I just bought an '86 F250 with dual fuel tanks. I filled the forward one and left the back one nearly empty. By the next morning, both tanks read 1/4 to 3/8s. It appears to have a six way valve, but I am uncertain if this could be the source of the problem. Any suggestions or similar experience?

 

Ford has a problem with a faulty valve, go to this web site and get the recall or tech information

<a href="http://www.nhtsa.dot.gov">http://www.nhtsa.dot.gov</a>/

Dave

 

Common problem. Change the tank switching valve.