my 98 blazer 4x4 has around 145,000 miles on it and recently my fuel gauge started to act wierd. like i fill it up to full and when it gets to around 3/4 or below when i start my truck it goes crazy up and down to full to 1/2 and so on and so on. up and down and so on. what can cause this ??????? its driving my nuts....

 

could be a bad sending unit or bad wiring... at 145k I'd estimate a bad sending unit...just watch your mileage and leave it until the pump dies and replace it all at once then...