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Discussion Starter · #1 ·
96 7.3 f350 , The truck sat for a couple months while i painted it . with 3 mostly full tanks . After painting , i topped off tanks and started driving to work , after a week or so the fuel filter light came on and the water in fuel light . Drained off the bowl and put new filter in . But the filter light continued to come on from time to time until one day coming home from work it quit . Towed it home , and the next morning it started up no problem . added power sevice 911 to tanks and drove around the block a few times , filter light came on , so i changed filter again , with no luck . a few freinds told me the fuel pump / lift pump was gone so i replaced it and cleaned regulator. awesome , great , runs better than ever . then the fuel filter light started coming on again under load . researched and thought maybe a bio problem so i added power service bio kleen , and drove some more . also gauges dont seem to be reading correctly now , so after a week or so , ( light still coming on but running great ) i topped fuel off . My aux tank was almost empty which is the one i think i have been running on most of this time . But my factory tanks seemed to be pretty much full only took maybe 5 gal between the 2 tanks to fill . Drove for a few more days and i thought i should try the other tanks . When i did filter light came on immediatlely , and shortly after started sputtering . So i switched back to aux tank . Later i tried the other tank with the same results . SO i get it home and figure ok ... the light doesnt come on with the truck at idle so ill let it sit and run on the stock tanks and get that old fuel out . I did ... and went inside .... about 30 minutes later the truck dies . Wont start , so i switch back to aux tank , no luck she still wont start , i have blown the lines out from fron to back and back to front . Chargin my batteries back up now or i would still be out there screwing with it . ANy ideas ?
 

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Check the fuel tank switching valve - under the truck mounted to the frame near the front tank. Sometimes these switches don't fully change position and get stuck. Turn key on - and have someone toggle between front - and back tanks - while you listen and make sure the solenoid is actuating fully in both directions.
 

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yep tried that a little while ago , i could hear the click , also just rerouted fuel lines to bypass switches as mine has 2 , so it would have a direct feed from my aux tank and no luck . I have an xtra cps i am about to change just for Xhits and giggles to rule it out just in case . Then .... i have no idea . Oh i also drained fuel out of front and aux tanks about 5 gal total , thru a paint mixing filter and found no debris . My thinking was maybe see signs of tank liner failure .
 

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Discussion Starter · #4 ·
update : changed cps and the dad gum thing cranked right up . drove it around the block and raised 10 kinds of hell . truck did great . Now i am assuming i still have an issue with my factory tanks so i began to drain the rear tank ...pressurized it with a little air from the return line connected to the tank switch to assist in drain from supply line ... and as i am doing so ... i hear a hissing sound that appears to be coming from the lines on top of the tank ... so next step is to drop the tank , and see what is going on . I am thinking now that my problem maybe a leaky line on the tank sucking air and not supplying enough fuel .... ill let yall know how it goes
 

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Pretty common for the orings in the fittings to need replaced at that age.

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