There is a selector switch which allows you to pick the tank in use and it controls which sending unit is used by the guage. Does the guage show a change when you flip the switch from front to rear tank? There is a fuel tank switching valve underneath on the frame rail. That controls which tank the engine recieve fuel from. I have had to change those before.
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82 F150 LWB 306 cid
83 F150 306 cid
00 Taurus 3.0 OHV
82 Chevy p/u 305 cid
02 C1500 HD 6.0L (Sucks gas)
08 Corrolla S 30-35 mpg  | 
