1971 F250 Question (Fuel Gauge problem)?

ok simple fix,or troubleshoot.ground the wire from the sending unit.a buddy can confirm it reading fuel when grounded.if the sending unit wire doesnt produce a full reading when its grounded, then step 2.find the wire going to the dash,should be same colors.shave wire and use a jumper to ground.it should read full.if not, its the guage most likely.if it read full at the tank,its gonna be the sender.you may have a resistor in the instrument panel,that slows the electricity to get rid of the erratic guage operation from sloshing.you might get a schematic, itll save you tons of time, but the fix is similar for all vehicles and is easy especially with a schematic.

john it sounds to be a ground problem by the tank or on the top of sending unit i have had the same problem once before ... unless if this is a restore project then check the sending to the guage

your problem has many achievable motives .locate the gasoline sender unit {often on the precise of the gasoline tank} examine if there is any wires related if not attempt and locate them. if there is disconnect the single interior the centre and attempt shorting to earth if the gauge is going up the sender is defective if not achievable broken twine and or fuse. or you need to take it to an motor vehicle electrician to fault discover and fix.

i would check fuses and if that dont work it has to b the fuel sending unit in the tank...