I have a 1986 silverado with duel tanks, now both tanks read 1/4 full no matter how much gas i put in. can you help

If gauge is pegged full then while driving goes empty then full then 1/2 it is the circuit board inside the fuel tank that has gone bad. to get the tank to register correctly then you must remove tank remove fuel pump module the float arm can be adjusted to read correct level

Sounds like the float in the tank is faulty, or the gauge on the dash.
You should be able to unplug the circuit to the sending unit and check both components.

Bad fuel sending unit.

SOUND LIKE A SENDING UNIT PROBLEM! YOU MAY NEED TO REPLACE IT AT THE TANK!

take the tank down and replace the float on your fuel pump

hi
you have a ground problem check the wiring at the sender it may be broken off or no a good enough ground to the frame it should be a black wire
hope this helps

Your sending unit inside of the fuel tank is probably faulty. Unfortunately you have to drop the tank to change it.

change the sending unit, most are in tank with fuel pump, try to get the whole assembly replaced ,should fix gauge to, hope to help you, thanks robert b.

id say either your sender unit is nackered or you have a bad earth to the body