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Another fuel gauge problem PLEASE HELP!


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Hello well im new to the forums and i have spend the whole afternoon looking for answer in this forums and i only found 1 post with my same problem but no way to fix it

Well I got my 72 Z back in december and been working on it since then, my fuel gauge was working fine when i first got it but later i had to remove the gas tank due to some leakeage on the hoses,well after replacing all the hoses on the rear end and placing the tank back my fuel gauge was only reading to 1/2 tank it been 4 month since then so today i decided to replace my sending unit since according to some post thats seems to be the problem sometimes (i did check that the fuel gauge was working by grounding the yellow cable and i was getting a full tank reading)i got my new sending unit and tested outside the tank and it was working fine but after i installed in the tank and filling it up at the gas station still only reads to 1/2 tank so i went back under the car and like some post said that the connector go bad as well so i repladed those with new female spade connectors and still reads only to 1/2

so PLEASE if anyone knows anything about fixing this problem let me know it will be Very appreciated

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is the float on the sender all there?

It's been too many years since I have had a sender/float out of a Z, but I had a similar problem with my truck a couple of years ago (69 Chevy).

The float would take on fuel and constantly read a quarter tank. Bought a new float and it's been fine. Did your new sender come with a new float?

when you tested it outside the car did you simulate the full range of motion for the arm, or possibly bend it putting it back in? Also check the sender with an ohm meter to make sure the signal is smooth.

Good luck man.. If you were closer (Fullerton is about 4 hours from me) I would try to help..

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the float is there it all comes together and i was extra extra careful of not bending or messing up the sender when i was putting it back in the tank.

well i guess i will probably have to drop the tank again to see if there is anything inside the tank that is causing this problem and at the same time im gonna try to put some isolation in the gas tank straps since in the only post that i found about this same problem they said that doing so it may fix the issue since appears that there is a grounding problem when the straps have full contact with the tank

well thanks for replying to my post

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The two wires going to the sending unit complete the circuit from the fuel gage. No further grounding is required as long as your proper ground on the chassis is in good shape. That ground is located on the right hand side of the car (and I presume either RHD/LHD) and it's just aft of the opening leading to one of the drain holes on the hatch floor.

As far as adjustment, the sending unit has one adjustment. That's the position of the sliding contact to the float lever. When you take your sender out, look at it from the bottom portion of the "circuit". You'll note that there is a piece of circuit board material wound with some wire that has a sliding contact . That sliding contact will travel from one end of the wound coil to the other. It doesn't go all the way end to end, the float can't go UP high enough nor DOWN low enough to reach the extremes of the wires.

Now look at the pivot point for the float lever, you'll note that there is a screw fixing the position of the sliding contact with the float arm. Determine the sender's proper alignment (there's a notch on it's metal plate that aligns with the fuel tank's opening) and compare where the float would be at "empty" and "full" and adjust your sliding arm accordingly.

If additional fuel gage adjustments need to be made, there is some amount of electrical adjustment that can be made at the gage, but the problem is that it's tricky to fill the tank, get in there, adjust the gage to "full", then empty the tank, and once again check the gage, and repeat.... The adjustment at the gage is there, but I have not played with it to give you more detail, and I'll leave it to others to perform the gymnastics required to adjust via that method.



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Before you put the new sender in the tank, did you hook it up to the two wires that go to the guage/ground and test it manually? Did the guage indicate full when the float/arm is held all the way up? Can't see how installing it in the tank could change it unless the fuel is not holding the float/arm up as high as when you manually test it out of the tank.

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