BTW, the place on the engine block the sensor should go (where millions of Mustangs have it) will have a 1/4" pipe plug in the hole. Remove the plug and install the sensor, then use the factory plug to stop up wherever the sensor was. Threads should be the same.
Second note: use one turn of teflon plumber's tape on the pipe threads. If you use too much teflon tape, the sensor will certainly not leak but also may be electrically insulated from ground. That may in fact be why your current setup doesn't work. Good luck- J DeRyke