Well here is what I have found....Senders/sensors/tramsmitters/switches, whatever you want to call them sometimes need a to complete or make a ground to work right. There are some multiple wire senders that use one wire as a ground, but I think all 1 wire senders need that ground. If you use teflon tape it's possible to get too good of a seal and not have any metal on metal contact for a ground or just not enough. The teflon dope is probably good, just use enough to whet the threads and allow squeeze-out to permit a good ground.Also teflon tape shouldn't be eaten away, it's kinda permanant. Also with small brass pipe thread fittings, if you use the tape you run the risk of splitting the fitting when you tighten it up enough to keep it from moveing.