1988 f350 7.3 diesel dual tanks

Here is the deal. Bought the truck and fuel gauge said 1/4 tank. didnt move at all. Started tracing wires and and had gauge cluster out and gauge went to 1/2 where it stays now. Im pretty sure sending unit is bad on both tanks per nothing on ohm meter. Jumped wires on sending unit plugs and still nothing. Checked ground to frame on front tank and good. Pulled plug on selector valve and jumped wires yellow/blue to yellow, and blue/yellow to yellow at seperate times. nothing. nothing on any switch position. pulled lines off of both tanks and switched valve and fuel is returning to proper tank and pulling from each tank( let it run out of fuel with each line unpluged) so at least my selector valve is working. Would you think the gauge is bad? only the volt gauge and speedo works and backlights come on with headlights on. Getting about 10v to selector. a used gauge is $50 hate to drop that kinda cash on it and it not work. there only brown and red wires on dash selector switch so i figured wire from valve goes straight to plug on back of gauge cluster. thanks.

 

Could be the gauge cluster or bad connection at the plug on the rear, or even a bad trace on the circuit on the rear.

 

Bad trace ? Rear what? Picked up a cluster at parts yard for $37 gonna try it.

 

UPDATE. Gauge cluster replacement gave me all way to full and now crossing wires on sender gives me empty. Pulled both sending units out of the tanks and the metel is worn off where the finger sweeps on the board. That explains the OL reading on one and 1.4kohms on other. Small round sender in back. I cant find these any where. any one have a source or an idea of another model that will work. Think a '85 or 6 460 truck looks pretty close but pic shows place for intank pump. should jus be able to put my wires on sender plug and not use the tabs for pump. ideas?

 

Ok since i work for.advance auto part time i looked at the.spectrum fuel sending unit picture book. Ordered part FG39A looks close to mine but with intank pump. Cut one "ear" off of truck wiring plug and it will plug up to the connection using the two.right hand connection tabs. Presto my fuel gauge works and sweeps.from full to empty as i move the float and has the lines facing the correct way. Now to figure out a part to replace the small round faulty one in the rear plastic tank. I will have to add a piece of hose (im using 30r9 FI rated hose) to extend tube to bottom of tank.

 

Update. Final installation went well. Decided to extend pickuptube with steel line and compression fitting so the rubber line wouldnt flop around and interfear with the float. Gauge reads a little past full but i can live with that.

 

Glad to hear you found a solution!!