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Discussion Starter #1
Hey everyone. I have been chasing a grounding problem for some time on my 67. I have installed a few senders hoping to resolve the issue. When I pull the sender out of the tank and just connect the ground it works the dash fine. As soon as I install it the needle pegs at full. Some how its grounding. Any assistance would be great.. My one thought.. Is the tank supposed to be isolated from the chassis via the tar strips and the rubber insulators on the straps? Please help.. Thanks everyone.
 

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Any thoughts on what is going on?? I have tried 3 sender units so far.. Frustrating as I do not know how much fuel I have.. Thanks
 

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Nope.. Power into the insulated plug on the sender.. It has a tail as a ground.. I have also checked that.. As noted it is not until I close the lock ring down on the sender that it stops working and grounds out.. I even thought what if the pick up was hitting the bottom of the tank possibly? Again any help / advise appreciated as this problem is a year old and I am really getting tired of this..:mad: Thanks Bill
 

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Pretty stupid question; but I can't think of anything else that would cause you problem: You do have the rubber o-ring seal installed....Correct ????
 

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Discussion Starter #7
I hear ya Tony.. I am pulling my hair out.. Like everything else I am sure its installed correctly.. But... Something is touching somewhere.. Thanks for the response.. Let me know if you think of anything else!!
 

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How 'bout a break or cut in the wire somewhere between the tank and the gauge ????
(Particularly where the wire comes through the grommet in the floor beneath the back seat....)
 

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Discussion Starter #9
I checked continuity as well as voltage. Even ran a slave wire to make sure.. So it sits at full because something is grounding.. If I disconnect it to goes to empty.. You have be thinking about the rubber seal.. I think I am going to take the sender out and check it.. Sometimes that thing wanders when I tighten the ring.. Will let you know.. Thanks for your persistence.
 

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On a chevy, the needle going to full indiactes LOSS of ground.

As crazy as it sounds and seems, your sending unit is LOOSING ground.

I had the same problem on my 76 recently, when I swapped in a tank from a 77 firebird. I had the foresight to check the sending unit before I installed the tank, and it worked fine. AFTER the tank was in, it didn't work anymore. I dropped the tank back out, reinstalled the sending unit, and it worked fine again.
 

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Discussion Starter #11
Firebird.. Thanks much.. I am on vacation but will get on taking it out and re-installing .. Will see.. thanks!!
 

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Use your multimeter to help you figure it out.

set to ohms, and check for continuity between the 'hot' post and the ground flag. You should see it change from ( near ) zero to about 50 as you move the float arm up and down.
 

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I would look at the wire going to the guage. It may be gounding somewhere. Your gound is not the issue. Your signal wire is going ground somewhere. The signal wire that plugs into the sending unit should be insulated on top to ensure it is not touching the metal.
 

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Discussion Starter #15
Thanks guys.. I will take a look at these items.. I have run an external new wire from the gauge to the sender thinking also that the wire was grounding. Didnt do anything.. I have been working with my meter to check when it goes bad.. Its always when to tighten the ring for the sender in the tank.. Will get into it again and see what I can find out..
 

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I would look at the wire going to the guage. It may be gounding somewhere. Your gound is not the issue. Your signal wire is going ground somewhere. The signal wire that plugs into the sending unit should be insulated on top to ensure it is not touching the metal.
EXCEPT that as I pointed out.. on older chevy the guage pegs out past full when there is NO ground.. so check the wire to make sure it does not have any breaks ( open ) If it were grounding, it would be showing empty.
 
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