the fuel baffle tube / pick up contains the sensor for fuel level
find the plug for this coming from the top of tank, un plugg it.
the end that goes to towards the main harness, jump the two wires together.
pink and pink and black me thinks, dont quote me tho.
with these jumped, push start button with lanyard off to power up gauges
this should send gauge to a full reading, if it does, then the sensor assy in pick up tube is bad.
i have seen on here people repairing a fuse on the circuit board on the assy.
never tried this,
good luck
mud