauge passes the other tests, and the sender gives a resistance reading.

Not sure what to do next except put my new gauge in and see what happens.

Brcmpbl

This saga is ongoing - or maybe not. Today I decided to do what I should have done long ago but inexplicably didn't - I stuck a rod into the tank and pulled the float arm all the way to the top with the key on in the ignition, and the gauge moved up to a full reading. I feel like I fill the tank when I put gas in the thing - but the needle is never more than a hair over half. I'll feel pretty silly if I've just not been filling this thing for the past 4 years.

Admittedly, this is the only Corvette I've had with the leaded gas style open filler neck - my 77 and 76 and others of course were closed style necks.

7T1vette

Fill the tank to just below the neck opening. If you try to fill it more, you can get a lot of splash-back. If you haven't been filling it up close to the neck, that's likely your problem. You will know at your next fill-up.

Brcmpbl

Thanks 7T1. I headed to the local gas station after I posted, and I put the most gas in the tank that I ever have. That netted me 3/4 tank, which is the highest I've ever seen the gauge go. That was about 3 inches or so from the bottom of the filler neck, maybe a little more.

7T1vette

Then your gauge reads as expected. I fill mine to within 1/2" of that neck. I suspect that if you did that, the gauge would read higher...but not up to the "Full" mark.

You might need to reach in with a sturdy piece of metal or smooth wooden dowel and bend the float down a bit, so that the sender would get better travel when full. But, what it reads when Full is not nearly as important as having it read Empty when you still have 2-3 gallons left in the tank.