Classic/Antique Car Repair: fuel sending unit problem, fuel sending unit, ranchero

Question
I Have a 68 Ranchero. I installed a new sending unit in the tank. The unit works ok out of the tank, when i install it the gauge goes to full. Although the tank is only half full. It seems to ground to the tank. Any ideas on what the problem is? Any help will be greatly appreicated. Thanks John.

Answer
I think you have correctly diagnosed the problem, that the sender wire is somehow getting grounded.  Either the float is sticking up to the top of the tank somehow (very unlikely) or else the sender wire is bare and somehow touching metal somewhere.  Just inspect the wire carefully, you should be able to find it.

You could have someone watch the gauge while you loosen the wire at the sender to see if the gauge drops while you fiddle with it - maybe it's caught on something where you can't see it.  

This is a job for a detective - I doubt very much there is anything else wrong.

Good Luck -and Good hunting!

Dick