I have owned my 1966 coupe for 35 years and have never had a problem with the sending unit until yesterday. I ran out of gas 2 blocks from home, but the gas gauge still showed 3/4 full.
Is it possible to test the sending unit without dropping the tank?
Will running some Techron through the tank free it up like it does for the C5 sending units?
Hopefully the sending unit is just stuck and I can free it up somehow.

 

Yes you can test the unit in the tank - sort of. The C2 units, unlike ALL other Corvette generations use a voltage divider arrangement to determine fuel level - a bit of a PITA; here is some info for you: and some 'in car' test methods.

If you can avoid changing out the sender it would be good. The repro sender gaskets are crap - too small and thin. They WILL leak - just a matter of time. Reuse the old one if you have to or try to get an NOS one.....a forum member sent me one gratis when I did this job - God bless him...

QUIZ:

Guess which gasket is NOS and which is repro ?

 

Assuming your sender is an original it can be rebuilt. The individual who does this is John Wolf.

http://www.antiqueinstrument.com/

 

Good luck with that.

 

I had to change mine. I bought a GM authorized new one, not a knockoff (or is it?)for about $80. You need the tool to remove and put back in. I coated the gasket with a little motor oil so it would lube it, making insertion easier. No leaks after a year but I watch it closely.

 

You can do the job without the tool but it sure makes it easier.....the GM-licensed units are made better but still not precisely accurate (none are IMO). If you are SUPER **** you can take out your filler neck and play with bending the float to get the perfect readings....

The problem is the metal sending unit circular retaining ring is a bit small in size and to get it on straight with the hammer and punch method is finicky....the tool obviates this...

 

Some times the winding's separate ( not break ) and float arm gets hung up.Still needs to be repaired. Also I coat float rubber O ring with small amount of oil for ease of installation. And correct tool helps for ease of install

 

Crawl under the car and remove the 2 wires on the sending unit. Hook-up a multi-meter to the two terminals.

Move the float from low to high and multimeter should go from 0 ohms when float is all the way down (empty) and 90 ohms when the float is all the way up (full). For a convertible like I have I can see the float and move it thru this range with a yardstick or my wife's small hand. On a coupe this could get a bitter tricky, and maybe best done with a very low fuel level so you are only trying to pull the float up.........it falls down to almost empty on its own.

For a number of years, the OEM rubber gaskets were hard to get and still are today..........although Ebay has sources for about $20 or so. Recently OEM Reproductions Company has reproduced ones that look very good compared to originals. A few of the Corvette suppliers have them from this company.........but you need to check.

If you must remove the sending unit, it can be done with the tank still in the car. But reuse the metal retaining ring to the tank or buy GM original. They are available (Ebay is one source) and provide the best and most secure fit.........along with the GM rubber gasket.

Good luck in testing. A bad original unit can and should be repaired vs buying a replacement or reproduction.

The fuel gage may have others issues and the tank sending unit is fine. There is a procedure for troubleshooting all in our FAQ or archives.

Larry