Fuel system mystery

[jbrown1969us]

I am a new member here and I have tried to search out similar problems and found none so far. I am hoping someone can help me figure this out.
Truck is a 93 F-250 7.3 idi with dual tanks and 142,000. I replaced the fuel filter late last year. Mechanical fuel pump in January of this year.
My issue started last November on the rear tank before replacing the fuel pump. Fuel filter light came on only at highway speeds and it would not get enough fuel. Only on rear tank, front tank was fine, figured clogged pick up tube.
Recently my fuel gremlin seems to jump from tank to tank. Neither tank will usually get above 1,500 RPM. But some days the rear tank works to about 2,000 and other days the front tank.
Always seems to be opposite tanks. I am thinking multiple issues of course, but I am leaning towards the FSV as my primary culprit. Mainly because sometimes flipping back and forth between tanks will help one tank. Other times it does nothing .
Thoughts anyone???

 

[icanfixall]

Welcome to the forum. My guess is your fuel change valve is sticking because some of the old suction screens are getting sucked in and trapped internally. you can open this valve by drilling out the rivets but will need self tapping screws to put it back together

 

[jbrown1969us]

Sorry it took me so long to get back to this. Been a very hectic last few months and I completely forgot to reply.
I took the control valve apart and cleaned it up really good, helped some. I then blew air through the lines from the valve to the tanks. Took care of the problem with the front tank. I can run 80mph with no issue.
The rear tank will act up once in a while. Usually if it gets lower than a half tank.
Until I get other bugs worked out, and drop the rear tank. I am primarily on the front tank.
Thank you again for your help and once again, I apologise for the late reply.

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