Fuel Guage Wont Read on Drivers Tank

[86 Silver]

Last year I installed a new fuel tank selector valve as the old one ceased to function. with the new valve came a new pigtail. also i replaced the switch in the cab. anyway, about a month ago, my drivers side tank ceased to read it simply went to way beyone full (about the 3 o'clock position). i thought sending unit so i replaced that on that particular tank. no change. i checked my splicing on the new pigtail and all was solid. however, in messing around down there it would start to work, and then when i shoved all the wires up and way, then it stopped. i couldnt get it to start working again no matter what wires i messed with.

today i followed the wire from the fuel sending unit to the plug on the selector valve and up to the engine. no breaks in the wires. the passenger side tank has never stopped working or reading correctly. the selector valve functions as it should.

someone help!!! why wont my guage read on that drivers side tank!?! it works right on the other tank and as i said all wires are good and connections are solid.

i ran my test light on the pigtail when it was unplugged. the third wire would light up wether i was on switched to the driver or passenger tank. however, when i put the tester in that port it would make the passenger tank guage move, but when i would switch to the driver tank the guage would not move. i have no idea what the hell that means, but i am just sharing what i found.

HELP!!!!