Fuel Gauge Malfunction

[jackf]

So it's been a few weeks since I drove my 73 coupe. I filled the tank before I parked it, and fuel gauge needle was on "F".  This morning on start, needle on fuel gauge was as far right as possible, way beyond the "F".  Any ideas of where to start?

Thanks,

jack

 

[Galucha]

Sounds like the sending unit wire is being grounded out somewhere. If you pull the plug off of the sending unit on the tank side, does the needle go back down to empty? 

 

[jackf]

So when key is off, needle is on E.  When key is on, needle is way past F.  Turn key off, goes back to E.  Pull connector, needle is on E.  I read resistance from sending unit (aftermarket put in a couple of years ago) and it reads 9.8 ohms. I assume I have about 3/4 of a tank currently.  Thanks for the reply.

 

[TheRktmn]

Needle would be on or just past E at 10 ohms.  3/4 is about 16 I believe. 

If the needle does not not max out when disconnected from sender then it's in the sender or gauge. 71-73 have plastic housings so it's not the gauge stud grounding.  That leaves sender or printed circuit on back of cluster, but I would expect that to be unaffected by the sender disconnect. Sounds to me like a bad sender.