Dual Gas Tanks??

[reliabilty]

Just purchased a 68 custom cab F100. Has the 390 motor with dual gas tanks. The owners said the front tank doesn't work. Any body know why it wouldn't?

[peanutman]

Are you meaning tank behind the seat as the front tank I am sure there are members on here than can tell you a lot more than me. Several pointers, you should have a switch -over valve down on floorboard driverside between door and seat, that could be froze up, you should also have a toggle switch below ignition switch that controls your senders in each tank.
I would check all that out. If tank hasen't been used in a while i would pull it and check for gunk, rust and holes before i used it.
Also check all your lines, That switch -over valve at side of driverside seat- you can see line configuration if you crawl under truck and look, pretty simple setup. Someone here can give you additional advise if i missed something.

[reliabilty]

Yea that's the one...the one behind the seat. I'll check those out...Thanks!

[peanutman]

Yea that's the one...the one behind the seat. I'll check those out...Thanks!

Po may have disconnected your switch-over valve as well, i hear you can take those apart if froze up and get them working again.

[fordman]

make sure its hooked up. check it for rust holes. and then put some gas in it. he might have been talking about the guage not working in it for all you know.

[mr50s]

This is my first post on the Fordification website. Sure hope someone can help me. I've got a 1970 For XLT half-ton with an in-cab tank as well as an auxiliary tank located between the frame rails. The tank switch valve located on the floor of the cab between the seat and driver's door leaks like mad. It looks like one could replace a seal located just under the operating handle for this valve. The valve stem measures 5/16th of an inch, i believe. What seal material should I use? Who sells it? Website name? How much is it? I ask all this because it will have to withstand today's fuels, and will have to seal completely without failing. Also, my dashboard tank switch isn't working. How can I clean it safely and test to see if it's good or not?

Elsewhere, I've been told I need to replace the vacuum modulator unit on my C-6 automatic in this truck. Trouble symptoms include mis-timed upshifts at normal throttle when accelerating, very surge-y idle but smooth operation at all other throttle settings, and accumulation of automatic trans fluid on the intake manifold behind and below the 2-barrel carburetor. How do you remove and replace this modulator? Can anything accidentally fall inside the tranny when you remove the old one? Is it okay to trust an aftermarket modulator from just any chain parts store, or is a certain brand preferable? How much is it? What is the name or website name?

Thanks in advance for any help you can give. Maybe Fordification can pull me through!!

Mr50s

[fordman]

the floor valve should just have some o rings or something similar in it. the modulator is bad if you are getting fluid on the manifold. it is held on by a tab with a screw. clean out any dirt that may fall in the hole when yo utake it off. you may also need a new vacuum line where the fluid is leaking out of it on the intake. i dont knwo about the switch. it is just a switch. you could try unpluggin it and trying a different switch. just to see if that is the problem

[scott123]

The floor valves are easy rebuild. The mounting screws being frozen are the hardest part.

The dash switch can be rebuilt but the more likely culprit to a fuel gauge not working is the sending unit. There are test procedures somewhere on this site. Basically ground the signal wire and if the guage reads full its the sender.

To rebuild it take it out of the tank and pry back the tabs/ ears that hold it together. (Bend them as little as poss as they will break off VERY EASILY!!!!) Use a dremel with a soft brass wire wheel or fine wet dry sand paper and clean the wires on the board. Re-assemble, Done.

Sidebar: Some switches come greased. If you have a 30+ year old switch the grease can dry out and form an insulator between contacts. Disassemble , clean, re grease and re-assemble. Done