It may be the fuse.. I unknowingly reconnected mine the way it looked like it should go, but instead connected it wrong and blew the gauge's fuse! If a mechanical gauge is really that easy to install, I need to go get one since I'm rolling around without one...
The wire looks like it should contect to the metal tab sticking out the top of the sending unit when infact it should connect down on the bottom of the tab (sorry, I know there are probably more technical terms I coul dbe using....)
Thread dredge, because I just did this, and it is NOT plug and play, exactly, on an 86-
the sender's 1/8" BSP (British Standard Pipe) which IS 27 tpi but is ever so slightly
smaller in diameter than the NPT we use.
So the 1/8" fitting wouldn't thread into the sender hole.
You need a 1/8" BSP sender (electric) or 1/8" fitting (mechanical) to hook one up.
Made a big puddle as the filter drained while I tried (without success) to screw in a 1/8 NPT fitting.
Eventually I finally measured the sender, whacked self in head, and made up a quickie adaptor.