I need the electrical diagram for 1990 F250 dual gas tanks

SOURCE: I have a 90 F250

the diverter valve that shuts the flow off to fuel tank, and transferes over to other tank is bad. here is a picture of it--1990 f250 valve.

SOURCE: '96 f150,4.9 six,dual fuel tanks,replaced front

I have a 1996 f150 and I had the same problem. I finally found out that the rear fuel pump is the main pump, and if it goes out then the front pump will not work either. There is a groud that both pump share on the rear cross member. If you are not getting good connection with the ground the fuel pumps will not work. Also if you replace the rear pump and it still does not work then your problem could be the fuel tank selector switch, it acts as a relay if it goes out then neither pump will work.

Marvin

• 85242 Answers
• Posted on Oct 31, 2011

SOURCE: Rear Fuel tank doesnt work so my 1990 ford f 150

Hello
Having worked for Ford for 25 years and having seen this very same problem (fuel flows between tank and overflows) many times there is only one cause of the fuel flooding the other tank, the fuel switching valve on the frame rail under the truck is detective, this valve contains special silicone rubber poppet valves that open when the front or wear tank fuel pump is selected, it then seals when the tanks electric pump is shut off at the selector switch, your poppet valves are leaking, all to a common problem. Back in 2000 when I retired this switching valve was no longer sold by Ford parts, it is obsolete. I suggest you check with Ford to see if it is available from some other source or call a local parts store like NAPA or Carquest and inquire is anyone in the aftermarket has them. The last choice is a used one, but of course it could have the same problem as yours as age and deterioration of the rubber valves is what makes them leak.