My '84 had the empty to 1/4 full fuel gauge syndrome so I searched, followed what others have done and found the float shaft had rust. Of course the rust would not allow the float to rise beyond the point corresponding with the 1/4 mark. Gentle work with emery cloth, some PB Blaster, thorough rinsing, reassembly and works great. This vehicle had not moved for ??? so it certainly made sense.
Steve

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Steve
'87 300TD - 132K - Soon 4-Sale
'84 300D Turbo - 122K - Driving
'77 VW Type II - 77K - Restored
'08 250EX Ninja
English Bulldog (Brier) - My best friend. Passed away 12/02/04 while in my arms.