my fuel gauge in my tach cluster is strating fluctuate and swing around. could that be a bad/dirty ground or a defective fuel sending unit? are those easy to change on a 396 with 3/8" line w/vapor return? i have never dropped a tank.

It could be either. To drop the tank first I'd run it until almost all of the gas is out of the tank. Then look underneath at the two straps that hold the tank up to the body. Unbolt one strap and then unbolt the other where they bolt up to the under body.

Have a floor jack or something ready to catch the tank so it doesn't come crashing down.

Before you get the tank all the way down disconnect the rubber lines. I think I just cut mine as I was going to replace the 30 year old + rubber lines anyways. Don't forget to disconnect the tan colored fuel sender wire.

Then with the gas tank down and on the floor you'll see the sending unit, it's held inside the tank with a big ring that screws into the tank and has teeth on it. I just tapped on the teeth with a hammer and a small pin punch until it freed up, then unscrewed it and took the sender out.

Installation is pretty much the reverse of removal. I'd go ahead and spend an extra $7 and get some gas tank strap silencers so when you put it back on the straps aren't rubbing against the tank and squeaking.

empty the tank first or you`ll be in for a big surprise when you loosen those tank straps !!:thumbsup:

thanks. so how is grounded though? is it where the teeth grab the tank like most of the lightbulbs being grounded where they attach around the metal? how dangerous is all of this with fuel vapor present and needing to test the circuit (so the battery will be connected)?

my fuel gauge in my tach cluster is strating fluctuate and swing around. Better explain the fluctuating and swinging around. With a bad or opening ground, the gauge will fluctuate between reading correctly and past "F". With a short in the sending wire, it will read past "E" If it reads correctly while at a standstill, but the needle moves wildly while driving, the gauge will have to be repaired or replaced.

hey greg, it does stay past Full quite a bit, especially after i fill up. but then it will come down a little as i run around to read near correct. then go back past F by an 1/8" and stay there a while again. that was 2 weeks ago. now it's just staying past F. what do you think?

Bad or open ground. There is a wire from the sending unit to the frame. Check it, make sure it is tight and bolted to clean bare metal. Should be a easy fix.

Could this not also be a loose Nut on the guage completing the circuit at the flexible circuit board?

I ironically have the same problem and was going to tear into it today.

hey greg (or anyone), do i still have to drop the tank to see the ground or is it possible to check this with it normal. i am work and can't look at my car. thanks...

hey greg (or anyone), do i still have to drop the tank to see the ground
No, you do not have to drop tank. Look for a wire comming from top of tank to frame.

A broken or corroded wire between the gauge and the sending unit will do the same thing as a broken or corroded ground--the gauge goes past full.

Since your gauge was going past full at 1/8 tank, I suspect the sending unit itself is corroded--no electrical contact at around the 1/8 tank area. You may be able to clean the sending unit contacts to fix that.

another good idea. thanks. i will try everything i can do with the tank up as i just filled up recently. then drop if i can't fix it that way. i will repost with what transpires.