1985 F250. Can see variable resistance with the fuel sending unit. Float is good. Have blinking voltage at the tank. Truck had 2 tanks, I don't use the rear. The switch in the dash is still hooked up but I removed the powered unit under driver seat that controls which tank. Can't seem to figure out what the problem is.

Could it be the tank switch unit on the frame has to be inline? I disconnected th switch in the dash and nothing changed-can I test somehow what's going on there?

Not sure what to do.

 

Depending on what type of valve you had, yes that could have made the sending unit stop working. Usually the diesels and the 460's had the motorized valve that will cause this problem. If you find the right wires, you can tie them together and get it working again if this is the case.

 

Eureka! Just touched brown wire with yellow/white and the gauge came alive! Thank you. FINALLY. After taking out the sending unit and double checking it, and the float (which I am glad I did), I now know it works.

Thank you!

 

yea my gauge stopped working after my tank selector valve went out. replaced it with one from a junk yard and everything is working great,