ok i took out my front tank today will i be able to run off the rear tank with no problems cause it looks like both tanks are hooked toghter

 

If you have plugged and secured the appropriate fuel lines, made sure the return line to the tank is working, and carefully secured the electrical, yes, you can, but why. Is the front tank toast? Fuel pump or sending unit? If you want to return to the larger capacity, you can change out the rear tank for a 38 gallon tank from aftermarket sources or simply replace the front tank.

 

well im building up my truck and im running a divorced 205 case well the case uses the x member and the tank was in the way so im cutting it down but while i was cutting it down i was going just run on the back tank

 

Yes, it will run fine. Just put a short section of fuel hose over the outlets on the selector valve that went to the tank you removed, clamp them like oyu normally would, then fold the fuel lines over and clamp with another hose clamp. Good enough for the short term. I ran my crewcab for about five months this way because the "new" tank I bought was the wrong one, and there was issues with returning it, and that whole bad customer service experience. I ended up using the old tank, just sealing the small split at the bottom corner.

 

My tank in my 93 f150 was in the box when I bought my truck and parts of the fuel pump hanging on the fuel lines, as long as the front lines hold the pressure of the rear tank lines it should work good

 

Yes, but you do want to cap the lines where the tank is missing. Often enough the crossover valve leaks slightly, allowing fuel from one tank to bleed into the other tank, even if its a miniscule amount. Without the tank for the bleeding to occur, this gasoline is going to just fling into the open air, which aside from being a waste of gasoline, also can be dangerous. Leave your truck idling at a convienence store while you run into to get coffee, and some careless smoker flicks their cigarette out the window and it rolls underneath.... you get the idea.

For the cost of 4" of fuel line and a few clamps, I'd not take the chance.

 

A 1992 truck does not have a crossover valve. That's for pre 1989. The 1989 and up trucks have the supply and return lines "wyed" together.

You must plug both of the lines that used to go to the front tank. The pressure line has 60+ PSI going to it, so something better than fuel hose and worm gear clamps should be used. The return line should be lower pressure.

If the truck went through Ford's "fuel crossflow" recall, there will be a redundant check valve in the pressure line from each tank. If this works and does not leak, and you cut the line on the tank side of the check valve, then the check valve will either block flow out the pressure line or cut the pressure down enough so that something simple could be used to plug the line.

 

Are you sure?

My 93 F350 crewcab has one. I replaced it last year, as it got "stuck" between switching the two tanks (thus neither worked ). Maybe we're not talking about the same thing however ? ? ?

 

My information is based on Ford's TSB's and bulletins for the F-series fuel system, as well as my obsevations of my own 1991 F150.

The early EFI gasoline F-Series (1986 through 1989) had a lift pump in each tank, a transfer valve, and a single high-pressure pump mounted to the framerail. The electrical tank selector switch on the dash commanded the mechanical transfer valve on the frame rail to the appropriate position. The transfer valve on the frame in turn routed the supply and return fuel lines to the approrpiate tank. The transfer valve could get "stuck" between two tanks, giving you no supply at all.

The 1990 through 1993 F-series had a high-pressure fuel pump in each tank, a check valve and shuttle valve in each tank (as part of the "fuel delivery module"), and the supply and return lines were "wye'd" together on the frame rail. There is no mechanical tank selector valve. There is no external high-pressure fuel pump. The tank selector switch is an electrical DPDT switch that routes electrical power from the inertia switch to the appropriate high pressure fuel pump. The other pole of the selector swtich routes the appropriate fuel level sender to the fuel guage.

The 1994 and up F-series vehicles had the same system as 1990 through 1993, although supposedly with "improvements" to the check valve (making them not subject to the NTSB recall).

I note that the 116 and 131 inch wheelbase vehicles had a somewhat different fuel system (at least as noted in the recall). That may explain why your F350 appears to have the older style system. Beyond that, I can't explain your observations.

For anyone trying to diagnose problems, it is fairly easy to crawl under the truck and follow the fuel lines to figure out what type of system you have. The external high-pressure pump should be obvious. The difference between simple "wye" fittings and a mechanical transfer valve should also be obvious.