1st Generation 1964 1/2 - 1973 - Questions & general discussions that apply to a specific year > 1966 Mustang

1966 fuel sending unit connection ? not working

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Hipo giddyup:
 So I'm really stumped on this one. I have read many posts online  about testing and checking fuel sending units and the fuel gauge and now it looks like I need to head down this path for myself. I never really had any issues with the fuel sending units other than to replace one that no longer works. In the this case its my latest project, a 66' 289 coupe, that has been sitting for a while. The gauge reading was fine before I removed the gas tank for some trunk repairs. However, when I replaced the tank the gauge no longer worked/read anything. I performed the check where you ground the sending unit wire to make sure the gauge responds, and it does. It pegs without issue. So I decided to replaced the dated fuel sending unit. The tank is fairly new but the sending unit, to my knowledge, was reused. I found that it was very corroded and the fuel filter/sock fell apart, so I decided to replace it with an aftermarket unit, a SD. After doing so, nothing. Not registering even with 5 gallons in the tank. So, I drained the tank, pulled the unit and tested it. On my Ohms meter it is reading a range from about 9 Ohms to about 80 Ohms with the range of the arm, and from my research online this should be correct. I then checked the movement of the sending unit outside of the tank. Using a long extension from the tank wire (so I can watch the fuel gauge) I tried moving the unit to make the gauge work. Nothing, then it dawned on me that something needs to be making contact with the vehicle itself. I let the gauge touch the side of the rear windshield molding (what I was close to at the time), and the gauge then gave a decent reading by me manipulating the arm up, then down, etc. This seemed to be working fine. So, I put the unit back in the tank, I cleaned the lock ring to bare metal so as to give a good contact point for the unit to ground to, and replaced about 4 gallons of gas. Uh..., nothing still... Now I'm at a loss. I did use strip caulk between the tank and the trunk lip and now I am wondering if it could be causing the poor connection? I can't imagine this as all of the screws and the one bolt that hold the tank in place are going to metal? Any help on this would be greatly appreciated.

67350#1242:
A quick check would be to run a clip lead from sending unit body to a chassis ground point while mounted in the car.

65Ford:
Perform a continuity check between the ground side of the installed sending unit to the chassis to check for continuity.  If not, break it down by checking between tank and chassis and another from the sending unit to tank.

J_Speegle:

--- Quote from: Hipo giddyup on October 22, 2017, 11:47:40 AM --- I did use strip caulk between the tank and the trunk lip and now I am wondering if it could be causing the poor connection? I can't imagine this as all of the screws and the one bolt that hold the tank in place are going to metal?

--- End quote ---

That should not be a problem. Might just be another defective reproduction

Hipo giddyup:
Good point to do a continuity test. I was fooling with it some more but didn’t have my meter handy. I used a test light, attach the clip to a bare metal portion of the trunk lip (I had sanded to bare metal ) where the tank mounts and touched the sending unit feed/wire. The gauge went to full so I know the ground was good. I then touched the locking ring that holds the sender in place and even touched the metal body of the sender and the gauge stays at E , empty. I would have thought that this would have surely given me a reading? I’ll try the continuity test but it seems like there’s no other option than to pull it out and try to return it?

Can anyone confirm that the ohm readings of 9 -80 of moving the arm one way then the other is a correct range for this sender?

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