Fuel sending unit

[roger c]

Hey Guys, I am having a problem with the sending unit on my 58 Impala that I can't seem to figure out. My gauge was not working & always shows just above empty so I disconnected the sending unit then it would show way past full, ground the wire & it shows past empty. I then assumed my gauge was good but the sender is bad so I ordered a repop one. I installed it today & I still have the exact same problem. I tested it before installing it & everything worked as it should, when I move the float arm the needle moved on the gauge just like it should, but after installing it does not work & reads just above empty like the old one did.
There is no pinched or grounded wire & there is a good (tested) ground. I am at a loss here??

What I appear to have here is a sending unit that works outside the fuel tank, but will not work inside the tank???

 

[Don Jacks]

Bob,do you use a ground directly from the battery to the car's body? This sounds like you have a weakground circut,likely due to paint or rust some where between the tank,and the gauge cluster.Just a thought.

 

[roger c]

Ok Guys, I have it working now, however I really didn't do anything that would have fixed it. I have R&R the sending unit 3 separate times. Each time it works exactly right when it is removed from the tank & does not work at all when installed in the tank. I have tried using several different ground locations with no difference. The last time I pulled it out, I took it back to the back deck (where my beer keg is) & studied it for about an hour. I even filled a deep pan with gasoline to check to be sure the float would float & of course it did. Anyway, I put it back in the tank with the screws all loose so I could wiggle it a little, had my wife check the dash gauge & it was working. I tightened it up & now it works. I still don't know what the problem was??? I'm 67 years old, been a mechanic since 1962 & have never seen anything like this before. I even took a flashlight & looked in the sending unit hole to see if there was some kind of obstruction inside the tank & there wasn't. I have been working on this since 9:00 this morning & just finished up about 30 minutes ago.

Don, Thanks for your comment, I did check the wires & used those very same wires to test it with when it was removed from the tank & it worked just fine. I had made up my mind that if it didn't work this last time, I was just gonna carry a 2 gallon gas can in the trunk & live without the gauge.

 

[chevymusclecars]

Do you have a ground wire running to the outside of the sending unit? If not try a jumper wire from the ring holding the sending unit in place to ground and see if that works. Some cars had it and some didn't but it makes it more reliable.

Bill